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Clostridium Gram-Positive Rods Spore-forming gram positive rods Bacillus Clostridium Bacillus There are two medically important Bacillus species: Bacillus anthracis and Bacillus cereus.
1. Bacillus anthracis Important Properties: Bacillus anthracis is Aerobica, large gram-positive rod with square ends, frequently found in chains, its antiphagocytic capsule is composed of D- glutamate. It is non-motile Habitat and Transmission— Habitat is soil. Transmission is by contact with infected animals or inhalation of spores from animal hair and wool. Disease: Bacillus anthracis causes anthrax, which is common in animals but rare in humans. Pathogenesis is based primarily on the production of two exotoxins, collectively known as anthrax toxin. Human disease occurs in three main forms: cutaneous, pulmonary (inhalation), and gastrointestinal. 1) Cutaneous anthrax: is a painless ulcer with a black eschar. Untreated cases progress to bacteremia and death. 2) Pulmonary (inhalation) anthrax: begins with nonspecific respiratory tract symptoms resembling influenza, especially a dry cough, this rapidly progresses to hemorrhagic septic shock, and death. 3) Gastrointestinal anthrax, the symptoms include vomiting, abdominal pain, and bloody diarrhea. Treatment: C iprofloxacin is the drug of choice. Doxycycline is an alternative drug. Dr. Yusor AL-Asadi
Clostridium
2. Bacillus cereus : Disease: Bacillus cereus causes food poisoning Important Properties: Aerobic, gram-positive, spore-forming rod. Transmission: Spores on grains such as rice survive steaming and rapid frying. The spores germinate when rice is kept warm for many hours (e.g., reheated fried rice). The portal of entry is the gastrointestinal tract. Bacillus cereus produces two enterotoxins and There are two syndromes: (1) One syndrome has a short incubation period (4 hours) and consists primarily of nausea and vomiting, similar to staphylococcal food poisoning. (2) The other has a long incubation period (18 hours) and features watery, non-bloody diarrhea. Clostridium : There are four medically important species: Clostridium tetani , Clostridium botulinum , Clostridium perfringens (which causes either gas gangrene or food poisoning), and Clostridium difficile. All clostridia are anaerobic spore- forming, gram-positive rods 1. Clostridium tetani Disease: Clostridium tetani causes tetanus Characteristics: Anaerobic, gram-positive, spore-forming rods. Spore is at one end (“terminal spore”), so organism looks like a tennis racket. Transmission: Spores are widespread in soil; Organism enters through traumatic breaks in the skin.
Clostridium Neurological signs and symptoms, the toxin carried via the blood to peripheral nerve synapses, where it blocks release of acetylcholine causing flaccid paralysis.
4. Clostridium perfringens Characteristics: Anaerobic, gram-positive, spore-forming rods. Habitat and Transmission: Habitat is soil and human colon. Depending on the route of entry into the body, Clostridium perfringens causes two distinct diseases: 1 - gas gangrene. 2 - food poisoning. 1 - Gas gangrene (myonecrosis, necrotizing fasciitis) is one of the two diseases caused by C. perfringens Pathogenesis: I. Gas gangrene in wounds is caused by germination of spores under anaerobic conditions II. production of several cytotoxic factors, especially alpha toxin, a lecithinase that cleaves cell membranes including those of erythrocytes resulting in hemolysis. III. Degradative enzymes produce gas in tissues. Gas in tissue (CO2 and H2). IV. Clinical Findings Pain, edema, cellulitis, and gangrene (necrosis) Shock and death can ensue. Mortality rates are high. Treatment: Penicillin G is the antibiotic of choice. Food Poisoning : Food poisoning is the second disease caused by C. perfringens. Transmission: Spores are located in soil and can contaminate food. The heat- resistant spores survive cooking and germinate
Clostridium Pathogenesis: Clostridium perfringens is a member of the normal flora in the colon but not in the small bowel, where the enterotoxin within the gut acts as a superantigen, similar to that of cause diarrhea with cramps and little vomiting, it resolves in 24 hours. Treatment: Symptomatic treatment is given; no antimicrobial drugs are administered.
5. Clostridium difficile Disease: Clostridium difficile causes antibiotic-associated pseudomembranous colitis Characteristics: Anaerobic, gram-positive, spore-forming rods Transmission: The organism colonizes the large intestine, note that most people are not colonized, which explains why most people who take antibiotics do not get pseudomembranous colitis Pathogenesis: Antibiotics suppress drug-sensitive members of the normal flora of the colon, allowing C. difficile to multiply and produce exotoxins A and B. Clostridium difficile causes diarrhea associated with pseudomembranes (yellow-white plaques) on the colonic mucosa, the diarrhea is usually not bloody, Fever and abdominal pain often occur. Treatment: Oral metronidazole or vancomycin should be given and fluids replaced.
