Effect of chlorine injury on heat-labile enterotoxin production in enterotoxigenic Escherichia coli

Heat-labile enterotoxin (LT) production was examined in chlorine-injured and noninjured populations of enterotoxigenic Escherichia coli (ETEC) by passive immune hemolysis and Y-1 mouse adrenal tumor cell assays. Sublethally injured populations showed reduced LT production after 1, 2.5, and 4 h incubation in trypticase soy broth plus 0.25% glucose, pH 8.0. Reduction was observed during injury, resuscitation, and for at least 1.5 h following repair. LT levels comparable with that present in noninjured cells were found after 24 h incubation in the same medium, indicating delayed toxigenesis rather than permanent damage. Chlorinated populations failed to incorporate [14C]glucose until repair was completed suggesting a possible explanation for delayed toxin production. The results indicate a temporary loss of virulence among sublethally injured ETEC in chlorinated waters.