Isolation and Characteristics of Shiga Toxin 2f-Producing Escherichia coli among Pigeons in Kyushu, Japan

Koichi Murakami,Eriko Maeda,Sachiko Ichihara,Kimiko Kawano,Hiroshi Narimatsu,Yoshiaki Kawamura,Yoshiki Etoh,Kenitiro Ito,Shigeyuki Takenaka,Kazumi Horikawa,Dongsheng Zhou

doi:10.1371/journal.pone.0086076

Abstract

An increasing number of Shiga toxin 2f-producing Escherichia coli (STEC2f) infections in humans are being reported in Europe, and pigeons have been suggested as a reservoir for the pathogen. In Japan, there is very little information regarding carriage of STEC2f by pigeons, prompting the need for further investigation. We collected 549 samples of pigeon droppings from 14 locations in Kyushu, Japan, to isolate STEC2f and to investigate characteristics of the isolates. Shiga toxin stx 2f gene fragments were detected by PCR in 16 (2.9%) of the 549 dropping samples across four of the 14 locations. We obtained 23 STEC2f-isolates from seven of the original samples and from three pigeon dropping samples collected in an additional sampling experiment (from a total of seven locations across both sampling periods). Genotypic and phenotypic characteristics were then examined for selected isolates from each of 10 samples with pulsed-field gel electrophoresis profiles. Eight of the stx 2f gene fragments sequenced in this study were homologous to others that were identified in Europe. Some isolates also contained virulence-related genes, including lpfA O26, irp 2, and fyuA, and all of the 10 selected isolates maintained the eae, astA, and cdt genes. Moreover, five of the 10 selected isolates contained sfpA, a gene that is restricted to Shiga toxin-producing E. coli O165:H2 and sorbitol-fermenting Shiga toxin-producing E. coli O157:NM. We document serotypes O152:HNM, O128:HNM, and O145:H34 as STEC2f, which agrees with previous studies on pigeons and humans. Interestingly, O119:H21 was newly described as STEC2f. O145:H34, with sequence type 722, was described in a German study in humans and was also isolated in the current study. These results revealed that Japanese zoonotic STEC2f strains harboring several virulence-related factors may be of the same clonal complexes as some European strains. These findings provide useful information for public health-related disease management strategies in Japan.

Highlights

Recent reports have shown that cases of human infection by Shiga toxin 2f-producing Escherichia coli (STEC2f) are becoming more frequent, with pigeons being implicated as a possible source of infection [1,2]
Sonntag et al [5] showed that a STEC2f O128:HNM strain from human diarrhea was identical to those of pigeon isolates belonging to the serotype O128:H2, based on the restriction fragment length polymorphism pattern identified in Germany
Detection of Shiga toxin 2f-producing E. coli In experiment 1, stx2f was detected in 16 (2.9%) of 549 dropping cultures from four of the 14 locations by PCR

Summary

Introduction

Recent reports have shown that cases of human infection by Shiga toxin 2f-producing Escherichia coli (STEC2f) are becoming more frequent, with pigeons being implicated as a possible source of infection [1,2]. Sonntag et al [5] showed that a STEC2f O128:HNM strain from human diarrhea was identical to those of pigeon isolates belonging to the serotype O128:H2, based on the restriction fragment length polymorphism pattern identified in Germany. These studies have shown that the occurrence of STEC2f in humans is clearly higher than previously thought, and that zoonotic transfer from pigeons is a potentially serious threat

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