Biochemical characteristics of enterotoxigenic and nonenterotoxigenic Escherichia coli isolated from calves with diarrhea.

Eighteen isolates of enterotoxigenic Escherichia coli (ETEC) and 15 isolates of nonenterotoxigenic E coli (NETEC) obtained from calves with diarrheal disease were characterized biochemically. Of 64 biochemical tests employed, none allowed making differentiation of ETEC from NETEC. Eleven tests were used to separate ETEC isolates into 1 of 5 biotypes, although the ability to ferment dulcitol, salicin, sucrose, and sorbose gave sufficient information to identify the 5 biotypes of ETEC. The biotype data were confirmed upon testing 159 additional isolates of ETEC of bovine origin. All isolates of ETEC studied belong to serogroups O9:K35, O101:K30, O8:K85, O20:K? O8:K25, and O101:K28. The ETEC in different serogroups were also different biotypically, with the exception that isolates in serogroups O101:K28 and O101:K30 were of the same biotype. The K99 antigen was detected in 172 of the 177 isolates of ETEC and in 1 of 15 isolates of NETEC. Marked biochemical differences were not found between K99 + and K99- isolates of E coli.