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28 Cards in this Set

  • Front
  • Back
What are some of the basic characteristics of anaerobic bacteria
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
What is the definition of botulism
A life threatening, paralytic illness produced by neurotoxins elaborated by C. botulinum. Occurs with food poisoning, wounds, and infancy
What are some basic characteristics of Botulinum toxin
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
What is the mode of action of botulinum toxin
Interferes with release of the neurotransmitter acetylcholine, causing flaccid paralysis
What is the pathogenesis of Botulism food poisoning
Foods at alkaline pH are eaten without cooking. Toxin is absorbed from the stomach and small bowel. Pancreatic trypsin enhances toxicity of type E
What is the pathogenesis of Infant botulism
Infant tract is colonized with C. botulinum from an unknown source (possibly honey); toxin production occurs in vivo
What is the epidemiology of Clostridium botulinum
Ubiquitous in soil. Most often acquired from home-canned or prepared foods
What are the clinical manifestations of food-borne botulism
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
How is botulism treated
Administration of antitoxin prepared in horses; Adequate ventilation; ventilator if diaphragm is paralyzed
What is the definition of Tetanus
Produced by action of neurotoxin tetanospasmin which is elaborated during the growth of Clostridium tetani. Frequently fatal, but prevented by immunization
What are the characteristics of Clostridium tetanus and its toxin
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
What is the mode of action of tetanus toxin
Cleaves VAMP and prevents release of neurotransmitter glycine from inhibitor interneurons in the spinal cord
What is the pathogenesis of tetanus
Introduced by wounds, cuts, or burns; converts to vegetative form; disseminated through the blood stream; combines avidly with gangliosides
What is the epidemiology of Clostridium tetani
Found worldwide in soil; affects the unimmunized or inadequately immunized
What are the clinical manifestations of tetanus
Variable incubation period, from a few days to 3 weeks; more severe at either extreme of life; can be local or generalized
What are the characteristics of generalized tetanus
Lockjaw and risus sardonicus; Stiffness of the neck, difficulty in swallowing, rigidity of ab muscles; tonic spasms; respiratory difficulty
How is tetanus primarily diagnosed
Clinical picture and history of injury
How is tetanus treated
Antitoxin (doesn't neutralize toxin already bound to nerve tissue); muscle relaxants, sedation, assisted ventilation; Meticulous clinical management is crucial
How is tetanus prevented
Immunization; proper wound care; prophylactic use of antitoxin; administration of penicillin
What bacteria is the most common cause of invasive clostridial infections
Clostridia perfringens
What are the characteristics of Clostridia perfringens
Gram positive rod, aerotolerant, stormy fermentation in milk
What are the toxins of Clostridium perfringens
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
What intestinal disorder does Clostridium perfringens produce
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
What is pseudomembraneous enterocolitis
Severe, necrotizing process involving the large intestine which occurs as a complication of antibiotic therapy. Includes clindamycin, ampicillin and amoxicillin, and cephlosporins
What disease is Clostridium difficile implicated in
Pseudomembranous enterocolitis. It overgrows drug-sensitive normal gut flora organisms. Produces enterotoxin A and necrotizing cytoxin B (depolymerizes actin)
What is the preeminent anaerobic pathogen in humans
Bacteroides fragilis. It has a strong penchant for producing abcesses and causing tissue destruction
What are the characteristics of Bacteroides fragilis
Aerotolerant anaerobe, no spores, non motile, gram negative. Normal flora of upper respiratory, intestinal, and female genital tracts. Polysaccharide capsule is the virulence factor
Mixtures of anaerobes (such as Gram positive Peptostreptococcus, Actinomyces, and Gram negative Prevotella, Prophyromonas, and Fusobacterium nucleatum) with Bacteroides fragilis can cause what
Polymicrobial infections such as peridontitis and pelvic inflammatory disease