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28 Cards in this Set
- Front
- Back
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What are some of the basic characteristics of anaerobic bacteria
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Can't use O2 as a final electron acceptor; Unable to break down H2O2 because they lack catalase; Toxic superoxide anions accumulate in the presence of O2
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What is the definition of botulism
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A life threatening, paralytic illness produced by neurotoxins elaborated by C. botulinum. Occurs with food poisoning, wounds, and infancy
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What are some basic characteristics of Botulinum toxin
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Released during growth and autolysis of bacteria. Seven types identified, though A, B, and E most commonly produce disease in humans. Most potent poisons known. Toxin can be destroyed by heat, but spores are heat resistant
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What is the mode of action of botulinum toxin
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Interferes with release of the neurotransmitter acetylcholine, causing flaccid paralysis
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What is the pathogenesis of Botulism food poisoning
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Foods at alkaline pH are eaten without cooking. Toxin is absorbed from the stomach and small bowel. Pancreatic trypsin enhances toxicity of type E
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What is the pathogenesis of Infant botulism
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Infant tract is colonized with C. botulinum from an unknown source (possibly honey); toxin production occurs in vivo
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What is the epidemiology of Clostridium botulinum
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Ubiquitous in soil. Most often acquired from home-canned or prepared foods
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What are the clinical manifestations of food-borne botulism
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Symptoms 12-36hrs after ingestion; Double vision, dry mouth, descending paralysis; no fever, type E produces food poisoning; High mortality rate, those who recover do not develop antitoxin
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How is botulism treated
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Administration of antitoxin prepared in horses; Adequate ventilation; ventilator if diaphragm is paralyzed
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What is the definition of Tetanus
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Produced by action of neurotoxin tetanospasmin which is elaborated during the growth of Clostridium tetani. Frequently fatal, but prevented by immunization
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What are the characteristics of Clostridium tetanus and its toxin
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Gram positive anaerobic rod; one antigenic type of toxin that is produced by vegetative cells and released by lysis; one of the most potent toxins in the world
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What is the mode of action of tetanus toxin
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Cleaves VAMP and prevents release of neurotransmitter glycine from inhibitor interneurons in the spinal cord
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What is the pathogenesis of tetanus
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Introduced by wounds, cuts, or burns; converts to vegetative form; disseminated through the blood stream; combines avidly with gangliosides
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What is the epidemiology of Clostridium tetani
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Found worldwide in soil; affects the unimmunized or inadequately immunized
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What are the clinical manifestations of tetanus
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Variable incubation period, from a few days to 3 weeks; more severe at either extreme of life; can be local or generalized
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What are the characteristics of generalized tetanus
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Lockjaw and risus sardonicus; Stiffness of the neck, difficulty in swallowing, rigidity of ab muscles; tonic spasms; respiratory difficulty
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How is tetanus primarily diagnosed
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Clinical picture and history of injury
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How is tetanus treated
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Antitoxin (doesn't neutralize toxin already bound to nerve tissue); muscle relaxants, sedation, assisted ventilation; Meticulous clinical management is crucial
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How is tetanus prevented
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Immunization; proper wound care; prophylactic use of antitoxin; administration of penicillin
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What bacteria is the most common cause of invasive clostridial infections
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Clostridia perfringens
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What are the characteristics of Clostridia perfringens
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Gram positive rod, aerotolerant, stormy fermentation in milk
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What are the toxins of Clostridium perfringens
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Many toxins that are active in tissue plus an enterotoxin. The alpha toxin is a lecithinase that is hemolytic, destroys platelets, and causes widespread damage
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What intestinal disorder does Clostridium perfringens produce
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Food poisoning from cooked beef. Large numbers of vegetative cells are ingested and sporulate in the gut, where an enterotoxin is produced. Incubation period is 6-18 hrs
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What is pseudomembraneous enterocolitis
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Severe, necrotizing process involving the large intestine which occurs as a complication of antibiotic therapy. Includes clindamycin, ampicillin and amoxicillin, and cephlosporins
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What disease is Clostridium difficile implicated in
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Pseudomembranous enterocolitis. It overgrows drug-sensitive normal gut flora organisms. Produces enterotoxin A and necrotizing cytoxin B (depolymerizes actin)
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What is the preeminent anaerobic pathogen in humans
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Bacteroides fragilis. It has a strong penchant for producing abcesses and causing tissue destruction
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What are the characteristics of Bacteroides fragilis
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Aerotolerant anaerobe, no spores, non motile, gram negative. Normal flora of upper respiratory, intestinal, and female genital tracts. Polysaccharide capsule is the virulence factor
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Mixtures of anaerobes (such as Gram positive Peptostreptococcus, Actinomyces, and Gram negative Prevotella, Prophyromonas, and Fusobacterium nucleatum) with Bacteroides fragilis can cause what
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Polymicrobial infections such as peridontitis and pelvic inflammatory disease
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