Bacteria frofiles.docx

Bordetella pertussis

Bordetella pertussis
Bordetella pertussis on charcoal agar. Very small colonies after 5 days of cultivation in aerobic atmosphere, 35°C.
Bordetella pertussis is the causative agent of pertussis or whooping cough. Pertussis is an infection of the respiratory system and characterized by a "whooping" sound when the person breathes in. Worldwide in 2000, according to the WHO, around 39 million people were infected annually and about 297,000 died. The infection occurs most with children under the age of one when they are unimmunized or children with faded immunity, normally around the age 11 through 18.






Klebsiella pneumoniae

Klebsiella pneumoniae

Klebsiella pneumoniae on Endo agar. Large, mucous colonies after 24 hours of cultivation in aerobic atmosphere, 37°C.
As a general rule, Klebsiella infections tend to occur in people with a weakened immune system. Many of these infections are obtained when a person is in the hospital for some other reason (a nosocomial infection). The most common infection caused by Klebsiella bacteria outside the hospital ispneumonia. Klebsiella ranks second to E. coli for urinary tract infectionsin older persons. It is also an opportunistic pathogen for patients with chronic pulmonary disease, enteric pathogenicity, nasal mucosa atrophy, and rhinoscleroma. Feces are the most significant source of patient infection, followed by contact with contaminated instruments.



Streptococcus pneumonia

Streptococcus pneumoniae
Streptococcus pneumoniae on blood agar in detail. Cultivated 24 hours in an aerobic atmosphere enriched with 5% carbon dioxide, 37°C.
Streptococcus pneumoniae is part of the normal upper respiratory tract flora, but, as with many natural flora, it can become pathogenic under the right conditions (e.g., if the immune system of the host is suppressed). 
S. pneumoniae is normally found in the nasopharynx of 5-10% of healthy adults, and 20-40% of healthy children. It can be found in higher amounts in certain environments, especially those where people are spending a great deal of time in close proximity to each other (day care centers, military barracks).

Streptococcus pneumoniae




Streptococcus pneumoniae

Streptococcus pneumonia

Virulent strain of Streptococcus pneumoniae on blood agar. Cultivated 48 hours in an aerobic atmosphere enriched with 5% carbon dioxide, 37°C.
Despite the name, the organism causes many types of pneumococcal infection other than pneumonia, including acute sinusitis, otitis media, meningitis, bacteremia, sepsis, osteomyelitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis, and brain abscess. S.pneumoniae is the most common cause of bacterial meningitis in adults and children, and is one of the top two isolates found in ear infection, otitis media.





Neisseria meningitidis

Neisseria meningitidis
Growth of Neisseria meningitidis on a selective medium for pathogenic neisseriae. Some strains form pearl-like colonies on the surface of this media. Cultivation 24 hours in an aerobic atmosphere enriched with 5% carbon dioxide, 37 °C.
Neisseria meningitidis exists as normal flora in the nasopharynx of up to 5-15% of adults. It causes the only form of bacterial meningitis known to occur epidemically. Meningococci only infect humans and have never been isolated from animals because the bacterium cannot get iron other than from human sources (transferrin and lactoferrin).
N. meningitidis is a major cause of morbidity and mortality during childhood in industrialized countries and is responsible for epidemics in Africa and in Asia. Approximately 2500 to 3500 cases of N. meningitidis infection occur annually in the United States, with a case rate of about 1 in 100,000. Children younger than 5 years are at greatest risk, followed by teenagers of high school age. Rates in sub-Saharan Africa can be as high as 1 in 1000 to 1 in 100.



Streptococcus pneumoniae

Streptococcus pneumoniae
Streptococcus pneumoniae cultivated on blood agar aerobically, 5% CO2, overnight. Zones of alpha-hemolysis around colonies.
On blood agar, encapsulated pneumococci produce round, glistening colonies surrounded by a zone of alpha-hemolysis. The colonies often develop a dimpled, then a craterlike appearance (autolysis).
Microscopy:
Gram-positive, non-motile, encapsulated, oval diplococci(lancet shape)



Haemophilus influenzae

Haemophilus influenzae
Haemophilus influenzae on chocolate agar. Cultivated 24 hours in an aerobic atmosphere enriched with 5% carbon dioxide, 37°C.
H. influenzae was mistakenly considered to be the cause of influenza until 1933, when the viral etiology of the flu became apparent.
Most strains of H. influenzae are opportunistic pathogens; that is, they usually live in their host without causing disease, but cause problems only when other factors (such as a viral infection or reduced immune function) create an opportunity. 
In infants and young children, H. influenzae type b (Hib) causes bacteremia, pneumonia, and acute bacterial meningitis. On occasion, it causes cellulitis, osteomyelitis, epiglottitis, and infectious arthritis. Hib remains a major cause of lower respiratory tract infections in infants and children in developing countries where the vaccine is not widely used.
Microscopy:
Small, Gram-negative, non-motile rods that tend to assume a coccobacillary shape
Klebsiella pneumoniae

Klebsiella pneumoniae
Mucous, lactose positive colonies of Klebsiella pneumoniae on MacConkey agar. Cultivation 37°C, 24 hours.
As a general rule, Klebsiella infections tend to occur in people with a weakened immune system. Many of these infections are obtained when a person is in the hospital for some other reason (a nosocomial infection). The most common infection caused by Klebsiella bacteria outside the hospital is pneumonia. Klebsiella ranks second to E. coli for urinary tract infections in older persons. It is also an opportunistic pathogen for patients with chronic pulmonary disease, enteric pathogenicity, nasal mucosa atrophy, and rhinoscleroma. Feces are the most significant source of patient infection, followed by contact with contaminated instruments.
Microscopy:
Gram-negative, non-motile, encapsulated, rod shaped bacterium.

Klebsiella pneumoniae

Klebsiella pneumoniae
Large (about 5 mm in diameter), lactose positive colonies of Klebsiella pneumoniae on desoxycholate-citrate agar. Cultivation 37°C, 24 hours.
Klebsiella pneumoniae is a common source of hospital-acquired infections. Some of the strains can carry plasmids that harbour genes conferring resistance to almost all antibiotics. These bacteria are called multiresistantor, informally, superbugs or super bacteria.
Among these bacteria many different Enterobacteriaceae species were identified, including Citrobacter freundii, Enterobacter cloacae,Escherichia coli, Klebsiella oxytoca, Morganella morganii, Proteus spp.,Providencia spp.. Most isolates remain susceptible to colistin andtigecycline (natural resistance to colistin in M.morganii, Proteus spp. and Providencia spp. !!).
Microscopy:
Gram-negative, non-motile, encapsulated, rod shaped bacterium.

