Diversity of O Antigens within the Genus Cronobacter: from Disorder to Order

Abstract

ABSTRACTCronobacterspecies are Gram-negative opportunistic pathogens that can cause serious infections in neonates. The lipopolysaccharides (LPSs) that form part of the outer membrane of such bacteria are possibly related to the virulence of particular bacterial strains. However, currently there is no clear overview of O-antigen diversity within the variousCronobacterstrains and links with virulence. In this study, we tested a total of 82 strains, covering each of theCronobacterspecies. The nucleotide variability of the O-antigen gene cluster was determined by restriction fragment length polymorphism (RFLP) analysis. As a result, the 82 strains were distributed into 11 previously published serotypes and 6 new serotypes, each defined by its characteristic restriction profile. These new serotypes were confirmed using genomic analysis of strains available in public databases: GenBank and PubMLSTCronobacter. Laboratory strains were then tested using the current serotype-specific PCR probes. The results show that the current PCR probes did not always correspond to genomic O-antigen gene cluster variation. In addition, we analyzed the LPS phenotype of the reference strains of all distinguishable serotypes. The identified serotypes were compared with data from the literature and the MLST database (www.pubmlst.org/cronobacter/). Based on the findings, we systematically classified a total of 24 serotypes for theCronobactergenus. Moreover, we evaluated the clinical history of these strains and show thatCronobacter sakazakiiO2, O1, and O4,C. turicensisO1, andC. malonaticusO2 serotypes are particularly predominant in clinical cases.