Genetic Characterization of the O-Antigen and Development of a Molecular Serotyping Scheme for Enterobacter cloacae

Abstract

Enterobacter cloacae is a well-characterized opportunistic pathogen that is closely associated with various nosocomial infections. The O-antigen, which is one of the most variable constituents on the cell surface, has been used widely and traditionally for serological classification of many gram-negative bacteria. E. cloacae is divided into 30 serotypes, based on its O-antigen diversity. In this study, by using genomic and comparative-genomic approaches, we analyzed the O-antigen gene clusters of 26 E. cloacae serotypes in depth. We also identified the sero-specific gene for each serotype and developed a multiplex polymerase chain reaction (PCR) method. The sensitivity of the assay was 0.1 ng for genomic DNA and 10 3 colony forming units for pure cultures. The assay reliability was evaluated by double-blinded testing with 81 clinical strains. Furthermore, we established a valid, genome-based tool for in silico serotyping of E. cloacae. By screening 431 E. cloacae genomes deposited in GenBank, 304 were classified into current antigenic scheme, and 112 were allocated into 55 putative novel serotypes. Our results represent the first genetic basis of the O-antigen diversity and variation of E. cloacae, providing a rationale for studying the O-antigen associated evolution and pathogenesis of this bacterium. In addition, we extended the current serotyping system for E. cloacae, which is important for detection and epidemiological surveillance purposes for this important pathogen.

Distribution of Antimicrobial Resistance and Virulence Genes within the Prophage-Associated Regions in Nosocomial Pathogens

“…Interestingly, intact ENT47670 prophage, which also contained structural phage proteins, was detected in the prophage region where gtrA and gtrB were harbored (see Data Sets S3 and S5). This result indicates that gtrA and gtrB of the prophage region in E. cloacae were acquired through the transduction of ENT47670 or ENT47670-like phages ( 34 ).…”

Prophage elements function as reservoir for antibiotic resistance and virulence genes in nosocomial pathogens

“…Interestingly, intact ENT47670 prophage, which also contained structural phage proteins, was detected in the prophage region where gtrA and gtrB were harbored (Data Set S5). This result suggested that gtrA and gtrB of the prophage region in E. cloacae were acquired through the transduction of ENT47670 or ENT47670-like phages (32) (Fig. 5; Data Set S5).…”

Complete Genome Sequence of vB_EcoP_SU7, a Podoviridae Coliphage with the Rare C3 Morphotype

“…One possible explanation for SU7’s narrow host range could be its host receptor. The most common phage-host receptor for Podoviridae coliphages is the O-polysaccharide antigen of the lipopolysaccharide layer [ 55 , 56 , 57 ], which is highly variable in the Enterobacter genus [ 58 ]. It should be noted that despite being a rapid, simple, and quantitative screen, single high titer spot testing to determine host range may fail to discriminate between a phage’s ability to replicate within a host and its ability to kill the host strain, as well as result in an overestimation of phage host range and virulence [ 51 , 59 , 60 ].…”