Mycobacterium tuberculosis

Mycobacterium tuberculosis
Mycobacterium tuberculosis on Löwenstein-Jensen medium. Cultivated five weeks in an aerobic atmosphere, 37°C.
Mycobacterium tuberculosis (MTB) is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis. First discovered in 1882 by Robert Koch, M. tuberculosis has an unusual, waxy coating on the cell surface (primarily mycolic acid), which makes the cells impervious to Gram staining so acid-fast detection techniques are used instead.
Tuberculosis usually attacks the lungs but can also affect other parts of the body. It is spread through the air when people who have an active MTB infection cough, sneeze, or otherwise transmit their saliva through the air. Most infections in humans result in an asymptomatic, latent infection, and about one in ten latent infections eventually progresses to active disease, which, if left untreated, kills more than 50% of its victims.
Microscopy:
Slim, rod-shaped, acid-fast bacterium (difficult to stain with commonly used basic aniline dyes at room temperature)



Mycobacterium fortuitum

Mycobacterium fortuitum


Mycobacterium fortuitum on blood agar. Cultivated 9 days in an aerobic atmosphere, 37°C.
Mycobacterium fortuitum has a worldwide distribution and can be found in natural and processed water, sewage, and dirt. It is uncommon for it to cause lung disease. M. fortuitum can cause local cutaneous disease, osteomyelitis (inflammation of the bone), joint infections, and occular disease after trauma. It is a rare cause of lymphadenitis. M. fortuitum can be a nosocomial (hospital acquired) disease. Surgical sites may become infected after the wound is exposed directly or indirectly to contaminated tap water. Other possible sources of M. fortuituminfection include implanted devices such as catheters, injection site abscesses, and contaminated endoscopes.


Microscopy:
Acid-fast rods.


Streptococcus pyogenes
Group A streptococci

Streptococcus pyogenes
Colonies of Streptococcus pyogenes cultivated on blood agar. Cultivation 24 hours in an aerobic atmosphere enriched with 5% carbon dioxide. Colonies are surroundend by a zone of beta-hemolysis.
Streptococcus pyogenes is a spherical, Gram-positive bacterium that is the cause of Group A streptococcal infections. S. pyogenes displays streptococcal group A antigen on its cell wall. S. pyogenes typically produces large zones of beta-hemolysis (the complete disruption of erythrocytes and the release of hemoglobin) when cultured on blood agar plates, and are therefore also called Group A (beta-hemolytic) Streptococcus (abbreviated GABHS).
Microscopy:
Spherical or ovoid cells in chains of short to medium length (4-10 cells).
Streptococcus pyogenes
Group A streptococci

Streptococcus pyogenes Group A streptococci
Large colonies of Streptococcus pyogenes cultivated on Columbia agar with 5% sheep blood. Cultivation 24 hours in an aerobic atmosphere enriched with 5% carbon dioxide. Colonies are surroundend by a zone of beta-hemolysis.
Streptococcus pyogenes is the cause of many important human diseases, ranging from mild superficial skin infections to life-threatening systemic diseases. Infections typically begin in the throat or skin. Examples of mild S. pyogenes infections includepharyngitis ("strep throat") and localized skin infection ("impetigo"). Erysipelas and cellulitis are characterized by multiplication and lateral spread of S. pyogenes in deep layers of the skin. S. pyogenes invasion and multiplication in the fascia can lead to necrotizing fasciitis, a potentially life-threatening condition requiring surgical treatment.
Microscopy:
Spherical or ovoid cells in chains of short to medium length (4-10 cells).


Streptococcus agalactiae

Streptococcus agalactiae
Group B streptococci
Colonies of Streptococcus agalactiae cultivated on Columbia agar with 5% sheep blood. Cultivation 24 hours in an aerobic atmosphere enriched with 5% carbon dioxide. Colonies are surroundend by a zone of beta-hemolysis.
Streptococcus agalactiae is a member of the gastrointestinal normal flora in some humans and can spread to secondary sites - including the vagina in 10–30% of women. This is of clinical importance: S. agalactiae can be transferred to a neonate passing through the birth canal and can cause serious group B streptococcal infection. In the western world, S. agalactiae is the major cause ofbacterial septicemia of the newborn, which can lead to death or long-term sequelae.

Microscopy:
Spherical or ovoid cells in chains of short to medium length.

Escherichia coli

Escherichia coli cultivated on blood agar. Cultivation 24 hours in an aerobic atmosphere, 37°C. Colonies are without hemolysis but many strains isolated from infections are beta-hemolytic.
Escherichia coli is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some, such as serotype O157:H7, can cause serious food poisoning in humans. The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and by preventing the establishment of pathogenic bacteria within the intestine. 
Virulent strains of E. coli can cause gastroenteritis, urinary tract infections, and neonatal meningitis. In rarer cases, virulent strains are also responsible for haemolytic-uremic syndrome, peritonitis, mastitis, septicaemia and Gram-negative pneumonia.
Microscopy:
Gram-negative, motile, rod-shaped bacterium.



Escherichia coli

Escherichia coli
Escherichia coli cultivated on MacConkey agar. Lactose positive colonies. Cultivation 24 hours in an aerobic atmosphere, 37°C.
Escherichia coli is the most common cause of urinary tract infections. Uropathogenic E. coli (UPEC) is responsible for approximately 90% of urinary tract infections (UTI) seen in individuals with ordinary anatomy. In ascending infections, fecal bacteria colonize the urethra and spread up the urinary tract to the bladder as well as to the kidneys (causing pyelonephritis), or the prostate in males. Because women have a shorter urethra than men, they are 14-times more likely to suffer from an ascending UTI.

Microscopy:
Gram-negative, motile, rod-shaped bacterium.




Staphylococcus aureus

Staphylococcus aureus
Staphylococcus aureus, Columbia agar with 5% defibrinated sheep blood. Cultivation 24 hours, aerobic atmosphere, 37°C. Colonies are surroundend by a wide zone of beta-hemolysis.
Staphylococcus aureus is frequently part of the skin flora found in the nose and on skin. About 20% of the human population are long-term carriers of S. aureus.
S. aureus can cause a range of illnesses from minor skin infections, such as pimples, impetigo, boils (furuncles), cellulitis folliculitis, carbuncles, scalded skin syndrome, and abscesses, to life-threatening diseases such as pneumonia, meningitis, osteomyelitis, endocarditis, toxic shock syndrome (TSS), chest pain, bacteremia, and sepsis. Its incidence is from skin, soft tissue, respiratory, bone, joint, endovascular to wound infections. It is still one of the five most common causes of nosocomial infections, often causing postsurgical wound infections.

Microscopy:
Gram-positive cocci, nonmotile, tend to be arranged in grape-like clusters.


Stenotrophomonas maltophilia

Stenotrophomonas maltophilia
Colonies of Stenotrophomonas maltophilia on Mueller-Hinton agar. Cultivation 72 hours, aerobic atmosphere, 28°C.
Stenotrophomonas maltophilia frequently colonizes breathing tubes such as endotracheal or tracheostomy tubes, the respiratory tract and indwelling urinary catheters. Infection is usually facilitated by the presence of prosthetic material (plastic or metal), and the most effective treatment is removal of the prosthetic material (usually a central venous catheter or similar device). The growth of S. maltophilia in microbiological cultures of respiratory or urinary specimens is therefore sometimes difficult to interpret and not a proof of infection. If, however, it is grown from sites which would be normally sterile (e.g., blood), then it usually represents true infection. In immunocompetent individuals, S. maltophilia is a relatively unusual cause of pneumonia, urinary tract infection, or blood stream infection; in immunocompromised patients, however, S. maltophilia is a growing source of latent pulmonary infections.S. maltophilia colonization rates in individuals with cystic fibrosis have been increasing.
Microscopy:
Smaller (0.7-1.8 μm long),Gram-negative, motile, rod shaped bacterium.

