Bacteriology Quiz: Bacillus anthracis and Clostridium

Bacillus Anthracis and Anthrax Disease

• Herbivorous animals are highly susceptible to anthrax disease
• Medusa-head colonies with a ground-like appearance
• Resistant to 5% phenol or mercuric chloride
• Sterne vaccine is used to prevent anthrax
• Sensitive to penicillin, lacks motility, and sensitive to gamma bacteriophage B.piliformis
• Tyzzer’s disease in lab rodents is caused by B. piliformis

Clostridium Species

• Motile and can be stained with Giemsa stain or silver impregnation
• Sensitive to penicillin
• Clostridium spiroforme has a curved or spiral form

Invasive or Enterotoxigenic Clostridia

• C. perfringens: causes lamb dysentery, struck, and pulpy kidney disease in sheep
• C. haemolyticum: causes bacterial icterohemoglobinuria or redwater disease in cattle
• C. novyi: causes black disease in sheep
• C. chauvoei: causes blackleg in cattle and sheep
• C. colinum: causes ulcerative enteritis or quail disease
• C. spiroforme: causes spontaneous and antibiotic-induced enterotoxemia in rabbits
• C. villorum: causes subcutaneous abscess in cats
• C. difficile: causes antibiotic-induced enterocolitis in hamsters

Toxin-Forming, Noninvasive Group

• C. tetani: causes tetanus, characterized by anaerobic spore-bearing bacilli
• Colonies are fluffy, cottony spheres
• Produces 3 toxins: tetanospasmin (neurotoxin), hemolysin, and a peripherally active nonspasmogenic toxin
• Tetanospasmin prevents the release of glycine
• Drumstick in appearance
• Sensitive to penicillin, resistant to aminoglycosides

C. botulinum

• Causes botulism, characterized by flaccid paralysis and eventual death due to respiratory failure
• Nonproteolytic types acidify but do not coagulate milk
• Proteolytic types slowly curdle milk, partially digest and darken the curd
• Lamziekte or lame disease arises from ingestion of contaminated food with preformed toxin
• Aphosphorosis may cause cattle and sheep to develop a depraved appetite for decaying carcasses, leading to botulism

The Tissue-Invading and Enterotoxigenic Group

• C. perfringens: from a decomposing human cadaver in which the tissues were gaseous
• Bacillus aerogenes capsulatus is widespread in soil and found in the alimentary tract in tissues of bloating cadavers of animals
• Rapidly liquefies gelatin but not coagulated egg medium or Loeffler’s blood serum
• Toxins are identified by serum-neutralization tests in mice and guinea pigs

C. haemolyticum

• Colonies grown in deep agar are lenticular at first and later become wooly
• Predilection for alkaline water and associated with pastures that contain swampy areas
• The most characteristic lesion is the large infarct that is always found in the liver
• Alum-precipitated formalinized whole cultures are used for immunization of cattle

C. novyi

• C. novyi type C is not toxigenic or pathogenic for animals
• One of the largest of anaerobic bacilli
• Requires cysteine in its reduced form
• Growth is poor in broth, but good in cooked-meat medium
• Found in the soil and in the intestinal tract of herbivorous animals
• Causes gas gangrene and black disease (necrotic hepatitis) of cattle

C. chauvoei

• Causes blackleg in ruminants
• Blackquarter, quarter evil, and symptomatic anthrax in cattle
• Causative agent of parturient gas gangrene in sheep
• Grows well on liver-brain medium
• Cattle are susceptible between 6 months and 2 years
• Entry is by the oral route during grazing
• Fluorescent antibody technique is used
• Penicillin is effective in treating blackleg if administered systemically and locally into the lesion

C. septicum

• Malignant edema bacillus and causes malignant edema in animals
• Colonies are grown in deep agar and are usually cottony and filamentous
• Produces 4 toxins: alpha, beta, gamma, and delta
• Guinea pigs are very susceptible