Two novel EHEC/EAEC hybrid strains isolated from human infections.

Rita Prager,Christina Lang,Angelika Fruth,Antje Flieger,Erhard Tietze,Philipp Aurass,Michael Hensel

doi:10.1371/journal.pone.0095379

Rita Prager, Christina Lang + Show 5 more

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https://doi.org/10.1371/journal.pone.0095379

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Journal: PloS one	Publication Date: Apr 21, 2014
Citations: 94	License type: CC BY 4.0

Affiliation: Robert Koch Institute

Abstract

The so far highest number of life-threatening hemolytic uremic syndrome was associated with a food-borne outbreak in 2011 in Germany which was caused by an enterohemorrhagic Escherichia coli (EHEC) of the rare serotype O104:H4. Most importantly, the outbreak strain harbored genes characteristic of both EHEC and enteroaggregative E. coli (EAEC). Such strains have been described seldom but due to the combination of virulence genes show a high pathogenicity potential. To evaluate the importance of EHEC/EAEC hybrid strains in human disease, we analyzed the EHEC strain collection of the German National Reference Centre for Salmonella and other Bacterial Enteric Pathogens (NRC). After exclusion of O104:H4 EHEC/EAEC strains, out of about 2400 EHEC strains sent to NRC between 2008 and 2012, two strains exhibited both EHEC and EAEC marker genes, specifically were stx2 and aatA positive. Like the 2011 outbreak strain, one of the novel EHEC/EAEC harbored the Shiga toxin gene type stx2a. The strain was isolated from a patient with bloody diarrhea in 2010, was serotyped as O59:H−, belonged to MLST ST1136, and exhibited genes for type IV aggregative adherence fimbriae (AAF). The second strain was isolated from a patient with diarrhea in 2012, harbored stx2b, was typed as Orough:H−, and belonged to MLST ST26. Although the strain conferred the aggregative adherence phenotype, no known AAF genes corresponding to fimbrial types I to V were detected. In summary, EHEC/EAEC hybrid strains are currently rarely isolated from human disease cases in Germany and two novel EHEC/EAEC of rare serovars/MLST sequence types were characterized.

Highlights

Escherichia coli bacteria on the one hand belong to the normal flora of the human intestine but on the other hand may cause disease
Shiga toxin-positive strains inducing hemolytic uremic syndrome (HUS) in many cases belong to the serovar O157:H7/H2 and others such as O26:H11/H2, O103:H2/H2, O111:H8/H2, O145:H28/H2, the outbreak was caused by an E. coli strain of the rare serotype O104:H4 characterized by the presence of enterohemorrhagic E. coli (EHEC) pathovar markers as well as genes of another pathovar, enteroaggreagative E. coli (EAEC)
After the large outbreak caused by EHEC/EAEC O104:H4 in 2011, we analyzed whether additional EHEC/EAEC were among the strains deposited in the EHEC collection of the German National Reference Centre for Salmonella and other Bacterial Enteric Pathogens (NRC)

Summary

Introduction

Escherichia coli bacteria on the one hand belong to the normal flora of the human intestine but on the other hand may cause disease. Pathogenic E. coli variants harbor specific genes encoding virulence determinants [1]. Enterohemorrhagic E. coli (EHEC) are an intestinal pathovar that cause about 1,000 to 1,500 cases of diarrhea or bloody diarrhea in Germany per year and about 70 cases of the severe pathology hemolytic uremic syndrome (HUS) [2]. Shiga toxin-positive strains inducing HUS in many cases belong to the serovar O157:H7/H2 and others such as O26:H11/H2, O103:H2/H2, O111:H8/H2, O145:H28/H2, the outbreak was caused by an E. coli strain of the rare serotype O104:H4 characterized by the presence of EHEC pathovar markers as well as genes of another pathovar, enteroaggreagative E. coli (EAEC). Called mixed E. coli pathovars or hybrid strains have been seldom described and show a high virulence potential [4,5,6,7,8,9,10,11,12,13,14,15,16]

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