Chryseobacterium indologenes

Chryseobacterium indologenes
Colonies of Chryseobacterium indologenes on Mueller-Hinton agar. Cultivation 72 hours, aerobic atmosphere, 28°C. C. indologenes is inherently resistant to tetracycline.
Colonies of Chryseobacterium indologenes are deep yellow due to the production of the water-insoluble pigment flexirubin. The natural habitats ofChryseobacterium are soil, plants, foodstuff, and water sources, including those in hospitals. It rarely has clinical significance. C.indologenes has been documented to cause bacteremia in hospitalized patients with severe underlying disease. Nosocomial infections due to C.indologenes have been linked to the use of indwelling devices during the hospital stay.

Microscopy:
Smaller ,Gram-negative, motile rods.



Mycobacterium sp.

Mycobacterium sp.
Colony of Mycobacterium sp. on Ogawa medium. Cultivation 10 days, aerobic atmosphere, 28°C. An example of rapidly–growing mycobacterium.
Mycobacterium is a genus of Actinobacteria, given its own family, theMycobacteriaceae. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis (Mycobacterium tuberculosis) and leprosy (Mycobacterium leprae).
All Mycobacterium species share a characteristic cell wall, thicker than in many other bacteria, which is hydrophobic, waxy, and rich in mycolic acids/mycolates. The cell wall consists of the hydrophobic mycolate layer and a peptidoglycan layer held together by a polysaccharide, arabinogalactan. The cell wall makes a substantial contribution to the hardiness of this genus.
Mycobacteria are widespread organisms, typically living in water (including tap water treated with chlorine), soil and food sources.

Microscopy:
Acid-fast rods.


Campylobacter jejuni

Campylobacter jejuni
Colonies of Campylobacter jejuni. Cultivation 2 days, microaerophilic atmosphere, 42°C. Spreading along the streak line is commonly seen. Hemolysis on agar with sheep blood is not observed.
Campylobacter jejuni is a species of curved, helical shaped, non-spore forming, Gram-negative microaerophilic, bacteria commonly found in animal feces. It is one of the most common causes of human gastroenteritis in the world. Food poisoning caused by Campylobacter species can be severely debilitating, but is rarely life-threatening.
Contaminated food is a major source of isolated infections, with incorrectly prepared meat and poultry normally the source of the bacteria. Infection with C. jejuni usually results in enteritis, which is characterised by abdominal pain, diarrhea, fever, and malaise. The symptoms usually persist for between 24 hours and a week, but may be longer. Diarrhea can vary in severity from loose stools to bloody stools. The disease is usually self-limiting.

Microscopy:
Curved, S-shaped ("gull-shaped"), or spiral Gram-negative rods. May form spherical or coccoid bodies.
Pasteurella multocida

Pasteurella multocida
Colonies of Pasteurella multocida on blood agar. Cultivation 24 hours, aerobic atmosphere, 37°C. P. multocida colonies on 24-h blood agar plates are 1 to 3 mm in diameter and nonhemolytic.
It can cause a zoonotic infection in humans, which typically is a result of bites or scratches from domestic pets. Many mammals and fowl harbor it as part of their normal respiratory microbiota, displaying asymptomatic colonization. P. multocida is the most common cause of infection from animal injuries (pneumonia in cattle and pigs, atrophic rhinitis in pigs and goats, andwound infections after dog/cat-bites.) A high leukocyte and neutrophil count is typically observed, leading to an inflammatory reaction at the infection site (generally a diffuse localized cellulitis). It can also infect other locales, such as the respiratory tract. In more serious cases, a bacteremia can result, causing an osteomyelitis or endocarditis. The bacteria may also cross the blood-brain barrier and cause meningitis.

Microscopy:
Gram-negative, non-motile coccobacilli or rods.

Enterobacter sakazakii

Enterobacter sakazakii
Enterobacter sakazakii on Endo agar. Cultivation 24 hours, 37°C. Colonies are yellow pigmented and often have quite typical "leathery consistence" on Endo agar.
Enterobacter sakazakii is an opportunistic pathogen in humans. It is a rare cause of invasive infection with historically high case fatality rates (40–80%) in infants. It can cause bacteraemia, meningitis and necrotising enterocolitis. E. sakazakii infection has been associated with the use of powdered infant formula, with some strains able to survive in a desiccated state for more than 2 years.

Microscopy:
Gram-negative, motile rods.




Serratia marcescens

Serratia marcescens
Colonies of Serratia marcescens . Cultivation 24 hours, 37°C. Some strains of Serratia marcescens produce a red pigmented, prodigiosin.
An opportunistic human pathogen, Serratia marcescens is involved in nosocomial infections, particularly catheter-associated bacteremia, urinary tract infections and wound infections, and is responsible for 1.4% of nosocomial bacteremia cases in the United States. It is commonly found in the respiratory and urinary tracts of hospitalized adults and in the gastrointestinal system of children. Due to its ubiquitous presence in the environment, and its preference for damp conditions, S. marcescens is commonly found growingin bathrooms (especially on tile grout, shower corners, toilet water line, and basin), where it manifests as a pink discoloration and slimy film feeding off phosphorus-containing materials or fatty substances such as soap and shampoo residue. Once established, complete eradication of the organism is often difficult, but can be accomplished by application of a bleach-based disinfectant. Rinsing and drying surfaces after use can also prevent the establishment of the bacteria by removing its food source and making the environment less hospitable.

Microscopy:
Gram-negative, motile rods.
Moraxella catarrhalis 
(Branhamella catarrhalis)


Colonies of Moraxella catarrhalis on blood agar. Cultivation 24 hours, 37°C. Colonies are nonhemolytic.
Clinically, these bacteria are known to cause otitis media, bronchitis, sinusitis, and laryngitis. Elderly patients and long-term heavy smokers with chronic pulmonary disease should be aware that M. catarrhalis is associated withbronchopneumonia, as well as exacerbations of existing chronic obstructive pulmonary disease (COPD). The peak rate of colonisation by M. catarrhalisappears to occur at approximately 2 years of age, with a striking difference in colonization rates between children and adults (very high to very low). M. catarrhalis has recently been gaining attention as an emerging human pathogen. It has been identified as an important cause in branchopulmonary infection, causing infection through pulmonary aspiration in the upper pulmonary tract. Additionally, it causes bacterial pneumonia, especially in adults with a compromised immune system. It has also been known to cause infective exacerbations in adults with chronic lung disease, and it is an important cause inacute sinusitis, maxillary sinusitis, bacteremia, meningitis, conjunctivitis, acute purulent irritation of chronic bronchitis, urethritis, septicemia (although this is rare), septic arthritis (which is also a rare occurrence), as well as acute laryngitis in adults and acute otitis media in children.

Microscopy:
Gram-negative diplococci, nonmotile.

Bacillus cereus


Large colonies of Bacillus cereus on blood agar. Cultivation 24 hours, 37°C. Colonies are surroundend by a wide zone of beta-hemolysis.
Bacillus cereus is an endemic, soil-dwelling, Gram-positive, rod-shaped, beta hemolytic bacterium. Some strains are harmful to humans and cause foodborne illness, while other strains can be beneficial as probiotics for animals. It is the cause of "Fried Rice Syndrome". B. cereus bacteria are aerobes, and like other members of the genus Bacillus can produce protective endospores.

