Observations on production of hemolysin, heat-labile enterotoxin and antimicrobial drug resistance among enterotoxigenic Escherichia coli from pigs.

A total of 52 isolates of Escherichia coli belonging to enterotoxigenic serotypes from piglets with diarrhea were examined for hemolysis, production of cholera-like enterotoxin (LT) and susceptibility to 10 antimicrobial drugs. A strong association between production of LT and hemolysis was seen. Ninety percent of 29 hemolylic isolates were LT⁺ whereas 100% of 23 nonhemolytic isolates were LT⁻ in a commercial latex agglutination assay. Antimicrobial susceptibility tests employing disc diffusion showed that resistance to trimethoprim-sulfamethoxazole (TMS), neomycin and tetracycline was significantly less among LT⁺ isolates compared to LT⁻ ones. Enrofloxacin was the only antimicrobial drug to which all the 52 isolates were susceptible.