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首页> 外文期刊>BMC Microbiology >Characterisation of atypical enteropathogenic E. coli strains of clinical origin
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Characterisation of atypical enteropathogenic E. coli strains of clinical origin

机译：临床来源的非典型肠致病性大肠杆菌菌株的表征

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Background Enteropathogenic E. coli (EPEC) is a prominent cause of diarrhoea, and is characterised in part by its carriage of a pathogenicity island: the locus for enterocyte effacement (LEE). EPEC is divided into two subtypes according to the presence of bundle-forming pili (BFP), a fimbrial adhesin that is a virulence determinant of typical EPEC (tEPEC), but is absent from atypical EPEC (aEPEC). Because aEPEC lack BFP, their virulence has been questioned, as they may represent LEE-positive Shiga toxin-producing E. coli (STEC) that have lost the toxin-encoding prophage, or tEPEC that have lost the genes for BFP. To determine if aEPEC isolated from humans in Australia or New Zealand fall into either of these categories, we undertook phylogenetic analysis of 75 aEPEC strains, and compared them with reference strains of EPEC and STEC. We also used PCR and DNA hybridisation to determine if aEPEC carry virulence determinants that could compensate for their lack of BFP. Results The results showed that aEPEC are highly heterogeneous. Multilocus sequence typing revealed that 61 of 75 aEPEC strains did not belong to known tEPEC or STEC clades, and of those that did, none expressed an O:H serotype that is frequent in tEPEC or STEC strains associated with disease. PCR for each of 18 known virulence-associated determinants of E. coli was positive in less than 15% of strains, apart from NleB which was detected in 30%. Type I fimbriae were expressed by all aEPEC strains, and 12 strains hybridised with DNA probes prepared from either bfpA or bfpB despite being negative in the PCR for bfpA. Conclusion Our findings indicate that clinical isolates of aEPEC obtained from patients in Australia or New Zealand are not derived from tEPEC or STEC, and suggest that functional equivalents of BFP and possibly type I fimbriae may contribute to the virulence of some aEPEC strains.
机译：背景肠致病性大肠杆菌（EPEC）是引起腹泻的主要原因，其部分特点是带有致病岛：肠上皮细胞受损的场所（LEE）。根据成束菌毛（BFP）的存在将EPEC分为两种亚型，BFP是典型的ECEC（tEPEC）的毒性决定因素，而非典型EPEC（aEPEC）所不具有的纤维粘附素。由于aEPEC缺乏BFP，因此它们的毒力受到了质疑，因为它们可能代表丢失了毒素编码原语的LEE阳性志贺毒素生产大肠杆菌（STEC）或丢失了BFP基因的tEPEC。为了确定从澳大利亚或新西兰的人类中分离出的aEPEC是否属于上述两类，我们对75种aEPEC菌株进行了系统发育分析，并将其与EPEC和STEC的参考菌株进行了比较。我们还使用了PCR和DNA杂交技术来确定aEPEC是否携带能决定其BFP缺乏的毒力决定簇。结果结果表明，aEPEC是高度异质的。多基因座序列分型显示，在75个aEPEC菌株中，有61个不属于已知的tEPEC或STEC进化枝，而在那些菌株中，没有一个表达与疾病相关的tEPEC或STEC菌株中常见的O：H血清型。在不到15％的菌株中，与大肠杆菌相关的18个已知毒力相关决定簇的PCR均呈阳性，而在30％的NleB中检测到。所有aEPEC菌株均表达I型菌毛，并且12株菌株与从bfpA或bfpB制备的DNA探针杂交，尽管在PCR中对bfpA阴性。结论我们的发现表明，从澳大利亚或新西兰患者那里获得的aEPEC的临床分离株并非来源于tEPEC或STEC，并且表明BFP的功能等同物和可能的I型菌毛可能对某些aEPEC菌株的毒力有所贡献。

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