B. cereus is responsible for a minority of foodborne illnesses (2–5%), causing severe nausea, vomiting and diarrhea. Bacillus foodborne illnesses occur due to survival of the bacterial endospores when food is improperly cooked. Cooking temperatures less than or equal to 100 °C (212 °F) allows some B. cereus spores to survive. This problem is compounded when food is then improperly refrigerated, allowing the endospores to germinate. Germination and growth generally occurs between 10–50 °C (50–122 °F), though some strains are psychrotrophic. Bacterial growth results in production of enterotoxins, one of which is highly resistant to heat and to pH between 2 and 11; ingestion leads to two types of illness, diarrheal and emetic (vomiting) syndrome.

Microscopy:
Gram-positive, spore-forming rods.
Bacillus mycoides

Bacillus mycoides
Rim of a colony of Bacillus mycoides on Mueller-Hinton agar. Cultivation 72 hours, 28°C. Soil isolate.
Ubiquitous in nature, Bacillus includes both free-living and pathogenic species. Under stressful environmental conditions, the cells produce oval endospores that can stay dormant for extended periods. These characteristics originally defined the genus, but not all such species are closely related, and many have been moved to other genera. 

Microscopy:
Gram-positive, spore-forming rods.



Listeria monocytogenes

Listeria monocytogenes
Small colonies of Listeria monocytogenes on blood agar. Cultivation 24 hours, 37°C. Listeria monocytogenes is beta-hemolytic on sheep blood agar plates but often produce only narrow zones of hemolysis that frequently do not extend much beyond the edge of the colonies.
Listeria monocytogenes is the causative agent of listeriosis. It is one of the most virulent foodborne pathogens, with 20 to 30 percent of clinical infections resulting in death. Responsible for approximately 2,500 illnesses and 500 deaths in the United States annually, listeriosis is the leading cause of death among foodborne bacterial pathogens, with fatality rates exceeding even Salmonellaand Clostridium botulinum. 

Due to its frequent pathogenicity, causing meningitis in newborns (acquired transvaginally), pregnant mothers are often advised not to eat soft cheeses, which may be contaminated with and permit growth of L. monocytogenes. It is the third most common cause of meningitis in newborns.

Microscopy:
Gram-positive, asporogenous, motile(at 28°C), short rods.

Corynebacterium pseudotuberculosis

Corynebacterium pseudotuberculosis
Small colonies of Corynebacterium pseudotuberculosis on blood agar (2 mm in diameter). Cultivation 72 hours, 37°C.
Corynebacterium pseudotuberculosis is phylogenetically closely related toCorynebacterium diphtheriae, may also harbor the diphtheria toxin gene. C. pseudotuberculosis is positive for urease and the reverse CAMP test (complete inhibition of the effect of Staphylococcus aureus beta-hemolysin on sheep erythrocytes). It can cause lymphadenitis(occupational), ulcerative lymphangitis and abscess formation.

Microscopy:
Gram-positive, asporogenous, nonmotile rods. "Coryneforms".



Yersinia enterocolitica

Yersinia enterocolitica
Small, lactose negative colonies of Yersinia enterocolitica on Endo agar (1-2 mm in diameter). Cultivation 24 hours, 37°C.
Yersinia enterocolitica infection causes the disease yersiniosis which is a zoonotic disease occurring in humans as well as a wide array of animals such as cattle, deer, pigs, and birds.
Acute Y. enterocolitica infections usually lead to mild self-limitingenterocolitis or terminal ileitis in humans. Symptoms may include watery or bloody diarrhea and fever. After oral uptake yersiniae replicate in the terminal ileum and invade Peyer's patches. From here yersiniae can disseminate further to mesenteric lymph nodes causing lymphadenopathy. Ths condition can be confused with appendicitis and is therefore calledpseudoappendicitis.

Microscopy:
Gram-negative, asporogenous, motile rods or coccobacilli.


Neisseria gonorrhoeae

Neisseria gonorrhoeae
Non-hemolytic colonies of Neisseria gonorrhoeae on a medium with sheep blood. Cultivation 48 hours, 37°C, 5% CO2.
Neisseria gonorrhoeae is a species of Gram-negative coffee bean-shaped diplococci bacteria responsible for the sexually transmitted infection gonorrhea. Symptoms of infection with N. gonorrhoeae differ depending on the site of infection. N. gonorrhoeae can also cause conjunctivitis, pharyngitis, proctitis or urethritis, prostatitis and orchitis. Conjunctivitis is common in neonates (newborns), and silver nitrate or antibiotics are often applied to their eyes as a preventive measure against gonorrhoea. Disseminated N. gonorrhoeae infections can occur, resulting in endocarditis, meningitis or gonococcal dermatitis-arthritis syndrome. Infection of the genitals in females with N. gonorrhoeae can result in pelvic inflammatory disease if left untreated, which can result in infertility. Infertility is a risk to 10 to 20% of the females infected with N. gonorrhoeae.

Microscopy:
Gram-negative, non-motile diplococci with adjacent sides flattened (a coffee bean appearance)
Pseudomonas sp.

Pseudomonas sp.
Yellow pigmented colonies of Pseudomonas sp. on Mueller-Hinton agar. Cultivation 72 hours, 28°C.
Pseudomonas species are widespread in nature. The members of the genus demonstrate a great deal of metabolic diversity, and consequently are able to colonise a wide range of niches. Their ease of culture in vitro and availability of an increasing number of Pseudomonas strain genome sequences has made the genus an excellent focus for scientific research. Pseudomonas have theability to metabolise a variety of diverse nutrients. Combined with the ability to form biofilms, they are thus able to survive in a variety of unexpected places. A simple carbon source, such as soap residue or cap liner-adhesives is a suitable place for them to thrive. 

Most Pseudomonas spp. are naturally resistant to penicillin and the majority of related beta-lactam antibiotics.

Microscopy:
Gram-negative, motile, asporogenous, rod-shaped bacterium.

Vibrio parahaemolyticus

Vibrio parahaemolyticus
Colonies of Vibrio parahaemolyticus on Thiosulfate-citrate-bile salts-sucrose agar (TCBS agar). Large colonies after prolonged cultivation 48 hours in aerobic atmosphere, 37°C.
Vibrio parahaemolyticus is a bacterium found in brackish saltwater, which, when ingested, can cause gastrointestinal illness in humans. Outbreaks tend to be concentrated along coastal regions during the summer and early fall when higher water temperatures favor higher levels of bacteria. Seafood most often implicated includes squid, mackerel, tuna, sardines, crab, shrimp, and bivalves like oysters and clams. The incubation period of ~24 hours is followed by explosive, watery diarrhea accompanied by nausea, vomiting, abdominal cramps, and sometimes fever. Vibrio parahaemolyticus symptoms typically resolve with-in 72 hours, but can persist for up to 10 days in immunocompromised individuals. As the vast majority of cases of V. parahaemolyticus food infection are self-limiting, treatment is not typically necessary. In severe cases, fluid and electrolyte replacement is indicated. Additionally, swimming or working in affected areas can lead to infections of the eyes or ears and open cuts and wounds.

