Jenkins Claire, Tembo Mathias, Chart Henrik, Cheasty Tom, Willshaw Geraldine A, Phillips Alan D, Tompkins David, Smith Henry
Laboratory of Enteric Pathogens, Health Protection Agency, 61 Colindale Avenue, London NW9 5HT, UK.
University Department of Paediatric Gastroenterology, Royal Free Hospital, Pond Street, London NW3 QG, UK.
J Med Microbiol. 2006 Nov;55(Pt 11):1493-1497. doi: 10.1099/jmm.0.46683-0.
The aim of this study was to assess the usefulness of a multiplex PCR assay targeting the aat, aaiA and astA genes for the detection of typical and atypical enteroaggregative Escherichia coli (EAEC) in bacterial cultures from faecal samples from patients with community-acquired diarrhoea. The isolates harbouring these genes were also tested using the HEp-2 cell-adhesion assay to clarify their EAEC status. aat, aai or astA was found in E. coli faecal isolates from 39 (7.8 %) of 500 patients, and 20 of these strains adhered to HEp-2 cells in a pattern characteristic of EAEC. Eight isolates carrying the aai or astA gene but not the aat gene were shown to be HEp-2 cell test positive, although 12 strains with this genotype were HEp-2 cell test negative. Using the HEp-2 adhesion assay as the gold standard, the addition of primers detecting aaiA and astA to the aat PCR increased the number of EAEC isolates detected, but identified strains of E. coli that were not EAEC. The variety of genotypes exhibiting aggregative adherence highlights the problems associated with developing a molecular diagnostic test for EAEC. This PCR assay detects a variety of strains exhibiting characteristics of the EAEC group, making it a useful tool for identifying both typical and atypical EAEC.
本研究的目的是评估针对aat、aaiA和astA基因的多重PCR检测法在检测社区获得性腹泻患者粪便样本细菌培养物中典型和非典型肠集聚性大肠埃希菌（EAEC）方面的实用性。还使用HEp-2细胞黏附试验对携带这些基因的分离株进行检测，以明确其EAEC状态。在500例患者的大肠杆菌粪便分离株中，39例（7.8%）检测到aat、aai或astA，其中20株以EAEC特征性模式黏附于HEp-2细胞。8株携带aai或astA基因但不携带aat基因的分离株经HEp-2细胞试验显示为阳性，尽管12株具有该基因型的菌株经HEp-2细胞试验为阴性。以HEp-2黏附试验作为金标准，在aat PCR中添加检测aaiA和astA的引物可增加检测到的EAEC分离株数量，但也会鉴定出非EAEC的大肠杆菌菌株。表现出集聚性黏附的多种基因型凸显了开发EAEC分子诊断试验所面临的问题。这种PCR检测法可检测出多种具有EAEC组特征的菌株，使其成为鉴定典型和非典型EAEC的有用工具。
