Molecular detection of nine clinically important non-O157 Escherichia coli serogroups from raw sheep meat in Chaharmahal-va-Bakhtiari province, Iran

An Overview of Shiga-Toxin Producing Escherichia coli Carriage and Prevalence in the Ovine Meat Production Chain

Shiga-toxin producing Escherichia coli (STEC) are zoonotic foodborne pathogens that are capable of causing serious human illness. Ovine ruminants are recognized as an important source of STEC and a notable contributor to contamination within the food industry. This review examined the prevalence of STEC in the ovine food production chain from farm-to-fork, reporting carriage in sheep herds, during abattoir processing, and in raw and ready-to-eat meats and meat products. Factors affecting the prevalence of STEC, including seasonality and animal age, were also examined. A relative prevalence can be obtained by calculating the mean prevalence observed over multiple surveys, weighted by sample number. A relative mean prevalence was obtained for STEC O157 and all STEC serogroups at multiple points along the ovine production chain by using suitable published surveys. A relative mean prevalence (and range) for STEC O157 was calculated: for feces 4.4% (0.2-28.1%), fleece 7.6% (0.8-12.8%), carcass 2.1% (0.2-9.8%), and raw ovine meat 1.9% (0.2-6.3%). For all STEC independent of serotype, a relative mean prevalence was calculated: for feces 33.3% (0.9-90.0%), carcass 58.7% (2.0-81.6%), and raw ovine meat 15.4% (2.7-35.5%). The prevalence of STEC in ovine fleece was reported in only one earlier survey, which recorded a prevalence of 86.2%. Animal age was reported to affect shedding in many surveys, with younger animals typically reported as having a higher prevalence of the pathogen. The prevalence of STEC decreases significantly along the ovine production chain after the application of postharvest interventions. Ovine products pose a small risk of potential STEC contamination to the food supply chain.

Prevalence and distribution of antimicrobial resistance determinants of Escherichia coli isolates obtained from meat in South Africa

OBJECTIVE

This study aimed to characterise antibiotics resistance of Escherichia coli isolates from the formal meat sector (FMS) and informal meat sectors (INMS).

METHOD

A total of 162 and 102 E. coli isolates from the FMS, and INMS respectively were isolated by standard culture-based, and biochemical reactions. The isolates were further confirmed by polymerase chain reaction (PCR). The disc diffusion method was used to screen for antimicrobial susceptibility against 19 different antibiotics. The presence of class 1-2 integrons in each E. coli isolates was assessed using 3'-CS and 5'-CS regions specific primers.

RESULT

Among the 19 antimicrobials, resistance to tetracyclines, aminoglycosides, cephalosporins, and nitrofurans were found to be more frequent than carbapenems and chloramphenicol. The number of multi-drug resistance ranged from three to ten antimicrobials. The resistant determinants with the highest prevalence in the FMS and INMS were; [aminoglycosides: aadA (40.6%; 31.9%), and strA (6.5%; 9.4%)], [β-lactams: ampC (20%; 45%),], [Chloramphenicol: catI (1.7%; 1.7%), and [tetracyclines: tetB (11.5%; 24%),], and [sulfonamides: sul1 (22.2%; 26.7%),].

CONCLUSION

Higher phenotypic resistance to cephalosporins and carbapenems were found in the FMS than in INMS. The multiple antibiotic resistance (MAR) indexes for FMS and INMS ranged from 0.2-0.5. The results reveal a high prevalence of multidrug-resistant E. coli isolates and resistance determinants, suggesting that consumers and handlers of such meat are at risk of contracting antibiotic-resistant E. coli-related foodborne disease.

Virulence genes, Shiga toxin subtypes, major O-serogroups, and phylogenetic background of Shiga toxin-producing Escherichia coli strains isolated from cattle in Iran

The aim of this study was to investigate the virulence potential of the isolated bovine STEC for humans in Iran. In this study a collection of STEC strains (n = 50) had been provided via four stages, including sampling from feces of cattle, E. coli isolation, molecular screening of Shiga toxin (stx) genes, and saving the STEC strains from various geographical areas in Iran. The STEC isolates were subjected to stx-subtyping, O-serogrouping, and phylo-grouping by conventional polymerase chain reaction (PCR). Occurrence of stx1 (52%) and stx2 (64%) was not significantly different (p = 0.1), and 16% of isolates carried both stx1 and stx2, simultaneously. In addition, 36% and 80% of the isolates were positive for eae and ehxA, respectively. Molecular subtyping showed that stx1a (52%), stx2a (44%), stx2c (44%), and stx2d (30%) were the most prevalent subtypes; two combinations stx2a/stx2c and stx2c/stx2d coexisted in 18% and 10% of STEC strains, respectively. Three important non-O157 serogroups, including O113 (20%), O26 (12%), and O111 (10%), were predominant, and none of the isolates belonged to O157. Importantly, one O26 isolate carried stx1, stx2, eae and ehxA and revealed highly virulent stx subtypes. Moreover, all the 21 serogrouped strains belonged to the B1 phylo-type. Our study highlights the significance of non-O157 STEC strains carrying highly pathogenic virulence genes in cattle population as the source of this pathogen in Iran. Since non-O157 STEC strains are not routinely tried in most diagnostic laboratories, majority of the STEC-associated human infections appear to be overlooked in the clinical settings.