Microscopy:
Gram-negative, motile, asporogenous, rod-shaped bacterium.
"Streptomyces coelicolor" A3(2)
Streptomyces violaceoruber

"Streptomyces coelicolor" A3(2)
Streptomyces violaceoruber
Colonies of "Streptomyces coelicolor" A3(2) on Mueller-Hinton agar. Cultivation 14 days, 28°C. The bacterium produces antibiotic actinorhodin (blue pigment colouring colonies and surrounding cultivation medium). Production of actinorhodin takes place when cultures of S. coelicolor A3(2) enter the stationary phase. Colonies are covered with white aerial mycelium with spores.
The complete genome of "S. coelicolor" strain A3(2) was published in 2002. At the time, the S. coelicolor genome was thought to contain the largest number of genes of any bacterium. The chromosome is 8,667,507 bp long (Escherichia coli 4,639,221 bp) with a GC-content of 72.1%. Taxonomically, "S. coelicolor"A3(2) belongs to the species of Streptomyces violaceoruber and not a validly described separate species; "S. coelicolor" A3(2) is not to be mistaken for the actual Streptomyces coelicolor (Müller).

Microscopy:
Gram-positive, non-motile, rod-shaped bacterium. Produces spores.
Streptomyces spp.

Streptomyces spp.
Streptomyces spp. on various cultivation media. Production of different pigments and formation of aerial mycelia. Colonies after approximately 15 days of cultivation in aerobic atmosphere, 28°C. Environmental isolates.
Streptomyces is the largest genus of Actinobacteria and the type genus of the family Streptomycetaceae. Over 500 species of Streptomyces bacteria have been described. As with the other Actinobacteria, streptomycetes are gram-positive, and have genomes with high guanine and cytosine content. Found predominantly in soil and decaying vegetation, most streptomycetes produce spores, and are noted for their distinct "earthy" odor which results from production of a volatile metabolite, geosmin.
Streptomycetes are infrequent pathogens, though infections in human such as mycetoma can be caused by S. somaliensis and S. sudanensis.

Microscopy:
Gram-positive, non-motile, rod-shaped bactera. Produce spores.



Citrobacter freundii

Citrobacter freundii
Lactose positive colonies of Citrobacter freundii on MacConkey agar. Cultivation 24 hours, aerobic atmosphere, 37°C. Approximately 20% of clinical isolates are lactose negative.
These bacteria can be found almost everywhere in soil, water, wastewater, etc. It can also be found in the human intestine. They are rarely the source of illnesses, except for infections of the urinary tract and infant meningitis and sepsis. C. freundii strains have inducible ampC genes encoding resistance to ampicillin and first-generation cephalosporins. In addition, isolates of Citrobacter may be resistant to multiple other antibiotics as a result of plasmid-encoded resistance genes.

Microscopy:
Gram-negative, motile rods.



Salmonella enterica

Salmonella enteric
Lactose negative colonies of Salmonella enterica ssp.enterica (serotype Enteritidis) on MacConkey agar. Cultivation 24 hours, aerobic atmosphere, 37°C.
Most cases of salmonellosis are caused by food infected with S. enterica. Raw chicken eggs and goose eggs can harbor S. enterica, initially in the egg whites, although most eggs are not infected. As the egg ages at room temperature, the yolk membrane begins to break down and S. enterica can spread into the yolk. Refrigeration and freezing do not kill all the bacteria, but substantially slow or halt their growth.

Microscopy:
Gram-negative, motile rods.




Klebsiella pneumoniae andSalmonella enterica

Klebsiella pneumoniae andSalmonella enteric
Lactose positive colonies of Klebsiella pneumoniae (larger) and lactose negative colonies of Salmonella enterica ssp.enterica (serotype Enteritidis) on McConkey agar. Cultivation 24 hours, aerobic atmosphere, 37°C.

Microscopy:
Gram-negative, non-motile(K.pneumoniae) and motile(S.enterica)rods.





Salmonella enterica ssp.enterica

Salmonella enterica ssp.enterica
Colonies of Salmonella enterica ssp.enterica (serotype Enteritidis) on blood agar. Cultivation 24 hours, aerobic atmosphere, 37°C.
Most cases of salmonellosis are caused by food infected with S. enterica. Raw chicken eggs and goose eggs can harbor S. enterica, initially in the egg whites, although most eggs are not infected. As the egg ages at room temperature, the yolk membrane begins to break down and S. enterica can spread into the yolk. Refrigeration and freezing do not kill all the bacteria, but substantially slow or halt their growth.

Microscopy:
Gram-negative, motile rods.



Chryseobacterium indologenes
and an actinomycete

Chryseobacterium indologenes
and an actinomycete
Colonies of Chryseobacterium indologenes (yellow) and an actinomycete (orange)on Mueller-Hinton agar. Cultivation 72 hours, aerobic atmosphere, 28°C.

Microscopy:
Gram-negative, motile rods and nonmotile, Gram-positive rods..





Enterococcus faecalis

Enterococcus faecalis
Colonies of Enterococcus faecalis on blood agar. Cultivation 24 hours, aerobic atmosphere, 37°C. Colonies are nonhemolytic.
Enterococcus faecalis – formerly classified as part of the Group DStreptococcus system – is a commensal bacterium inhabiting the gastrointestinal tracts of humans and other mammals. Like other species in the genus Enterococcus, E. faecalis can cause life-threatening infections in humans, especially in the nosocomial (hospital) environment, where the naturally high levels of antibiotic resistance found in E. faecalis contribute to its pathogenicity. E. faecalis can cause endocarditis, as well as bladder, prostate, and epididymal infections; nervous system infections are less common.

Microscopy:
Gram-positive, ovoid, nonmotile cocci.



Providencia rettgeri

Providencia rettgeri
Providencia rettgeri on Endo agar. Cultivation 24 hours, 37°C. Lactose negative colonies.
An opportunistic pathogen in humans. It can cause urinary tract infections, particularly in patients with long-term indwelling urinary catheters or extensive severe burns.

Microscopy:
Gram-negative, motile rods.






Morganella morganii ssp. 
morganii

Morganella morganii ssp. 
morganii
Morganella morganii ssp. morganii on blood agar. Cultivation 24 hours, 37°C.
It causes a disease known as Summer Diarrhea. Morganella morganii, being a member of the tribe Proteae of the family Enterobacteriaceae, is a Gram-negative bacillus with two subspecies: M. morganii and M. sibonii. This bacterium is found in the environment and in the intestinal tract of humans and other organisms. There are several symptoms that this bacterium can cause: sepsis, ecthyma, endophthalmitis, choirioamnionitis, and more commonlyurinary tract infections, skin and soft tissue infections, meningitis, and septic arthritis.

Microscopy:
Gram-negative, motile rods.


Micrococcus luteus


Micrococcus luteus
Micrococcus luteus on columbia horse blood agar. Cultivation 48 hours in an aerobic atmosphere, 37°C.
Micrococcus luteus is a Gram-positive, spherical, saprotrophic bacterium . An obligate aerobe, M. luteus is found in soil, dust, water and air, and as part of the normal flora of the mammalian skin. The bacterium also colonizes the human mouth, mucosae, oropharynx and upper respiratory tract. M. luteus is coagulase negative, bacitracin susceptible, and forms bright yellow colonies on nutrient agar. To confirm it is not Staphylococcus aureus, a bacitracin susceptibility test can be performed.
Microscopy:
Gram-positive cocci, nonmotile, tend to be arranged in tetrads or carcinae
Staphylococcus aureus

Staphylococcus aureus
Methicillin-resistant Staphylococcus aureus (MRSA) on Brilliance MRSA Chromogenic Agar. Cultivation 18 hours in an aerobic atmosphere, 35°C.
Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium responsible for several difficult-to-treat infections in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-resistant Staphylococcus aureus(ORSA). MRSA is any strain of Staphylococcus aureus that has evolved resistance to beta-lactam antibiotics, which include the penicillins (methicillin, dicloxacillin, nafcillin, oxacillin, etc.) and the cephalosporins.

