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Clinical Microbiology
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Gram Positive Cocci

Enterococcus page

Enterococcus sp and Enterococcus faecalis on next page.

Streptococcus pneumoniae
Strep pneumo

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Strep sanguis
Strep sanguis

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Streptococcus imitis
Strep mitis

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Strep B
Strep B

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Staphylococcus aureus

Staphylococcus aureus
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Staphylococcus epidermidis

Staphylococcus epidermidis
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Staph MR

Staph MR

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Gram-positive cocci
Everyone has heard the trivial terms, "staph and strep germs." Use of the term, "germ," is a way of trivializing the idea of an infectious biological agent for children. We aren't quite sure why that sort of trivialization is continued into adulthood. Click for ideas on teaching bacteriology.

Staphylococcus aureus . Staphylococcus is a very well known genus of bacteria. Colonies are "gold," or yellow on sheep blood agar solid media, hence the name. A common pathogen, boils, acne, wound infections, food poisoning are among a host of conditions caused by this organism. The organism is both pathogenic and invasive. It produces leukotoxin which can kill white blood cells and a wide variety of other toxins. S. aureus is quite pyogenic and in decades past was named Staphylococcus pyogenes, however that specific name is currently applied to one GPC, Streptococcus pyogenes.


S. aureus

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Increasingly, and especially in hospital, strains of both S. aureus and S. epidermidis have become resistant to the antibiotic DOC, methicillin. Such strains have been labelled Staph MR. Other clinically significant species include, S. haemolyticus, S. hominis and S. saprophyticus.

Staph MR

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Staphylococcus sp. (Coagulase-negative) Staphylococcus epidermidis, appears as white colonies on sheep blood agar plates. While both S aureus and S epidermidis are normal inhabitants of the skin, epidermidis had been considered the lesser of the two in virulence. Most S aureus strains test positive for coagulase, clot formation in tube of citrated rabbit plasma. The other species test negative. "Infections by S. epidermidis, S. haemolyticus, and S. hominis, are associated with intravascular devices (prosthetic heart valves and intra-arterial or intravenous lines) and shunts. Also quite common are infections of prosthetic joints, wound infections, osteomyelitis associated with foreign bodies, and endocarditis." Dr GE Kaiser
cat.cc.md.us/courses/bio141/labmanua/lab15/l15index.html

Staph epi
S. epidermidis

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Micrococcus sp. is a contaminant virtually every time. One definite exception is when it arrives in hospital accreditation test samples in which it is a "freebie." So it deserves mention. If you have ever looked at it under the microscope, you might wonder about the Micro- part of the name, since on gram stain, the cocci can be quite large. Pairs and clusters are seen. Catalase positive. Growth on mannitol agar. What else. "Three common species of Micrococcus are M. luteus, M. roseus, and M. varians."
Micrococcus information, medic.med.uth.tmc.edu/path/00001448.htm
View a gram stain, such as it is, M. luteus, buckman.com/eng/micro101/2256.htm
Family Streptococcaceae
"Streptococcus, plural streptococci, any member of a genus (Streptococcus) of spheroidal bacteria in the family Streptococcaceae. The term streptococcus ("twisted berry") refers to the bacteria's characteristic grouping in chains resembling a string of beads." "Streptococci can also be classified by the type of carbohydrate contained in the cell wall, a system called the Lancefield classification." Encyclopedia Britannica Agglutination and immunofluorescent antibody microscopic methods can quickly identify Lancefield groups.
Streptococcus pyogenes
Streptococcus pyogenes electron micrographs, Rockefeller University, A downloadable set of eleven electron micrographs of Streptococcus pyogenes of exceptional quality.Click link or thumbnail: rockefeller.edu/vaf/ems.htm

