Shiga toxin-producing Escherichia coli (STEC) can cause severe illnesses in humans such as hemorrhagic colitis and hemolytic-uremic syndrome. In this study, we carried out genotypic analysis of the Shiga toxin (stx) gene in 120 clinical isolates of STEC and enterohemorrhagic E. coli (EHEC) from patients in a southern district of Japan. We identified 88 stx 1 + and 103 stx 2 + strains. We further identified 12 stx 1 + and stx 2 + isolates expressing little or no Shiga toxin 1 (Stx 1 ) and/or 2 (Stx 2 ) by reversed passive latex agglutination (RPLA) and Vero cell toxicity assays. Among them, 1 strain could not produce Stx 1 , 8 could not produce Stx 2 , and 3 strains could produce neither. Two of the latter three strains were of the non-O157 serotype. Most of the Stx RPLA-negative strains belonged to the stx 1 /stx 2 subtype (11/12, [91.7%]). Our quantitative reverse transcription PCR analysis indicated that the stx genes were not effectively transcribed in the RPLA-negative strains. This is the first report of the isolation of stx-positive strains showing Stx-negative phenotype from stx 1 -bearing strains and non-O157 strains.
All Science Journal Classification (ASJC) codes
- Infectious Diseases