Serotypes and Virulence Profiles of Non-O157 Shiga Toxin-Producing Escherichia coli Isolates from Bovine Farms

Abstract

Non-O157 Shiga toxin-producing Escherichia coli (STEC) strains are clinically significant food-borne pathogens. However, there is a dearth of information on serotype prevalence and virulence gene distribution, data essential for the development of public health protection monitoring and control activities for the meat and dairy industries. Thus, the objective of this study was to examine the prevalence of non-O157 STEC on beef and dairy farms and to characterize the isolates in terms of serotype and virulence markers. Bovine fecal samples (n ‫؍‬ 1,200) and farm soil samples (n ‫؍‬ 600) were collected from 20 farms throughout Ireland over a 12-month period. Shiga toxin-positive samples were cultured and colonies examined for the presence of stx 1 and/or stx 2 genes by PCR. Positive isolates were serotyped and examined for a range of virulence factors, including eaeA, hlyA, tir, espA, espB, katP, espP, etpD, saa, sab, toxB, iha, lpfA O157/OI-141 , lpfA O113 , and lpfA O157/OI-154 . Shiga toxin and intimin genes were further examined for known variants. Significant numbers of fecal (40%) and soil (27%) samples were stx positive, with a surge observed in late summer-early autumn. One hundred seven STEC isolates were recovered, representing 17 serotypes. O26:H11 and O145:H28 were the most clinically significant, with O113:H4 being the most frequently isolated. However, O2:H27, O13/O15:H2, and ONT:H27 also carried stx 1 and/or stx 2 and eaeA and may be emerging pathogens.

Shiga Toxin Subtypes and Virulence Genes in <i>Escherichia coli</i> Isolated from Cattle

“…Since serotypes of O8:H19, O113:H21, O174:H21, and O178:H19 have been frequently isolated from cattle and found to be eae-negative, the prevalence of putative adhesion genes has been extensively investigated (16,23,24). Our results from O8:H19 and O113:H21 strains carrying stx2a, saa, iha, espP, and lpfA O113 are consistent with those of previous reports (23).…”

“…saa, which is the major adherence factor gene in eae-negative STEC (16), was detected in 16 strains (36z). As previously reported (16), all saa-positive strains were eae-negative. toxB was detected only in O157.…”

“…cdtIII and cnf2 coexisted in 2 strains (O1:H7 and O183:H18), and cdtV was detected in O113:H-. Forty-five cattle isolates were tested for 5 putative adhesion genes (saa, iha espP, toxB, and lpfA O113 ) that have been detected previously in non-O157 STEC strains (16). saa, which is the major adherence factor gene in eae-negative STEC (16), was detected in 16 strains (36z).…”

“…Previously mentioned PCR primers (13) were used to detect and subtype cdt and cnf. Putative adhesin genes (saa, iha, toxB, espP, and lpfA O113 ) were detected by PCR using primers described by Monaghan et al (16) and the conditions described by Tatarczak et al (17).…”

Comparison of Three Molecular Subtyping Methods among O157 and Non-O157 Shiga Toxin-Producing <i>Escherichia coli</i> Isolates from Japanese Cattle

“…In contrast, multilocus sequence typing (MLST) is easy to apply to interlaboratory and worldwide comparisons of E. coli isolates, and currently, there are 7,116 sequence types (STs; available at <http: pubmlst.org databases.shtml>, accessed September 20, 2017). Although the prevalence and virulence profiles of bovine non-O157 STEC isolates have been reported (14)(15)(16)(17)(18)(19), little is known about the application and comparison of several typing methods involving bovine isolates, and there are many publications reporting application these subtyping methods to non-O157 STEC strains (20)(21)(22). There are no reports comparing bovine STEC isolates by major subtyping methods (that is PFGE, MLVA, and MLST).…”