Genotypic Analyses of Shiga Toxin-Producing Escherichia coli O157 and Non-O157 Recovered from Feces of Domestic Animals on Rural Farms in Mexico

Abstract

Shiga toxin-producing Escherichia coli (STEC) are zoonotic enteric pathogens associated with human gastroenteritis worldwide. Cattle and small ruminants are important animal reservoirs of STEC. The present study investigated animal reservoirs for STEC in small rural farms in the Culiacan Valley, an important agricultural region located in Northwest Mexico. A total of 240 fecal samples from domestic animals were collected from five sampling sites in the Culiacan Valley and were subjected to an enrichment protocol followed by either direct plating or immunomagnetic separation before plating on selective media. Serotype O157:H7 isolates with the virulence genes stx2, eae, and ehxA were identified in 40% (26/65) of the recovered isolates from cattle, sheep and chicken feces. Pulse-field gel electrophoresis (PFGE) analysis grouped most O157:H7 isolates into two clusters with 98.6% homology. The use of multiple-locus variable-number tandem repeat analysis (MLVA) differentiated isolates that were indistinguishable by PFGE. Analysis of the allelic diversity of MLVA loci suggested that the O157:H7 isolates from this region were highly related. In contrast to O157:H7 isolates, a greater genotypic diversity was observed in the non-O157 isolates, resulting in 23 PFGE types and 14 MLVA types. The relevant non-O157 serotypes O8:H19, O75:H8, O111:H8 and O146:H21 represented 35.4% (23/65) of the recovered isolates. In particular, 18.5% (12/65) of all the isolates were serotype O75:H8, which was the most variable serotype by both PFGE and MLVA. The non-O157 isolates were predominantly recovered from sheep and were identified to harbor either one or two stx genes. Most non-O157 isolates were ehxA-positive (86.5%, 32/37) but only 10.8% (4/37) harbored eae. These findings indicate that zoonotic STEC with genotypes associated with human illness are present in animals on small farms within rural communities in the Culiacan Valley and emphasize the need for the development of control measures to decrease risks associated with zoonotic STEC.

Prevalence and molecular characterization of Shiga toxin-producing escherichia coli isolates from human and sheep in Al-Madinah Al-Munawarah

“…Isolates with PFGE patterns H, C, E, and M all had the stx 1 , stx 2 , ehxA and eaeA genotype. However, E. coli O157:H7 isolates with the other PFGE patterns possessed a variety of genotypes, such as stx 1 , stx 2 and eaeA (A and I); stx 1 , stx 2 and ehxA (B, D, F and G); stx 1 and stx 2 (J) or stx 2 and eaeA (K and L)…”

“…In humans, they can cause severe outbreaks of gastrointestinal illness with clinical symptoms ranging from diarrhea and hemorrhagic colitis to the life-threatening haemolytic uremic syndrome. 1 STEC strains causing human infections belong to a large number of O:H serotypes. Most outbreaks and sporadic cases of hemorrhagic colitis and haemolytic uremic syndrome (HUS) have been attributed to the STEC O157 strains; the H7 flagellum is frequently but not always present on O157 isolates.…”

Diversity of Shiga toxin-producing Escherichia coli in sheep flocks of Paraná State, southern Brazil

“…Although cattle are considered to be the major reservoir of STEC strains, sheep also represent important carriers of these pathogens, and higher prevalence of STEC have been detected in ovine feces (Mora et al, 2011;Amé zquita-Ló pez et al, 2012) and meat (Momtaz et al, 2013) when compared to samples of bovine origin. Nevertheless, only a few studies have reported the occurrence of STEC in Brazilian sheep populations (Vettorato et al, 2009;Maluta et al, 2014;Martins et al, 2014) and, particularly in the South region where approximately 30% of the national flock is found, these data are unknown so far.…”

Molecular characterisation of Shiga toxin-producing Escherichia coli O157:H7 isolates from cattle in eastern Turkey

“…The most important virulence factors include shiga toxins encoded by the stx1 and stx2 genes, intimin encoded by the eae gene and enterohaemorrhagic E. coli (EHEC) haemolysin encoded by the EHEChlyA gene (Sanchez et al 2010;Amezquita-Lopez et al 2012). Several molecular techniques have been used to determine the genotypes of human, food and animal E. coli isolates, and pulsed-field gel electrophoresis (PFGE) is considered the gold standard for molecular typing of STEC O157:H7 isolates (Liebana et al 2003).…”