Plasmids and the Heat-Labile Enterotoxin Operon Originating in a Clinically Isolated Strain Serotype 078:H11 of Enterotoxigenic Escherichia Coli

Abstract

Enterotoxigenic Escherichia coli is one of the important agents of diarrheal illness, whose pathogenic mechanism is well understood; it adheres to the epithelial cells of the small intestine and produces enterotoxins such as heat-labile toxin (LT) and heat-stable toxin (ST). Evans et al. (3) showed that a clinically isolated enterotoxigenic E. coli H10407 (serotype 078:H11) specifies both colonization factor antigen I (CFA/I) and enterotoxin (LT and ST) production. These genetic traits of the pathogenicity are plasmid-born (2–4, 6, 7, 9). A 56–60 million molecular weight plasmid specifying CFA/I and ST production, a 42 million molecular weight plasmid specifying “LT production” and a cryptic plasmid with 3.7–3.8 million molecular weight have been identified in E. coli H10407. In this communication, we show that E. coli H10407 carries at least four distinct species of plasmid: a CFA/I-and ST-coding plasmid, an LT- and ST-coding plasmid, a self-transmissible plasmid and a cryptic plasmid(s). Thus, E. coli H10407 carries two ST genes. We also analyzed the LT region, and succeeded in construction of recombinant plasmids which produced toxoids of LT.