Comparative genetic characterization of Enteroaggregative Escherichia coli strains recovered from clinical and non-clinical settings.

Rong Zhang,Sheng Chen,Gong-Xiang Chen,Yong-Lu Huang,Edward Wai-Chi Chan,Dan-Xia Gu

doi:10.1038/srep24321

Abstract

The origin of pathogenic Enteroaggregative Escherichia coli (EAEC), a major causative agent of childhood diarrhea worldwide, remains ill-defined. The objective of this study was to determine the relative prevalence of EAEC in clinical and non-clinical sources and compare their genetic characteristics in order to identify strains that rarely and commonly cause human diarrhea. The virulence gene astA was commonly detectable in both clinical and non-clinical EAEC, while clinical isolates, but not the non-clinical strains, were consistently found to harbor other virulence factors such as aap (32%), aatA (18%) and aggR (11%). MLST analysis revealed the extremely high diversity of EAEC ST types, which can be grouped into three categories including: (i) non-clinical EAEC that rarely cause human infections; (ii) virulent strains recoverable in diarrhea patients that are also commonly found in the non-clinical sources; (iii) organisms causing human infections but rarely recoverable in the non-clinical setting. In addition, the high resistance in these EAEC isolates in particular resistance to fluoroquinolones and cephalosporins raised a huge concern for clinical EAEC infection control. The data from this study suggests that EAEC strains were diversely distributed in non-clinical and clinical setting and some of the clinical isolates may originate from the non-clinical setting.

Highlights

Diarrhea is one of the leading causes of child death in both developing and developed countries, causing an estimated 1.87 million deaths of children aged under 5 years globally each year[1]
A total of 84 isolates were confirmed to be Enteroaggregative Escherichia coli (EAEC) by HEP-2 adherence test, which depicted a characteristic aggregative adherence pattern for EAEC strains
The current study revealed the existence of three distinct categories of EAEC strains: (i) non-clinical EAEC that rarely cause human infections; (ii) virulent strains recoverable in diarrhea patients that are commonly found in the environment, such as ST38, ST10 and ST131 strains; (iii) organisms causing human infections but rarely recoverable in the environment

Summary

Introduction

Diarrhea is one of the leading causes of child death in both developing and developed countries, causing an estimated 1.87 million deaths of children aged under 5 years globally each year[1]. Among the DEC strains, EAEC is increasingly recognized for its role in causing persistent diarrhea in children, traveler’s diarrhea and AIDS-associated diarrhea in both developing and industrialized countries[3]. It has been identified as the causative agent of several diarrhea outbreaks around the world[4,5]. We performed comparative characterization on both human clinical and environmental EAEC isolates to identify the possible origin of EAEC strains that commonly cause infections in China, and characterized the molecular basis of virulence and antimicrobial resistance in such organisms

Objectives

Methods

Results

Conclusion