Pathogenic and phylogenetic characteristics of non-O157 Shiga toxin-producingEscherichia coliisolates from retail meats in South Korea

Abstract

Herein, we report the pathogenic and phylogenetic characteristics of seven Shiga toxin (Stx)-producing Escherichia coli (STEC) isolates from 434 retail meats collected in Korea during 2006 to 2012. The experimental analyses revealed that all isolates (i) were identified as non-O157 STEC, including O91:H14 (3 isolates), O121:H10 (2 isolates), O91:H21 (1 isolate), and O18:H20 (1 isolate), (ii) carried diverse Stx subtype genes (stx1, stx2c, stx2e, or stx1 + stx2b) whose expression levels varied strain by strain, and (iii) lacked the locus of enterocyte effacement (LEE) pathogenicity island, a major virulence factor of STEC, but they possessed one or more alternative virulence genes encoding cytotoxins (Cdt and SubAB) and/or adhesins (Saa, Iha, and EcpA). Notably, a significant heterogeneity in glutamate-induced acid resistance was observed among the STEC isolates (p < 0.05). In addition, phylogenetic analyses demonstrated that all three STEC O91:H14 isolates were categorized into sequence type (ST) 33, of which two beef isolates were identical in their pulsotypes. Similar results were observed with two O121:H10 pork isolates (ST641; 88.2% similarity). Interestingly, 96.0% of the 100 human STEC isolates collected in Korea during 2003 to 2014 were serotyped as O91:H14, and the ST33 lineage was confirmed in approximately 72.2% (13/18 isolates) of human STEC O91:H14 isolates from diarrheal patients.

O-serogroups, virulence genes, antimicrobial susceptibility, and MLST genotypes of Shiga toxin-producing Escherichia coli from swine and cattle in Central China

“…In addition, the sequence types of the two STEC O157 were determined as ST542 (Table 1). Although the sequence type of STEC O157 is normally determined as ST11 [61, 72], O157 isolates determined as non-ST11 have been also documented elsewhere. For instance, four O157 isolates from the US and/or UK are determined as ST1804 [62].…”

Host response to the subtilase cytotoxin produced by locus of enterocyte effacement‐negative Shiga‐toxigenic Escherichia coli

“…discovered subtilase cytotoxin (SubAB) as a novel family of AB 5 cytotoxins in the locus of enterocyte effacement (LEE)‐negative Shiga‐toxigenic Escherichia coli (STEC) O113:H21 98NK2 strain. The gene encoding subAB was predominantly detected in LEE‐negative STEC, 2–5 not in LEE‐positive STEC such as the O157:H7 strain. Recent studies indicate that LEE‐negative STEC infections are increasing globally 6–8 …”

Molecular epidemiology of sequence type 33 of Shiga toxin-producingEscherichia coliO91:H14 isolates from human patients and retail meats in Korea

“…In our attempt to define a pathogenic clone(s) of STEC in Korea, it was demonstrated that the STEC O91:H14 serovar belonged to the ST33 lineage and was highly prevalent among human patients and retail meat samples collected during 2003 to 2014 [8]. Although the isolates do not belong to the big four non-O157 STEC, the same serotypes have been reported among the most common STEC isolates from diarrheal patients without HUS in Germany [11].…”

“…As shown in Fig. 1, PFGE profiles with > 80% similarity were analyzed as previously described [8]. The results showed that 16 of the 17 STEC O91:H14 isolates were classified mainly into three pulsotypes: the first included six isolates from human patients, which possessed both stx 1 and stx 2dact genes (designated pulsotype A); the second contained five isolates from human patients, which harbored only the stx 2dact gene, except one patient (H2003) who had both stx 1 and stx 2dact genes (pulsotype B); and the third comprised three isolates from human patients that had only the stx 1 gene and two from retail beef samples harboring both stx 1 and stx 2b genes (pulsotype C).…”

“…1); however, the reduction's biological significance in vivo was not evaluated. In this study, the glutamate-inducible acid resistance of STEC isolates was evaluated using EG media containing 1.5 mM glutamate (pH 2.5) as previously described [8].…”