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

94 BACTERIOSESvolunteers indicate that a very high bacterial load is needed to reproduce the disease.Some outbreaks due to contaminated water and food have occurred in the developedcountries.EIEC can be suspected when a large number of leukocytes is found in a preparationmade from fecal mucus. The guinea pig-keratoconjunctivitis test (Sereny test)has diagnostic value. This test uses enteroinvasive E. coli cultures to demonstrate thecapacity to invade epithelial cells. An enzyme immunoassay has been developed todetect a polypeptide in the surface membrane of the bacteria that determines virulence(invasive capacity).d) Enteropathogenic E. coli (EPEC). The etiologic agents of the enteropathogenicdisease belong to 15 O serogroups of E. coli. The disease occurs primarily innursing babies under 1 year, in whom it can cause a high mortality rate.The disease is characterized by watery diarrhea containing mucus but no visibleblood; fever; and dehydration. The incubation period is short.The disease occurs primarily in developing countries and has practically disappearedin Europe and the US. It occurs mostly in the warm seasons (summer diarrhea)and the sources of infection are formula milk and weaning foods that becomecontaminated due to poor cleaning of bottles and nipples, or deficient hygiene on themother’s part. Children in poor socioeconomic groups are frequently exposed toEPEC and generally acquire immunity after the first year of life. In epidemic diarrheain newborns in nurseries, airborne transmission is possible through contaminateddust. Some outbreaks have also been described in adults.E. coli isolated from feces must be serotyped. Once the EPEC serotype has beendetermined, a DNA probe should be used to try to identify the EPEC adherence factor(EAF), which is plasmid-dependent. EPEC strains also show localized adherenceto HEp-2 cells.In epidemics, hospitals and nurseries should have a separate room for sick babies.Treatment consists primarily of electrolyte replacement with oral saline solutions, orwith intravenous solutions, if necessary. In most cases, no other treatment is needed.In serious cases, the child can be given oral cotrimoxazole, which reduces the intensityand duration of the diarrhea. Feeding, including breast-feeding, should continue(Benenson, 1990).e) Enteroaggregative E. coli (EAggEC). This name is given to a group of E. colithat has an aggregative adherence pattern in an HEp-2 assay rather than a localized(as in EPEC) or diffuse one. This category is provisional until it is better defined. Astudy was done on 42 cultures—40 from children with diarrhea in Santiago (Chile),1 from Peru, and 1 from a North American student who had visited Mexico. Allthese strains tested negative for enterohemorrhagic, enterotoxigenic, enteropathogenic,and enteroinvasive E. coli with DNA probes. They also failed to fit in one ofthese categories on the basis of serotyping. This group causes characteristic lesionsin rabbit ligated ileal loops and mice (Vial et al., 1988; Levine et al., 1988).EAggEC causes persistent diarrhea in nursing babies. The incubation period isestimated at one to two days (Benenson, 1990).The Disease in Animals: In addition to sporadic cases of mastitis, urogenitalinfections, abortions, and other pathological processes, E. coli is responsible for severalimportant diseases.