Lancefield Group A, S. pyogenes species of streptococci cause rheumatic fever, scarlet fever, erysipelas, strep throat, tonsillitis, and other upper respiratory infections. In case you are wondering which streptococcal species is the worst, Streptococcus pyogenes, Lancefield group A is the bad boy in the Strep family. It is so important that physicians don't want any silly mistakes with names. "Pyogenes? What's that?" Physicians are programmed to react to the term "Strep group A."
A recently sensationalized strain of an especially invasive Lancefield group A Streptococcus carries the terms "pyo-," pus. "-gen-," forming. "necrotizing fascitis," flesh eating, to a very rare extreme. Once established under the skin, a focus of infection can spread liquifying flesh as it moves outwardly at a rate as rapid as one inch per hour. Sounds scary. You have five times more probability of getting hit by lightning.
In common practice Streptococcus group A is usually found in samples from the throat, nasopharanyx, or in sputum in which a plethora of unimportant normal flora is also present. Its characteristic type of hemolysis is key for detection. If there is an area of clear or "beta," hemolysis, the possibility of the presence of group A organisms exists, although the same type of hemolysis pattern may also be exhibited by some other organisms such as some gram negative rods which may also be present. The bacterial colony is carefully scooped up, placed on a glass slide and mixed with a fluorescent antibody. If the organisms fluoresce when examined by fluorescent microscope, the presence of Streptococcus group A is confirmed. In laboratories which lack the relatively high tech fluorescent microscopes, the colonies are replated and streaked for isolation and identified with older methods. In these cases an extra incubation period, (day) is required.
Streptococcus pneumoniae is a member of the Viridans group, so called because of green or, "alpha," hemolysis on sheep blood agar, causes lower respiratory infection pneumonia and upper respiratory infections bronchitis, laryngitis, otitis media (middle ear) and sinusitis.
The encapsulated, gram-positive coccoid bacteria have a distinctive morphology on gram stain, the so-called, "lancet shape," which actually looks more like a blunt arrow head.


Streptococcus pneumoniae, in blood culture.
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Streptococcus and Bacillus sp.

Streptococcus pneumoniae, Bacillus sp., SEM x48,000


Streptococcus pneumonaie in bacterial meningitis:
"Before the 1990s, Haemophilus influenzae type b (Hib) was the leading cause of bacterial meningitis, but new vaccines being given to all children as part of their routine immunizations have reduced the occurrence of invasive disease due to H. influenzae. Today, Streptococcus pneumoniae and Neisseria meningitidis are the leading causes of bacterial meningitis."
"High fever, headache, and stiff neck are common symptoms of meningitis in anyone over the age of 2 years.""The diagnosis is usually made by growing bacteria from a sample of spinal fluid. The spinal fluid is obtained by performing a spinal tap, in which a needle is inserted into an area in the lower back where fluid in the spinal canal is readily accessible. Identification of the type of bacteria responsible is important for selection of correct antibiotics."
cdc.gov/ncidod/dbmd/diseaseinfo/meningococcal_g.htm
Streptococcus agalactiae, group B

Streptococcus agalactiae, Lancefield group B, in blood culture.

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"GBS is the most common cause of sepsis (blood infection) and meningitis (infection of the fluid and lining surrounding the brain) in newborns. GBS is a frequent cause of newborn pneumonia and is more common than other, better known, newborn problems such as rubella, congenital syphilis, and spina bifida. Before prevention methods were widely used, approximately 8,000 babies in the United States would get GBS disease each year. One of every 20 babies with GBS disease dies from infection. Babies that survive, particularly those who have meningitis, may have long-term problems, such as hearing or vision loss or learning disabilities.""Approximately one of every 100 to 200 babies whose mothers carry GBS develop signs and symptoms of GBS disease."" In pregnant women, GBS can cause bladder infections, womb infections (amnionitis, endometritis), and stillbirth. Among men and among women who are not pregnant, the most common diseases caused by GBS are blood infections, skin or soft tissue infections, and pneumonia. Approximately 20% of men and nonpregnant women with GBS disease die of the disease."

"Many people carry GBS in their bodies but do not become ill. These people are considered to be "carriers." Adults can carry GBS in the bowel, vagina, bladder, or throat. People who carry GBS typically do so temporarily -- that is, they do not become lifelong carriers of the bacteria."

"GBS disease is diagnosed when the bacterium is grown from cultures of sterile body fluids, such as blood or spinal fluid. Cultures take a few days to complete. GBS infections in both newborns and adults are usually treated with antibiotics (e.g., penicillin or ampicillin) given through a vein."

cdc.gov/ncidod/dbmd/diseaseinfo/groupbstrep_g.htm

"Group B streptococcus (GBS) is a type of bacterium that causes illness in newborn babies, pregnant women, the elderly, and adults with other illnesses such as diabetes or liver disease. GBS is the most common cause of life-threatening infections in newborns."

Group B Streptococcus website:
cdc.gov/ncidod/dbmd/gbs/index.htm

Streptococcus mutans , Normal mouth flora. Is responsible for cavities. A vaccine is thought possible for Streptococcus mutans for the prevention of cavities.
Peptostreptococcus sp. is anaerobic. It is sometimes opportunistically involved in the infection of wounds.
Terms you may want to search:
bacteremia, bacteria in the bloodstream.
endocarditis, endo- inside. -card- heart. -itis, inflammation.
nosocomial, in hospital.
rheumatic fever, scarlet fever, erysipelas, strep throat, tonsillitis

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