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Characterization of Pathogenic Escherichia coli in River Water by Simultaneous Detection and Sequencing of 14 Virulence Genes
journal contribution
posted on 2015-06-02, 00:00 authored by Ryota Gomi, Tomonari Matsuda, Yuji Fujimori, Hidenori Harada, Yasuto Matsui, Minoru YonedaThe
occurrence of pathogenic Escherichia coli in
environmental waters increases the risk of waterborne disease. In
this study, 14 virulence genes in 669 E. coli isolates
(549 isolates from the Yamato River in Japan, and 30 isolates from
each of the following hosts: humans, cows, pigs, and chickens) were
simultaneously quantified by multiplex PCR and dual index sequencing
to determine the prevalence of potentially pathogenic E. coli. Among the 549 environmental isolates, 64 (12%) were classified
as extraintestinal pathogenic E. coli (ExPEC) while
eight (1.5%) were classified as intestinal pathogenic E. coli (InPEC). Only ExPEC-associated genes were detected in human isolates
and pig isolates, and 11 (37%) and five (17%) isolates were classified
as ExPEC, respectively. A high proportion (63%) of cow isolates possessed
Shiga-toxin genes (stx1 or stx2)
and they were classified as Shiga toxin-producing E. coli (STEC) or enterohemorrhagic E. coli (EHEC). Among
the chicken isolates, 14 (47%) possessed iutA, which
is an ExPEC-associated gene. This method can determine the sequences
as well as the presence/absence of virulence genes. By comparing the
sequences of virulence genes, we determined that sequences of iutA were different among sources and may be useful for
discriminating isolates, although further studies including larger
numbers of isolates are needed. Results indicate that humans are a
likely source of ExPEC strains in the river.