Shiga toxin- and enterotoxin-producing Escherichia coli isolated from subjects with bloody and nonbloody diarrhea in Bangkok, Thailand

Abstract

A total of 314 stool samples collected from 92 subjects with bloody diarrhea, 119 subjects with non-bloody diarrhea and 103 normal subjects in Bangkok, Thailand, were investigated for the presence of Shiga toxin-producing Escherichia coli (STEC) and enterotoxin-producing E. coli (ETEC) by multiplex PCR assay. Virulence genes and cytotoxic effect to Vero cells of STEC were also determined. STEC (5 isolates) and ETEC (18 isolates) were detected in 3 and 14 subjects, respectively. Among subjects containing ETEC, only one person belonged to normal control group. The detected STEC included two isolates (serotypes O26:H − and O111:H −) of Shiga toxin type 1 (Stx1-only) STEC from a child with non-bloody diarrhea, two isolates (Stx1–Stx2 STEC and Stx1-only STEC) from an adult with bloody diarrhea, and one isolate of Stx1–Stx2v STEC (O157:H7) from normal child. Only Stx1–Stx2 STEC isolate was found to exhibit toxicity to Vero cells and carry hlyA gene. The intimin encoding gene locus eaeA was not detected in any isolate. These results indicate that most of STEC isolates in Thailand were low virulent.