Development of an O-Antigen Serotyping Scheme forCronobacter sakazakii

Abstract

ABSTRACTCronobacter sakazakiiis an opportunistic pathogen that can cause severe infections. Serotyping provides a basis for the categorization of bacterial strains and is an important tool for epidemiological and surveillance purposes. In this study, of the 135Cronobacterstrains tested initially, 119 were identified asC. sakazakiiand used. A serotyping scheme forC. sakazakiithat classifies strains based on their different O antigens was developed. Seven antisera that exhibited high agglutinin titers (>640) were produced. O2 and O6 antisera were specific for their homologous strains, O4 and O7 antisera gave heterologous titers with O1 and O6 antigens, respectively, and O1, O3, and O5 antisera cross-reacted with each other and require preabsorption with the other two antigens. All of these 119C. sakazakiistrains were clearly assigned to these seven serotypes. O1 and O2 are the dominant serotypes, comprising 69.7% of the isolates. We also characterized the O-antigen gene clusters using restriction fragment length polymorphism (RFLP). The grouping ofC. sakazakiistrains based on their RFLP banding patterns correlated well with the grouping of strains based on our serotyping scheme. The serotype scheme presented here could prove to be a useful tool for serotypingC. sakazakiiisolates.