Identification serologically, chemically and genetically of two Escherichia coli strains as candidates for new O serogroups

Escherichia coli strains are normally identified by the combination of their O and H (and sometimes K) antigens, and serotyping based on the antigens is believed to be crucial for clinical detection and epidemiological investigation. Two E. coli strains, G5413 and G5287, were isolated from faecal samples of female patients with diarrhoea and were not agglutinated with any antisera that cover the well-known O serogroups of E. coli. We elucidated the O-polysaccharide (OPS) structures and analysed the O-antigen gene clusters of these bacteria. The OPS structure of G5413 established by monosaccharide analysis and NMR spectroscopy was found to be unique amongst known bacterial polysaccharide structures. The O-antigen gene cluster of this strain was sequenced and did not match sequence data with any of the 184 O serogroups that have been recognized internationally. Gene functions were tentatively assigned and were appropriate to the OPS structure. Based on these data, we suggest G5413 as a candidate for a new E. coli O serogroup. Both the OPS structure and O-antigen gene cluster of G5287 were identical to those of E. coli L-19, a candidate for another new O serogroup characterized by us recently. Recognition of these two provisional O serogroups increases the number of known O-antigen forms of E. coli to 186.

通常通过其O和H（有时是K）抗原的组合来鉴定大肠杆菌菌株，基于抗原的血清分型被认为对于临床检测和流行病学研究至关重要。从腹泻女性患者的粪便样本中分离出两个大肠杆菌菌株G5413和G5287，并未用任何覆盖大肠杆菌的O血清群的抗血清凝集。我们阐明了O-丙糖糖（OPS）结构，并分析了这些细菌的O-抗原基因簇。发现通过单糖分析和NMR光谱建立的G5413的OPS结构在已知的细菌多糖结构中是独一无二的。测序了该菌株的O-抗原基因簇，并且与在国际上识别的184 O血清群中的任何一个都不匹配序列数据。基因函数暂定分配，并适合OPS结构。基于这些数据，我们建议G5413作为新的大肠杆菌o的候选者。 G5287的OPS结构和O-抗原基因簇都与大肠杆菌L-19的OPS结构相同，该大肠杆菌L-19最近是我们最近以我们为特征的另一种新的O血清群的候选者。对这两个临时O血清群的识别将已知的O-抗原形式的大肠杆菌数量增加到186。