Microbiology and Immunology

Microbiology, clinical WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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corkscrew movement (courtesy of rigid internal filaments that

run the length of the bacterium). A related group (a genus) of

spiral shaped bacteria is Spirilla.These bacteria move by

means of external flagella, not by means of the internal fila-

ments. Two members of Spirillaare important disease-causing

bacteria. The first is Campylobacter jejuni, which frequently

contaminates raw meat such as poultry and drinking water,

and which is the cause of diarrhea, especially in children. The

second bacterial type is Helicobacter pylori, which grows in

the stomach and has been demonstrated to be the principle

cause of stomach ulcers.

Another group of clinically relevant bacteria is termed

pseudomonads. This group contains many different types of

bacteria. They all are similar in shape and biochemical behav-

ior to a species called Pseudomonas aeruginosa. Most

pseudomonads, like Pseudomonas aeruginosalive in water

and the soil. They cause a variety of ailments. Bordetella per-

tussis causes whooping cough, Legionella pneumophila

causes Legionnaires’ disease, Neisseria gonorrhoeaecauses

gonorrhea, and Neisseria meningitidescauses bacterial menin-

gitis. Pseudomonas aeruginosais the quintessential so-called

opportunitistic pathogen; a bacteria that does not normally

cause an infection but can do so in a compromised host.

Examples of such infections are the chronic lung infections in

those who have certain forms of cystic fibrosis, and infections

in burn victims.

Yet another group of bacteria of medical importance

live in the intestinal tracts of humans, other mammals and

even in birds and reptiles. These are the enteric bacteria. The

best-known enteric bacteria is Escherichia coli, the cause of

intestinal illness and sometimes even more severe damage to

the urinary tract and kidneys from ingestion of contaminated

water or food (“hamburger disease”). Other noteworthy

enteric bacteria are Shigella dysenteriae (dysentery),

Salmonella species gastroenteritis and typhoid fever),

Yersinia pestis (bubonic plague), and Vibrio cholerae

(cholera).

Bacteria including Staphylococcusand Streptococcus,

which normally live on the skin, can cause infection when

they gain entry to other pasts of the body. The illnesses they

cause (such as strep throat, pneumonia, and blood infection,

as examples), and the number of cases of these illnesses, make

them the most clinically important disease-causing bacteria

known to man. Staphylococcus aureusis the leading cause of

hospital acquired infections of all the gram-positive bacteria.

Ominously, a strain of this organism now exists that is resist-

Laboratory technicians.

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