Microscopy:
Gram-positive cocci, nonmotile, tend to be arranged in grape-like clusters.




Erysipelothrix rhusiopathiae

Erysipelothrix rhusiopathiae
Erysipelothrix rhusiopathiae on columbia horse blood agar. Cultivation 72 hours in an aerobic atmosphere, 37°C. Isolate from a hand of a fishmonger. Causastive organism of erysipeloid. Often found in butchers, fishmonger and abbatoir workers.
Erysipelothrix rhusiopathiae is a Gram-positive, catalase-negative, rod-shaped bacterium. Distributed worldwide, E. rhusiopathiae is primarily considered an animal pathogen, causing a disease known aserysipelas in animals (and erysipeloid in humans). Turkeys and pigs are most commonly affected, but cases have been reported in other birds, sheep, fish, and reptiles.

Microscopy:
Gram-positive rods, nonmotile




Aeromonas hydrophila

Aeromonas hydrophila
Aeromonas hydrophila on T.C.B.S agar (Thiosulfate-Citrate-Bile salts-Sucrose agar). Cultivation 24 hours in an aerobic atmosphere, 37°C. Aeromonas hydrophila isolated from blood culture from a patient with severe diarrhoea.
Aeromonas hydrophila is a heterotrophic, Gram-negative, rod shaped bacterium. This bacterium can also be found in fresh, salt, marine, estuarine, chlorinated, and un-chlorinated water. This bacterium is the most well known of the six species of Aeromonas. Aeromonas hydrophila is not as pathogenic to humans as it is to fish and amphibians. One of the diseases it can cause in humans is gastroenteritis. This disease can affect anyone, but it occurs most in young children and people who have compromised immune systems or growth problems.

Microscopy:
Gram-negative, motile rods



Neisseria meningitidis

Neisseria meningitides
Neisseria meningitidis on New York City Agar (LCAT), cultivation 24 hours , 37°C, 5% CO2. Neisseria meningitidis from a blood culture taken from a patient with meningococcal septicaemia.

Microscopy:
Gram-negative, non-motile diplococci with adjacent sides flattened (a kidney or coffee bean appearance)






Neisseria gonorrhoeae

Neisseria gonorrhoeae
Neisseria gonorrhoeae on New York City Agar (LCAT). Culture incubated for 48 hours, 37°C, 5% CO2. Isolate from conjunctival swab from a 3 day old baby.

Microscopy:
Gram-negative, non-motile diplococci with adjacent sides flattened (a coffee bean appearance)







Pseudomonas aeruginosa

Pseudomonas aeruginosa
Colonies of Pseudomonas aeruginosa and Staphylococcus aureus (yellow) on Tryptic Soy Agar. Cultivation 24 hours in an aerobic atmosphere, 37°C.
An opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa typically infects the pulmonary tract, urinary tract, burns and wounds. It is the most common cause of infections of burn injuries and of the external ear (otitis externa), and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.

Microscopy:
Gram-negative, motile rods.


Pseudomonas aeruginosa

Pseudomonas aeruginosa
Pseudomonas aeruginosa, Staphylococcus aureus (yellow) andStaphylococcus epidermidis (small, white) on sheep blood agar. Cultivation 48 hours in an aerobic atmosphere, 37°C.Beta hemolysis around colonies ofP.aeruginosa and S.aureus.
An opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa typically infects the pulmonary tract, urinary tract, burns and wounds. It is the most common cause of infections of burn injuries and of the external ear (otitis externa), and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.

Microscopy:
Gram-negative, motile rods.


Pseudomonas aeruginosa

Pseudomonas aeruginosa
Pseudomonas aeruginosa on Cetrimide Agar. Cultivation 48 hours in an aerobic atmosphere, 37°C. P. aeruginosa secretes a variety of pigments, including pyocyanin (blue-green), pyoverdine (yellow-green and fluorescent), and pyorubin (red-brown).
An opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa typically infects the pulmonary tract, urinary tract, burns and wounds. It is the most common cause of infections of burn injuries and of the external ear (otitis externa), and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.

Microscopy:
Gram-negative, motile rods.


Pseudomonas aeruginosa

Pseudomonas aeruginosa
Pseudomonas aeruginosa colonies on blood agar. Cultivation 48 hours in an aerobic atmosphere, 37°C. Small, smooth colonis of Enterococcus faecalis.
An opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa typically infects the pulmonary tract, urinary tract, burns and wounds. It is the most common cause of infections of burn injuries and of the external ear (otitis externa), and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.

Microscopy:
Gram-negative, motile rods.



Pseudomonas aeruginosa

Pseudomonas aeruginosa
Pseudomonas aeruginosa and Enterococcus faecalis colonies on Tryptic Soy Agar. Cultivation 48 hours in an aerobic atmosphere, 37°C.
An opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa typically infects the pulmonary tract, urinary tract, burns and wounds. It is the most common cause of infections of burn injuries and of the external ear (otitis externa), and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.

Microscopy:
Gram-negative, motile rods.





Pseudomonas aeruginosa

Pseudomonas aeruginosa
Pseudomonas aeruginosa and Staphylococcus aureus on Tryptic Soy Agar. Cultivation 48 hours in an aerobic atmosphere, 37°C.
An opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa typically infects the pulmonary tract, urinary tract, burns and wounds. It is the most common cause of infections of burn injuries and of the external ear (otitis externa), and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.




Beta hemolysis on blood agar

Beta hemolysis on blood agar
Beta hemolysis on sheep blood agar (beta hemolytic streptococci). Cultivation 48 hours in an aerobic atmosphere, 37°C. Skin flora.

Microscopy:
Gram-positive cocci in chains.







Gamma hemolysis on blood agar

Gamma hemolysis on blood agar
Gamma hemolysis on sheep blood agar (non-hemolytic colonies of Enterococcus faecalis). Beta hemolysis around colony of Staphylococcus aureus. Cultivation 48 hours in an aerobic atmosphere, 37°C.

Microscopy:
Gram-positive cocci in chains.






Pseudomonas aeruginosa
Pseudomonas aeruginosa
Colonies of Pseudomonas aeruginosa and Enterococcus faecalis on Tryptic Soy Agar. Cultivation 48 hours in an aerobic atmosphere, 37°C.
P.aeruginosa: oxidase: + catalase: + pigment: pyocyanin (blue- green)and pyoverdine (yellow-green, fluorescent) 
E.faecalis: oxidase: - catalase: - pigment: non-pigmented
An opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa typically infects the pulmonary tract, urinary tract, burns and wounds. It is the most common cause of infections of burn injuries and of the external ear (otitis externa), and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.

Microscopy:
Gram-negative, motile rods.

