Establishment of a Molecular Serotyping Scheme and a Multiplexed Luminex-Based Array for Enterobacter aerogenes.

Xi Guo,Min Chen,Min Wang,Tingting Chen,Pan Wu,Lu Wang,Bin Liu,Yao Wang,Lu Feng

doi:10.3389/fmicb.2018.00501

Abstract

Serotyping based on surface polysaccharide antigens is important for the clinical detection and epidemiological surveillance of pathogens. Polysaccharide gene clusters (PSgcs) are typically responsible for the diversity of bacterial surface polysaccharides. Through whole-genome sequencing and analysis, eight putative PSgc types were identified in 23 Enterobacter aerogenes strains from several geographic areas, allowing us to present the first molecular serotyping system for E. aerogenes. A conventional antigenic scheme was also established and correlated well with the molecular serotyping system that was based on PSgc genetic variation, indicating that PSgc-based molecular typing and immunological serology provide equally valid results. Further, a multiplex Luminex-based array was developed, and a double-blind test was conducted with 97 clinical specimens from Shanghai, China, to validate our array. The results of these analyses indicated that strains containing PSgc4 and PSgc7 comprised the predominant groups. We then examined 86 publicly available E. aerogenes strain genomes and identified an additional seven novel PSgc types, with PSgc10 being the most abundant type. In total, our study identified 15 PSgc types in E. aerogenes, providing the basis for a molecular serotyping scheme. From these results, differing epidemic patterns were identified between strains that were predominant in different regions. Our study highlights the feasibility and reliability of a serotyping system based on PSgc diversity, and for the first time, presents a molecular serotyping system, as well as an antigenic scheme for E. aerogenes, providing the basis for molecular diagnostics and epidemiological surveillance of this important emerging pathogen.

Highlights

Enterobacter aerogenes is a Gram-negative bacterium that is ubiquitous in the human gastrointestinal tract and various other environments and is generally non-pathogenic to healthy humans (Chen et al, 2015)
Genomes were sequenced from two reference E. aerogenes strains from the American Type Culture Collection (ATCC), two from the German Collection of Microorganisms and Cultures (DSMZ), and 19 clinical strains that were isolated from the Shanghai Municipal Center for Disease Control and Prevention (SCDC) during 2012–2015 (Supplementary Table 1)
Characteristics of open reading frames (ORFs) for all putative Polysaccharide gene clusters (PSgcs) types are summarized in Supplementary Table 3

Summary

Introduction

Enterobacter aerogenes is a Gram-negative bacterium that is ubiquitous in the human gastrointestinal tract and various other environments and is generally non-pathogenic to healthy humans (Chen et al, 2015). E. aerogenes strains that are isolated from hospitalized patients generally exhibit high resistance to commonly used broad-spectrum antibiotics (De Gheldre et al, 1997; Chen et al, 2008; Lavigne et al, 2013). This species has been considered an important emerging multidrug resistant (MDR) pathogen over the past two decades (Chevalier et al, 2008). The protein complex Wza/b/c accepts the polymer made by Wzy and transports it to the cell surface, forming the capsule (K) antigen (Whitfield, 2006). The K-repeat polymer can be added to the lipid A/core, and this is known as the KLPS, which does not require the Wza/b/c complex (Hu et al, 2013)

Methods

Results

Conclusion