zoonoses and communicable diseases common to ... - PAHO/WHO

ENTEROCOLITIS DUE TO CLOSTRIDIUM DIFFICILE 133Some strains produce chains of two to six cells. C. difficile is generally motile inbroth cultures.C. difficile produces two types of toxins: enterotoxin A and cytotoxin B. Toxin Ais lethal to hamsters when administered orally. Toxin B is cytotoxic for cultured cellsof all types. A picogram of toxin B is enough to produce the cytotoxic effect (Catoet al., 1986). Not all strains produce toxins. Another virulence factor is a substancethat affects intestinal motility.Various subclassification schemes have been devised for a better understanding ofthe pathogenicity of C. difficile as well as for epidemiological purposes. One ofthem is based on electrophoretic patterns of proteins on the cellular surface due tothe different protein profiles produced by SDS-PAGE (polyacrylamide gel electrophoresiswith sodium dodecyl sulphate), staining and autoradiography ofradiomarked proteins. This method has made it possible to distinguish 15 types ofC. difficile (Tabaqchali, 1990). In addition, 15 serogroups were distinguished usingthe plate serotyping system. Six of these serogroups proved to be cytotoxigenic. Thecultures were isolated from patients who had pseudomembranous colitis or antibiotic-associateddiarrhea (Toma et al., 1988).Geographic Distribution: Probably worldwide. The agent has been isolatedfrom several sources, such as soil; marine sediment; and fecal matter from dogs,cats, cattle, camels, horses and other animals; as well as from people withoutdiarrhea (Cato et al., 1986). The number of animals and environmental samples(non-nosocomial) studied to determine C. difficile carriage was very limited(Levett, 1986).Occurrence in Man: The disease appears sporadically and in nosocomial outbreaks.Most cases of pseudomembranous colitis are nosocomial infections (Lyerlyet al., 1988). It is estimated that more than 90% of pseudomembranous colitis casesare due to C. difficile and that about 20% of diarrhea cases are associated withantibiotics.Occurrence in Animals: Outbreaks of enterocolitis have occurred in horses, rabbits,hamsters, guinea pigs, and dogs.In Australia, a study was done of dogs and cats treated in two veterinary clinics.C. difficile was successfully cultured in 32 of 81 fecal samples (39.5%). Of the 29animals that received antibiotics, 15 (52%) tested positive in cultures for C. difficile.There was no difference in carriage rate between dogs and cats. The environment ofboth clinics was also surveyed for contamination. In one clinic, 15 of 20 sites werecontaminated; in the other, 6 of 14 sites were contaminated. There were both cytotoxigenicand noncytotoxigenic isolates. Fifty percent of the animal isolates and71.4% of the environmental isolates were not cytotoxigenic. Both dogs and cats maybe potential reservoirs (Riley et al., 1991).The Disease in Man: C. difficile produces pseudomembranous colitis or antibiotic-associateddiarrhea in man. The clinical symptoms range from watery diarrhea,with varying degrees of abdominal pain, to pseudomembranous hemorrhagic necrotizingcolitis. Infections outside the intestine caused by C. difficile are less importantand occur less frequently. Abscesses, wound infections, pleurisy, and other organiceffects have been described. Arthritis may also occur as a complication of acute colitiscaused by C. difficile (Limonta et al., 1989).