Characterization of Shiga-Toxin Producing Escherichia coli Isolated From
Cattle and Sheep in Xinjiang Province, China, Using Whole-Genome
Shiga toxin-producing Escherichia coli (STEC) is an important foodborne
pathogen capable of causing severe gastrointestinal diseases in humans.
Cattle and sheep are the natural reservoir hosts of STEC strains.
Previously, we isolated 56 STEC strains from anal and carcass swab
samples of cattle and sheep in farms and slaughterhouses. In this study,
we performed whole-genome sequencing of these isolates and determined
their serotypes, virulence profiles, sequence types (STs), and genetic
relationships. Our results showed that the 56 isolates belong to 20
different STs, 29 O:H serotypes, and 8 stx subtype combinations. The
highly prevalent serotypes were O8:H25 and O87:H16 for bovine and ovine
isolates, respectively. Five serotypes of cattle or sheep isolates are
novel. The majority (63%) of cattle isolates contain stx1+stx2,
subtyped into stx1a, stx2a, and stx2c. In contrast, most of the sheep
isolates contain stx1 only, primarily subtyped into stx1a and stx1c.
None of the isolates tested eae-positive, but virulence factors such as
ehxA and espP were present with variable prevalence rates. The
prevalence of saa (19.6%) and espP (12.5%) in cattle isolates is much
higher than that in sheep isolates, whereas that of subA (34%), katP
(14.3%), and ireA (28.6%) in sheep isolates is considerably higher
than that in cattle isolates. Core-genome SNP analysis revealed that the
majority of isolates could be clustered based on their serotypes or STs,
whereas some clustering is associated with more than one ST or serotype.
Seven-gene Multilocus Sequence Typing (MLST) indicated that nine sheep
isolates and four cattle isolates were related to a few E. coli isolates
associated with human HUS, suggesting their potential in causing severe
human infections. Collectively, we described the characteristics of
cattle and sheep STEC isolates from Xinjiang, China, which may be
utilized in comparative studies of other geographic regions and sources
of isolation and for surveillance.