Gram-Positive Toxigenic Rods

Chapter 10

Gram-Positive Toxigenic Rods

Bacillus Species

• Bacilli are large, gram-positive, aerobic, spore-forming rods that produce exotoxins.

Bacillus anthracis

• B. anthracis is nonmotile (unlike other bacilli) and forms Medusa’s head colonies on blood agar.

1. Pathogenesis

2. Diseases caused by B. anthracis

• Anthrax is an occupational disease of individuals who handle wools, furs, and hides.

3. Prevention and treatment

Bacillus cereus

• B. cereus, a ubiquitous soil organism found in grains, vegetables, and dairy products, is the most common pathogenic bacilli.

1. B. cereus food poisoning

2. Prevention and treatment

Bacillus subtilis and other Bacillus species

II Clostridium Species

• Four clostridial species are important human pathogens: C. botulinum, C. difficile, C. perfringens, and C. tetani.

• Clostridia are gram-positive, anaerobic (or aerotolerant), spore-forming rods that produce potent exotoxins.

C. perfringens

• C. perfringens is found worldwide in soil, water, and sewage; normal inhabitant of the GI tract.

1. Identification

2. Pathogenesis

• Type A C. perfringens is most virulent in humans.

a. Alpha toxin (phospholipase C and lecithinase), produced by all types, causes lysis of blood cells and endothelial cells, leading to increased vascular permeability, hemolysis, and tissue destruction.

b. Hyaluronidase, collagenase, and other degradative enzymes cause tissue destruction.

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Jun 18, 2016 | Posted by in IMMUNOLOGY | Comments Off on Gram-Positive Toxigenic Rods

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