MM. Medical Microbiology, 8th Edition, Clostridium, PDF

CHAPTER 30 CLOSTRIDIUM The genus Clostridium consists of a large heterogeneous collection of spore-forming anaerobic rods. Pathogens such as Clostridium tetani and Clostridium botulinum, the agents responsible for tetanus and botulism, r...

CHAPTER 30 CLOSTRIDIUM The genus Clostridium consists of a large heterogeneous collection of spore-forming anaerobic rods. Pathogens such as Clostridium tetani and Clostridium botulinum, the agents responsible for tetanus and botulism, respectively, are well recognized and have historical significance, and disease caused by Clostridium difficile has evolved in recent years as an infectious complication of antibiotic usage, in both the hospital and the community. Other species of clostridia are also well-recognized pathogens. 1. Clostridium perfringens is an important cause of myonecrosis. What virulence factors are responsible for this disease? 2. Food poisoning caused by C. perfringens and C. botulinum is caused by ingestion of toxins (intoxication). Compare the clinical manifestations of these two diseases. 3. What disease is caused by Clostridium septicum, and what patient population is most susceptible? Answers to these questions are available on StudentConsult.com. SUMMARIES CLINICALLY SIGNIFICANT ORGANISMS Clostridium difficile Spores can be detected in hospital rooms of Relapse is common because antibiotics do infected patients (particularly around beds not kill spores; a second course of therapy Trigger Words and in bathrooms); these can be an with the same antibiotic is usually Spore-former, fecal carriage, antibiotic- exogenous source of infection successful, although multiple courses may associated diarrhea, toxins A and B A highly virulent strain of C. difficile currently be necessary causes disease in communities and hospitals The hospital room should be carefully cleaned Biology and Virulence in Canada, the United States, and Europe after the infected patient is discharged Large anaerobic rod characterized by abundant spore formation, rapid growth, Diseases Clostridium perfringens and production of volatile fatty acids Antibiotic-associated diarrhea: acute Trigger Words Most strains produce two toxins: an diarrhea generally developing 5 to 10 days enterotoxin that attracts neutrophils and Weak spore-former, environmental, after initiation of antibiotic treatment; may stimulates their release of cytokines, and a myonecrosis, sepsis, food poisoning, be brief and self-limited or more protracted cytotoxin that increases permeability of the surgical debridement Pseudomembranous colitis: most severe intestinal wall and subsequent diarrhea form of C. difficile disease, with profuse Spore formation allows the organism to Biology and Virulence diarrhea, abdominal cramping, and fever; persist in the hospital environment and whitish plaques (pseudomembranes) form Large gram-positive rods with spores rarely resist decontamination efforts over intact colonic tissue observed Resistance to antibiotics such as Distinct colony morphology and rapid clindamycin, cephalosporins, and Diagnosis growth fluoroquinolones allows C. difficile to Produces many toxins and enzymes that overgrow the normal intestinal bacteria in C. difficile disease is confirmed by detecting lyse blood cells and destroy tissues, leading patients exposed to these antibiotics and cytotoxin or enterotoxin or the toxin genes to diseases such as overwhelming sepsis, produce disease in the patient’s feces massive hemolysis, and myonecrosis Produces a heat-sensitive enterotoxin that Epidemiology Treatment, Prevention, and Control binds to receptors on the epithelium of the Colonizes the intestines of a small The implicated antibiotic should be small intestine, leading to loss of fluids and proportion of healthy individuals (90%; macular; No 10-25 spotted fever nausea, vomiting, abdominal pain centripetal spread Rickettsialpox 9-14 Abrupt onset; fever, headache, chills, myalgias, 100%; papulovesicular; Yes Low photophobia generalized Epidemic typhus 8 Abrupt onset; fever, headache, chills, myalgias, 20%-80%; macular; No 20 arthralgia centrifugal spread Endemic typhus 7-14 Gradual onset; fever, headache, myalgias, cough 50%; maculopapular No Low rash on trunk Scrub typhus 10-12 Abrupt onset; fever, headache, myalgias