Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Higashi-ku, Fukuoka, Japan.
Microb Pathog. 2010 Nov;49(5):246-51. doi: 10.1016/j.micpath.2010.06.005. Epub 2010 Jun 15.
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.
产志贺毒素大肠杆菌（STEC）可引起人类严重疾病，如出血性结肠炎和溶血尿毒综合征。本研究对日本南部地区患者的 120 株 STEC 和肠出血性大肠杆菌（EHEC）临床分离株的志贺毒素（stx）基因进行了基因分析。鉴定出 88 株 stx(1)(+)和 103 株 stx(2)(+)菌株。我们进一步通过反向间接血凝试验（RPLA）和 Vero 细胞毒性试验鉴定出 12 株stx(1)(+)和 stx(2)(+)分离株表达少量或不表达志贺毒素 1（Stx(1))和/或 2（Stx(2))。其中，1 株不能产生 Stx(1)，8 株不能产生 Stx(2)，3 株均不能产生。后 3 株中有 2 株为非 O157 血清型。大多数 Stx RPLA 阴性株属于 stx(1)/stx(2)亚型（11/12，[91.7%])。我们的定量逆转录 PCR 分析表明，RPLA 阴性株中 stx 基因转录效率较低。这是首次从 stx(1)携带株和非 O157 株中分离出具有 Stx 阴性表型的 stx 阳性株的报道。
