MOLECULAR CHARACTERIZATION OF ESCHERICHIA-COLI STRAINS ISOLATED FROM PIGS WITH EDEMA DISEASE

The present study was conducted to investigate the epidemiological rel ationship of isolates of Escherichia coli causing edema disease, Class ical edema disease has not previously been described in Denmark, but b etween February 1994 and November 1995 cases appeared in 51 pig herds, among which direct or indirect trading contacts were confirmed for 36 of the herds, A total of 213 isolates from pigs with edema disease in Denmark and other countries and 23 E. coli O139 isolates from pigs wi th diarrhea or healthy pigs were analyzed to characterize their O sero groups, HindIII ribotypes, and pulsed-field gel electrophoresis (PFGE) types, and 183 of the isolates were also analyzed for their plasmid p rofiles, The resulting PFGE types of the isolates from pigs with edema disease were examined by cluster analysis, Ten isolates from three he rds could not be typed with the available O antisera, whereas all othe r isolates were of serotype O139. However, all isolates from pigs,vith edema disease belonged to the same HindIII ribotype, which was not ob served among the isolates from pigs with diarrhea or healthy pigs, All isolates from Danish pigs with edema disease except for three isolate s originating from two herds belonged to the same or closely related X baI PFGE types; the other three isolates were assigned to possibly rel ated types, Isolates from pigs with edema disease in different countri es belonged to different PFGE types, All isolates from Danish pigs wit h edema disease grouped together in one cluster, in contrast to isolat es from other countries, which did not form any clusters, E. coli stra ins of serogroup O139 from pigs with diarrhea or isolated from the fec es of healthy Danish pigs were very different, Plasmid profiles differ ed largely among isolates, However, among the isolates from Danish pig s with edema disease, one type predominated within herds, The present study indicated that most, if not all, of the observed cases of edema disease in Denmark were part of the same outbreak. The combination of PFGE typing and ribotyping was useful for studying the possible clonal relationship among strains, whereas plasmid profiling was less inform ative.