Staphylococcus aureus

Staphylococcus aureus
Staphylococcus aureus on tryptic soy agar. Cultivation 24 hours at 37°C.
Basic shape of colony: circular
Elevation: convex
Margin: entire
Pigmet production: staphyloxanthin(yellow

S. aureus is a facultatively anaerobic, Gram-positive coccus, which appears as grape-like clusters when viewed through a microscope, and has large, round, golden-yellow colonies, often with hemolysis, when grown on blood agar plates. The golden appearance is the etymological root of the bacterium's name; aureus means "golden" in Latin. 
Some strains of Staphylococcus aureus are capable of producing staphyloxanthin - a golden coloured carotenoid pigment. This pigment acts as a virulence factor, primarily by being a bacterial antioxidant which helps the microbe evade the reactive oxygen species which the host immune system uses to kill pathogens. Mutant strains of S. aureus modified to lack staphyloxanthin are less likely to survive incubation with an oxidizing chemical, such as hydrogen peroxide than pigmented strains. Mutant colonies are quickly killed when exposed to human neutrophils, while many of the pigmented colonies survive. 


Staphylococcus epidermidis

Staphylococcus epidermidis
Staphylococcus epidermidis on Tryptic Soy Agar. Cultivation 24 hours in an aerobic atmosphere, 37°C.

Microscopy:
Gram-positive cocci in clusters.





Pseudomonas aeruginosa
Staphylococcus aureus
Enterococcus faecalis

Pseudomonas aeruginosa
Staphylococcus aureus
Enterococcus faecalis
Blue-green colonies of Pseudomonas aeruginosa, white colonies of Enterococcus faecalis and yellow colonies of Staphylococcus aureus. Tryptic Soy Agar. Cultivation 24 hours in an aerobic atmosphere, 37°C.



Staphylococcus aureus
(Golden staph)

Staphylococcus aureus on Tryptic Soy Agar. Cultivation 24 hours in an aerobic atmosphere, 37°C. Staphyloxanthin production (a golden coloured carotenoid pigment).
Microscopy:
Gram-positive cocci in clusters.






Streptococcus equi ssp. equi

Streptococcus equi ssp. equi
(Group C)
Beta hemolysis on sheep blood agar. Mucous colonies, encapsulated strain. Cultivation 48 hours in an aerobic atmosphere, 37°C.








Deoxycholate Citrate Agar

Deoxycholate Citrate Agar
Lactose-negative, H2S positive colonies of Salmonella enterica on Deoxycholate Citrate Agar. Mixture of lactose-negative and lactose-positive enteric bacteria.









Pseudomonas aeruginosa

Pseudomonas aeruginosa
Pseudomonas aeruginosa on tryptic soy agar. Cultivation 24 hours at 37°C + 24 h. at room temperature.
Basic shape of colonies: circular
Elevation (cross sectional shape of the colony): raised
Margin: undulate
Pigmet production: pyocyanin (blue-green)
Compare P.aeruginosa with S.aureus (yellow colony in detail)
Basic shape of colony: circular
Elevation: convex
Margin: entire
Pigmet production: staphyloxanthin(yellow)
Pseudomonas aeruginosa is often preliminarily identified by its typical odor in vitro. It resembles (in some strains) blooming Philadelphus coronarius (Sweet Mock-orange, English Dogwood), a species of deciduous shrubs in the genus Philadelphus, native to Southern Europe.

 

Pseudomonas aeruginosa is the most common cause of infections of burn injuries and of the outer ear (otitis externa), and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.
P. aeruginosa is naturally resistant to a large range of antibiotics and may demonstrate additional resistance after unsuccessful treatment, in particular, through modification of a porin. It should usually be possible to guide treatment according to laboratory sensitivities, rather than choosing an antibiotic empirically.


















Mycobacterium vaccae

Mycobacterium vaccae
Mycobacterium vaccae is in the same genus as Mycobacterium tuberculosis, the bacterium which causes tuberculosis. Early trials indicated that exposure toMycobacterium vaccae would relieve tuberculosis symptoms. However, a 2002 review found no benefit from immunotherapy with M. vaccae in people with tuberculosis. There seems to be varying results because of two different forms of the bacterium ("smooth" and "rough"), plus individual response to vaccination from it.

Microscopy:
Acid-fast rods.





Serratia marcescens

Serratia marcescens
Why is Serratia marcescens red and white at the same time?
You will find more on the Exploring the invisible blog.

Microscopy:
Gram-negative, motile rods.






Chromobacterium violaceum 
and Erwinia carotovora

Chromobacterium violaceum and Erwinia carotovora
Chromobacterium violaceum is part of the normal flora of water and soil of tropical and sub-tropical regions of the world. It produces a natural antibiotic called violacein, which may be useful for the treatment of colon and other cancers. It grows readily on nutrient agar, producing distinctive smooth low convex colonies with a dark violet metallic sheen (due to violacein production). 
Chromobacterium violaceum produces a number of natural antibiotics. One of them is aztreonam a monobactam antibiotic that is active against gram-negative aerobic bacteria including Pseudomonas aeruginosa. It is marketed as Azactam.
Pectobacterium carotovorum (Erwinia carotovora) is a bacterium of the family Enterobacteriaceae; it formerly was a member of the genus Erwinia. The species is a plant pathogen with a diverse host range, including potato, African violet, and other agriculturally and scientifically important plant species. It causes soft rot and blackleg of potato and vegetables, as well as slime flux on many different tree species.

Microscopy:
Gram-negative coccobacilli and Gram-negative rods

Bacillus mycoides Serratia marcescens

Bacillus mycoides Serratia marcescens
Gram-positive vs Gram-negative

Battlefield on Petri dish. Serratia marcescens (red colonies) besieged by Bacillus mycoides. Serratia appears to produce an anitibiotic that protects it from the invading Bacillus strain.

Microscopy:
Bacillus spp.
Gram-positive, spore-forming rods.
Serratia spp.
Gram-negative rods




Bacillus mycoides

Bacillus mycoides
Typical appearance of Bacillus mycoides. A very common bacterial inhabitant of soil which has a unique mechanism of movement.
Ubiquitous in nature, Bacillus includes both free-living and pathogenic species. Under stressful environmental conditions, the cells produce oval endospores that can stay dormant for extended periods. These characteristics originally defined the genus, but not all such species are closely related, and many have been moved to other genera. 

Microscopy:
Gram-positive, spore-forming rods.





Alpha hemolysis

Alpha hemolysis
Alpha hemolysis on sheep blood agar. Cultivation 48 hours in an aerobic atmosphere, 37°C. Skin flora.











Beta hemolysis

Beta hemolysis
Beta hemolysis on sheep blood agar. Beta hemolytic streptococci. Cultivation 48 hours in an aerobic atmosphere, 37°C. Skin flora.











Beta hemolysis

Beta hemolysis
Beta hemolysis of S.aureus on sheep blood agar. Cultivation 48 hours in an aerobic atmosphere, 37°C.











Mannitol Salt Agar

Mannitol Salt Agar
Staphylococcus aureus and Staphylococcus epidermidis on Mannitol Salt Agar. Cultivation 24 hours in an aerobic atmosphere, 37°C. Yellow, mannitol positive Staphylococcus aureus with yellowish halo around colonies. Whittish, mannitol negative colonies of Staphylococcus epidermidis.










