Elicitation of enteroluminal neutrophils by enterotoxigenic and nonenterotoxigenic strains of Escherichia coli in swine

Abstract

In intact neonatal piglets, two strains of enterotoxigenic Escherichia coli (ETEC), which could adhere to epithelial cells and thus colonize the small intestine, attracted greater numbers of neutrophils into the lumen and wall of the intestine than did a nonenteropathogenic strain of E. coli. Ligated loops of small intestine in 8-week-old pigs were used in attempts to identify the attributes of ETEC involved in stimulating an increased enteroluminal migration of neutrophils. A nonenteropathogenic strain of E. coli did not attract neutrophils into the intestinal lumen in this model. However, three of the five ETEC strains tested did so. The three positive strains all produced heat-stable enterotoxin type b (STb). Neither of the negative ETEC strains produced STb. An STb-containing culture supernatant prepared from a strain of E. coli which contained an STb plasmid did not attract significantly more neutrophils than did a control supernatant prepared from the same strain of E. coli without the plasmid. The ETEC strains which attracted neutrophils in loops did not associate intimately with loop villi more consistently, nor did they grow to higher numbers in loops than strains which did not. It was concluded that there are increased numbers of neutrophils in the intestinal lumen during ETEC infection of newborn pigs. However, attempts to identify the attribute(s) of ETEC responsible for eliciting enteroluminal neutrophils were not successful.