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 103 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.
Highlights
Enterobacter cloacae, which is ubiquitous in soil, water, and sewage, is a well-known human opportunistic pathogen that is frequently responsible for nosocomial infections contributing to bacteremia, endocarditis, septic arthritis, osteomyelitis, skin/soft tissue infections, and lower respiratory tract, urinary tract, and intra-abdominal infections (Fata et al, 1996; Mezzatesta et al, 2012; Davin-Regli and Pagès, 2015)
Twenty-six O-antigen gene cluster (O-AGC) of E. cloacae reference strains collected from National Collection of Type Cultures, United Kingdom (NCTC) were obtained via genome sequencing
All O-AGCs are located between two housekeeping genes, galF and gnd, and range from 4,473 to 16,323 bp, with all genes being transcribed from galF and gnd and five to 16 open reading frames (ORFs) being encoded
Summary
Enterobacter cloacae, which is ubiquitous in soil, water, and sewage, is a well-known human opportunistic pathogen that is frequently responsible for nosocomial infections contributing to bacteremia, endocarditis, septic arthritis, osteomyelitis, skin/soft tissue infections, and lower respiratory tract, urinary tract, and intra-abdominal infections (Fata et al, 1996; Mezzatesta et al, 2012; Davin-Regli and Pagès, 2015). Lipopolysaccharide (LPS), which is a hallmark structural entity, is essential for membrane stability and cell survival and is a key virulence determinant for many gram-negative bacterial species. The O-antigen contributes the most to cell-surface diversity in gram-negative bacteria, offering a selective advantage in its specific niche (Reeves, 1992; Wang et al, 2010), and is an key virulence factor associated with bacterial pathogenesis (March et al, 2013; Sarkar et al, 2014; Caboni et al, 2015). Considerable variation of the O-antigen composition provides a basis for serotyping schemes with many gram-negative bacteria, which has been recognized one of the most important cell constituents in typing strains, and a basic tool utilized in outbreak investigations and epidemiological survey (Kenyon et al, 2017; DebRoy et al, 2018; Guo et al, 2018; Qian et al, 2018)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
