Virulence, Antimicrobial Resistance Properties and Phylogenetic Background of Non-H7 Enteropathogenic Escherichia coli O157.

Mithila Ferdous,Anna M D Kooistra-Smid,John W A Rossen,Alexander W Friedrich,Kai Zhou

doi:10.3389/fmicb.2016.01540

Mithila Ferdous, Anna M D Kooistra-Smid + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2016.01540

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Abstract

Escherichia coli (E.coli) O157 that do not produce Shiga toxin and do not possess flagellar antigen H7 are of diverse H serotypes. In this study, the antibiotic resistance properties, genotype of a set of virulence associated genes and the phylogenetic background of E. coli O157:non-H7 groups were compared. Whole genome sequencing was performed on fourteen O157:non-H7 isolates collected in the STEC-ID-net study. The genomes were compared with E. coli O157 genomes and a typical Enteropathogenic E. coli (tEPEC) genome downloaded from NCBI. Twenty-six (86%) of the analyzed genomes had the intimin encoding gene eae but of different types mostly correlating with their H types, e.g., H16, H26, H39, and H45 carried intimin type ε, β, κ, and α, respectively. They belonged to several E. coli phylogenetic groups, i.e., to phylogenetic group A, B1, B2, and D. Seven (50%) of our collected O157:non-H7 isolates were resistant to two or more antibiotics. Several mobile genetic elements, such as plasmids, insertion elements, and pathogenicity islands, carrying a set of virulence and resistance genes were found in the E. coli O157:non-H7 isolates. Core genome phylogenetic analysis showed that O157:non-H7 isolates probably evolved from different phylogenetic lineages and were distantly related to the E. coli O157:H7 lineage. We hypothesize that independent acquisition of mobile genetic elements by isolates of different lineages have contributed to the different molecular features of the O157:non-H7 strains. Although distantly related to the STEC O157, E. coli O157:non-H7 isolates from multiple genetic background could be considered as pathogen of concern for their diverse virulence and antibiotic resistance properties.

Highlights

Enteropathogenic Escherichia coli (EPEC) was first identified in the United Kingdom in the 1940s as the cause of outbreaks of infantile diarrhea (Bray, 1945)
All of the O157:H16 isolates belonged to E. coli phylogenetic group A except strain Santai which belonged to phylogenetic group D
E. coli O157 strains are mostly known as enterohemorrhagic E. coli (EHEC) that have been associated with food born outbreaks worldwide

Summary

Introduction

Enteropathogenic Escherichia coli (EPEC) was first identified in the United Kingdom in the 1940s as the cause of outbreaks of infantile diarrhea (Bray, 1945). The genes responsible for this activity in EPEC are encoded on a 35-kb pathogenicity island (PAI) called the locus of enterocyte effacement (LEE), whereas the LEE of STEC contains some additional genes encoded within a putative prophage designated 933L (Perna et al, 1998). Both EPEC and STEC LEE encode a type III secretion system, multiple secreted proteins, and a bacterial adhesin called intimin (Nataro and Kaper, 1998). Several variants of the eae gene encoding different intimin types and subtypes are described (Oswald et al, 2000; Zhang et al, 2002; Blanco et al, 2006) and it has been suggested that different intimins may be responsible for different host tissue cell tropisms (Torres et al, 2005)

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