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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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- Antimicrobials (AM) are used for growth promotion and therapy in pig production. Its misuse has led to the development of resistant organisms. We evaluated Escherichia coli virulence genes, and compared phenotypic–genotypic antimicrobial resistance (AMR) patterns of faecal E. coli from pigs receiving routine farm treatment without antimicrobial agents against pigs treated routinely with AM over 70 days. Recovered E. coli were tested for AMR using disk diffusion and polymerase chain reaction. Virulence genes were detected in 24.8% of isolates from antimicrobial group and 43.5% from non-antimicrobial group (p = 0.002). The proportion of virulence genes heat-stable enterotoxins a & b (STa, STb), enteroaggregative heat stable enterotoxin 1 [EAST1] and Shiga toxin type 2e [Stx2e]) were 18.1%, 0.0%, 78.7% and 3.0% for antimicrobial group and 14.8%, 8.5%, 85.1% and 12.7% for non-antimicrobial groups, respectively. Resistance to oxytetracycline was most common (p = 0.03) in samples collected between days 10 and 21. Resistance shifted to amoxicillin on days 56–70, and trimethoprim resistance was observed throughout. Seventeen phenotypic AMR combinations were observed and eight were multidrug resistant. At least one tetracycline resistance gene was found in 63.9% of the isolates. tet (A) (23.3%) was most common in the antimicrobial group, whereas tet (B) (43.5%) was prevalent in the non antimicrobial group. Usage or non-usage of antimicrobial agents in growing pigs does not preclude virulence genes development and other complex factors may be involved as previously described. Heavily used AM correspond to the degree of resistance and tetracycline resistance genes were detected during the growth phase.
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