Diversification of Escherichia albertii H-Antigens and Development of H-Genotyping PCR

Abstract

<i>Escherichia albertii</i> is a recently recognized human enteropathogen that is closely related to <i>Escherichia coli</i>. As <i>E. albertii</i> sometimes causes outbreaks of gastroenteritis, rapid strain typing systems, such as the O- and H-serotyping systems widely used for <i>E. coli</i>, will be useful for outbreak investigation and surveillance. Although an O-genotyping system has recently been developed, the diversity of <i>E. albertii</i> H-antigens (flagellins) encoded by <i>fliC</i> genes remains to be systematically investigated, and no H-serotyping or genotyping system is currently available. Here, we analyzed the <i>fliC</i> genes of 243 genome-sequenced <i>E. albertii</i> strains and identified 73 sequence types, which were grouped into four clearly distinguishable types designated <i>E. albertii</i> H-genotypes 1-4 (EAHg1-EAHg4). Although there was a clear sign of intraspecies transfer of <i>fliC</i> genes in <i>E. albertii</i>, none of the four <i>E. albertii</i> H-genotypes (EAHgs) were closely related to any of the 53 known <i>E. coli</i> H-antigens, indicating the absence or rare occurrence of interspecies transfer of <i>fliC</i> genes between the two species. Although the analysis of more <i>E. albertii</i> strains will be required to confirm the low level of variation in their <i>fliC</i> genes, this finding suggests that <i>E. albertii</i> may exist in limited natural hosts or environments and/or that the flagella of <i>E. albertii</i> may function in a limited stage(s) in their life cycle. Based on the <i>fliC</i> sequences of the four EAHgs, we developed a multiplex PCR-based H-genotyping system for <i>E. albertii</i> (EAH-genotyping PCR), which will be useful for epidemiological studies of <i>E. albertii</i> infections.