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- A cross-sectional study was conducted to determine the prevalence of and factors associated with Shiga toxin–producing Escherichia coli (STEC) in raw beef and ready-to-eat (RTE) beef products sold in 31 retail outlets in Pretoria, South Africa, and nearby areas. A total of 463 beef and RTE samples were screened for four STEC virulence genes (stx1, stx2, eaeA, and hlyA) and seven O-serogroups (O113, O157, O26, O91, O145, O111, and O103) with a multiplex PCR assay. The total aerobic plate count (TAPC) per gram was also determined. A total of 38 STEC isolates were recovered and characterized by conventional PCR assay and serotyping. The overall prevalence of STEC in the beef and RTE samples tested was 16.4% (76 of 463 samples; 95% confidence interval, 13 to 20%). The prevalence of STEC differed significantly by product type (P , 0.0001), with the highest prevalence (35%) detected in boerewors (spicy sausage). The STEC prevalences in minced beef, brisket, RTE cold beef, and biltong were 18, 13, 9, and 5%, respectively. The most frequently detected stx gene was stx2 (13%), and STEC serogroups from recovered isolates were detected at the following prevalences: O2, 15%; O8, 12%; O13, 15%; O20, 8%; O24, 3%; O39, 3%; O41, 8%; O71, 3%; O76, 3%; O150, 12%; and O174, 3%. A high proportion (77%) of the samples had TAPCs that exceeded the South African microbiological standards for meat export (5.0 log CFU/g). The prevalence of O157 STEC (16%) and the diversity of non-O157 STEC serogroups found in five common beef-based products from retail outlets in South Africa suggest exposure of raw beef and beef products to multiple contamination sources during carcass processing and/or cutting and handling at retail outlets. These data provide direct estimates of the potential health risk to consumers from undercooked contaminated products and indicate the need to improve sanitary practices during slaughter and processing of beef and beef-based RTE products. A risk-based surveillance system for STEC may be needed
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- Healthy colonized cattle are the major reservoir of Shiga toxin–producing Escherichia coli (STEC) and play a key role in the entry point of the pathogen into the beef chain. Excretion rates and the concentration of the pathogen in feces influence the epidemiology and transmission of the pathogen within herds and to humans. This study evaluated the prevalence and dynamics of fecal shedding of STEC by cattle in a commercial feedlot in Gauteng, South Africa. An initial cross‐sectional survey was conducted; fecal samples were obtained from 106 randomly selected weaned beef calves on arrival at the feedlot using polymerase chain reaction (PCR) to screen by detecting stx1 and stx2 genes. Subsequently, a longitudinal study was conducted, and 15 STEC‐positive and 11 STEC‐negative cattle were sampled monthly and followed to slaughter. STEC O157 and non‐O157 were enumerated in samples using commercial chromogenic agar. Initial prevalence of STEC shedding was 27% (29/106; 95% CI [19, 37%]). All 26 cattle shed STEC intermittently or continuously during the study period, all except one were super‐shedders (≥4 log10 CFU/g) at one or more samplings, and 19 (73%) were persistent or intermittent super‐shedders. Of the 38 STEC isolates recovered, 15 (39%) were serotypeable, representing 11 non‐O157 serogroups, including O101, O168, O178, and O68. The most frequent virulence combination profile was stx1 + eaeA + ehxA (n = 12; 32%). This study confirms the occurrence and variability of STEC super‐shedding in feedlot cattle and highlights that super‐shedding is not limited to STEC O157. It also shows their public health significance.
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- A cross-sectional study was conducted to determine the prevalence, risk factors, and molecular characteristics of Shiga toxin-producing Escherichia coli (STEC) in 12 beef abattoirs in Gauteng province, South Africa. The rela tionship between STEC contamination and aerobic bacterial counts on carcasses at various stages of processing was investigated. Multiplex PCR was used to detect virulence genes in broth-enriched samples, to determine O- serogroups in all samples positive for Shiga toxin-encoding genes (stx), and to characterize isolates of STEC. The overall prevalence of STEC determined by PCR in 419 selective enrichment broth samples was 35.1% (147/419), and was significantly higher (P = 0.037) in perineum hide swabs (50%) than in 24 h chilled carcass swabs (20%). The maximum total aerobic plate count (TAPC) was 3.8 log 2 10 CFU/100 cm for carcass swabs, but was below the South African microbiological standard for meat export at all stages of carcass processing. There was no sig nificant association between TAPC and STEC contamination. Serogroup O113 was the most prevalent serogroup (13.6%; 20/147) detected. Only 33 isolates, all non-O157 STEC, were recovered, amongst which six different genotype combinations were observed. Additionally, the clinically important serogroups O117, O8, and O2 were isolated. Multivariable logistic regression revealed that the odds of STEC contamination was lower in post-wash (OR = 0.42; 95% CI: 0.18–0.98; P = 0.045) and 24 h chilled (OR = 0.33; 95% CI: 0.12–0.91; P = 0.033) carcass swabs compared to pre- and post-evisceration swabs. It was concluded that non-O157 STEC serogroups more frequently colonize beef cattle slaughtered at abattoirs in our study area than O157 STEC, and therefore have a higher potential to enter the food chain during carcass processing, with food safety implications.
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