Attaching and effacing E. coli. Microscopic and ultrastructural observation of intestinal infections in pigs.

Pigs aged from neonate to 8 weeks with naturally occurring diarrhoea were submitted to a Veterinary Investigation Centre for routine diagnosis. They were retrospectively found to be infected with "attaching and effacing" E. coli (AEEC) on histological and ultrastructural examination of the intestinal tract. Subcultures of E. coli isolated from some of the affected pigs were tested against standard anti-sera and probed for the presence of verotoxin (VT) and "cae" genes. One strain of E. coli was positive for the VT gene and three VT-negative strains possessed the "cae" gene. This preliminary report suggests that in naturally occurring diarrhoea of suckling and weaned pigs, AEEC infection can be identified by histological examination of the intestinal mucosa and confirmed by electron microscopy, in the abscence of infection by recognised enteric pathogens on microbiological examination.