Relative importance of enterotoxigenic and invasive enteropathogenic bacteria in infantile diarrhoea.

Swedish children and adults (648 patients) with acute diarrhoea were investigated for enterotoxigenic strains in stool cultures. A total number 74 strains were isolated from 28 patients and assayed in the rabbit intestinal loop test and the adrenal cell test. Only three of the enterotoxigenic E. coli (ETEC) isolates belonged to classical enteropathogenic serotypes of E. coli (EPEC). Two enterotoxigenic strains of Proteus morganii, two of Enterobacter hafniae and one of Citrobacter freundii were isolated. None of 67 EPEC strains were found to produce a heat-labile enterotoxin (LT) in either of the two test systems. A number of Yersinia enterocolitica and Pseudomonas aeruginosa strains from stool cultures often produced toxic effects in the cell test but no enterotoxin activity was detected for any of the strains investigated either in the adrenal cell test for heat-labile enterotoxin (LT) or the suckling mouse test for heat-stable enterotoxin (ST). All EPEC isolates were also tested for ST and for invasive properties in the Sereny test; each isolate was negative in both test systems. It is concluded that production of LT and ST enterotoxin were common in stool isolates from Ethiopian children but a rare phenomenon among Swedish children with acute infantile diarrhoea. Isolation of aerobic stool bacteria with invasive properties seems to be uncommon both in Ethiopian and Swedish children. However, since both LT and ST as well as invasive properties seem to be very unstable genetic properties in many of these stool isolates improved sensitive methods for the last two properties will probably change this picture in the future.