Proteus mirabilis

Proteus mirabilis
Proteus mirabilis on blood agar. Cultivation 24 hours in an aerobic atmosphere, 37°C. The generaProteus is named after a Greek polymorphic sea god and for most strains of P.mirabilis and P.vulgarisis typical their ability to swarm over the surfaces of solid cultivation media (the spreading growth covers other organisms in the culture and thus delays their isolation).









viridans streptococci

viridans streptococci
Colonies of viridans streptococci on blood agar surroundend by a wide zone of alpha-hemolysis. Cultivation 24 hours in an aerobic atmosphere enriched with 5% carbon dioxide, 37°C.
Viridans Streptococcus is a pseudotaxonomic non-Linnaenan term for a large group of commensal streptococcal bacteria that are either alpha-hemolytic, producing a green coloration on blood agar plates (hence the name "viridans", from Latin "viridis", green), or nonhemolytic. They possess no Lancefield antigens. 
In general, pathogenicity is low. The organisms are most abundant in the mouth, and one member of the group, S. mutans, is the etiologic agent of dental caries. Others may be involved in other mouth or gingival infections. If they are introduced into the bloodstream, they have the potential of causingendocarditis, particularly in individuals with damaged heart valves. They are the most common causes of subacute bacterial endocarditis. Viridans streptococci have the unique ability to synthesize dextrans from glucose, which allows them to adhere to fibrin-platelet aggregates at damaged heart valves. This mechanism underlies their ability to cause subacute valvular heart disease following their introduction into the bloodstream (e.g., following tooth extraction).

Microscopy:
Gram-positive, non-motile cocci.
Pseudomonas aeruginosa

Pseudomonas aeruginosa
Colonies of Pseudomonas aeruginosa on blood agar surroundend by a wide zone of beta-hemolysis. Cultivation 48 hours in an aerobic atmosphere, 37°C.
An opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa typically infects the pulmonary tract, urinary tract, burns and wounds. It is the most common cause of infections of burn injuries and of the external ear (otitis externa), and is the most frequent colonizer of medical devices (e.g., catheters). Pseudomonas can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias, being one of the most common agents isolated in several studies.

Microscopy:
Gram-negative, motile rods.



Proteus mirabilis

Proteus mirabilis
Proteus mirabilis on blood agar. Characteristic swarming motility. Cultivation 24 hours in an aerobic atmosphere, 37°C.
This rod shaped bacterium has the ability to produce high levels of urease. Urease hydrolyzes urea to ammonia (NH3) and thus makes the urine more alkaline. If left untreated, the increased alkalinity can lead to the formation of crystals of struvite, calcium carbonate, and/or apatite. The bacteria can be found throughout the stones, and these bacteria lurking in the stones can reinitiate infection after antibiotic treatment. Once the stones develop, over time they may grow large enough to cause obstruction and renal failure. Proteus can also cause wound infections, septicemia and pneumonias, mostly in hospitalized patients.

Microscopy:
Gram-negative, motile rods.





Bacteria
A few examples of bacteria isolated from clinical material.


















Streptomyces spp.

Streptomyces spp.
Streptomyces spp. on various cultivation media. Production of different pigments and formation of aerial mycelia. Colonies after approximately 15 days of cultivation in aerobic atmosphere, 28°C.
Streptomycetes are characterised by a complex secondary metabolism. Theyproduce over two-thirds of the clinically useful antibiotics of natural origin. The now uncommonly-used streptomycin (the first antibiotic effective against tuberculosis; S.A.Waksman,1952, The Nobel Prize in Physiology/Medicine) takes its name directly from Streptomyces. 

Members of the Streptomyces genus are the source for innumerable other antibacterial pharmaceutical agents; among the most important of these are:
Cefoxitin
S. lactamdurans
Neomycin
S. fradiae
Chloramphenicol
S. venezuelae
Puromycin
S. alboniger
Daptomycin
S. roseosporus
Rifamycin
S. mediterranei
Fosfomycin
S. fradiae
Tetracycline
S. rimosus
Lincomycin
S. lincolnensis
Vancomycin
S. orientalis
Thanks to clavulanic acid (from S. clavuligerus) are antibiotics like amoxicillin (amoxicillin/clavulanate=Augmentin) or ticarcillin (ticarcillin/ clavulanate=Timentin) still very useful in treatment of many bacterial infections.

Microscopy:
Gram-positive, non-motile, rod-shaped bactera. Produce spores.
































"Streptomyces coelicolor" A3(2)
Streptomyces violaceoruber

"Streptomyces coelicolor" A3(2)
Streptomyces violaceoruber
Colony of "Streptomyces coelicolor" A3(2) on Mueller-Hinton agar. Cultivation 25 days, 28°C. Colony is completely covered with aerial mycelium with spores. The bacterium produces antibiotic actinorhodin (deep blue pigment colouring surrounding cultivation medium). Production of actinorhodin takes place when cultures of S. coelicolor A3(2) enter the stationary phase.
Aerial mycelia are the forerunners of hyphal spores and differ from the substrate mycelia physiologically as well as by being considerably more hydrophobic. The formation of the spores and aerial mycelia give a colony of Streptomyces itscharacteristic fuzzy, powdery appearance.

Microscopy:
Gram-positive, non-motile, rod-shaped bacterium. Produces spores.

Bacillus sp.

Bacillus sp.


Bacillus sp. on Mueller-Hinton agar. Cultivation in aerobic atmosphere, 28°C, 48 hours. Environmental isolate.
Streptomycetes and related genera are not the only bacteria producing clinicaly useful antibiotics. Some species from genus Bacillus produce, for example: 

Colistin (polymyxin E) (Bacillus polymyxa var. colistinus). It is one of the last-resort antibiotics for multidrug-resistant Pseudomonas aeruginosa andAcinetobacter. New Delhi metallo-ß-Lactamase multidrug-resistantEnterobacteriaceae have also shown susceptibility to colistin. 

Bacitracin (Bacillus subtilis var. Tracy): a common ingredient of eye and skin antibiotic preparations (in the United States, the popular brand name Neosporin: bacitracin along with neomycin and polymyxin B (derived from Bacillus polymyxa).


Microscopy:
Gram-positive, rod-shaped bactera. Produce endospores.
Bacteria isolated from soil

Bacteria isolated from soil
Mixture of soil bacteria on agar plate (M2 medium with cycloheximide for inhibition of soil fungi). Cultivation 5 days, 28°C. Soil sample was treated with 1.5 M NaOH so predominant colonies belong toBacillus spp.(and related aerobic, endospore-forming genera), Mycobacterium spp. and other spore-forming Actinobacteria.
Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste, water, and deep in the Earth's crust, as well as in organic matter and the live bodies of plants and animals. There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water; in all, there are approximately five nonillion (5×1030) bacteria on Earth, forming a biomass on Earth, which exceeds that of all plants and animals. However, most bacteria have not been characterised, and only about half of the phyla of bacteria have species that can be grown in the laboratory.
There are approximately ten times as many bacterial cells in the human flora as there are human cells in the body, with large numbers of bacteria on the skin and as gut flora. The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, and a few are beneficial.

Microscopy:
Various Gram-positive, spore-forming bacteria and acid-fast mycobacteria.
Streptomyces sp.

Streptomyces sp.
Streptomyces sp. on YEME agar. Cultivation 20 days, 28°C. Colonies are completely covered with whitish aerial mycelium and cultivation medium is colored with brown diffusible pigment. This strain produces some manumycin-type antibiotics.

Microscopy:
Gram-positive, non-motile, rod-shaped bactera. Produce exospores.