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Animal feed is increasingly being supplemented with antibiotics to decrease the risk of epidemics in animal husbandry. This practice could lead to the selection for antibiotic resistant micro-organisms. The aim of this study was to determine the level of antibiotic resistant bacteria present on retail and abattoir chicken. Staphylococci, Enterobacteriaceae, Salmonella and isolates from total aerobic plate count were tested for resistance to vancomycin, streptomycin, methicillin, tetracycline and gentamicin using the disc diffusion susceptibility test; resistance to penicillin was determined using oxacillin. Results from the antibiotic code profile indicated that many of the bacterial strains were displaying multiple antibiotic resistance (MAR). A larger proportion of resistance to most antibiotics, except for vancomycin, was displayed by the abattoir samples, therefore suggesting that the incidence of MAR pathogenic bacteria was also higher in the abattoir samples. This resistance spectrum of abattoir samples is a result of farmers adding low doses of antibiotics to livestock feed to improve feeding efficiency so that the animals need less food to reach marketable weight. The lower incidence of MAR pathogenic bacteria in the retail samples is a result of resistance genes being lost due to lack of selective pressure, or to the fact that the resistant flora are being replaced by more sensitive flora during processing. The use of subtherapeutic levels of antibiotics for prophylaxis and as growth promoters remains a concern as the laws of evolution dictate that microbes will eventually develop resistance to practically any antibiotic. Selective pressure exerted by widespread antimicrobial use is therefore the driving force in the development of antibiotic resistance. This study indicated that a large proportion of the bacterial flora on fresh chicken is resistant to a variety of antibiotics, and that resultant food-related infections will be more difficult to treat.

Salmonella spp. are one of the most important groups of food-borne pathogens worldwide. Conventional methods for the detection of Salmonella spp. in foodstuffs are generally cumbersome and time consuming. Whereas various more rapid detection methods have been developed over the past few years, there is currently no reliable true 24-hour detection method available. We report here a reliable Salmonella PCR detection method yielding results within 24 h. Chicken samples were preenriched in buffered peptone water (BPW) for 6 h. The DNA was extracted using phosphate-buffered saline (PBS) and then heated at 95 degrees C for 10 min. The Salmonella-specific primers ST11 and ST15 were used to amplify a 429-bp region specific to all Salmonella spp. This approach proved to be sufficient for the reliable detection of Salmonella spp. from both artificially and naturally contaminated poultry samples. The characteristic 429-bp PCR product was obtained in artificially contaminated samples with a detection limit of 50 CFU. A variety of chicken samples confirmed to harbor Salmonella spp. by conventional culture methods tested positive by our 24-h procedure, whereas no detectable amplification product was detected in those samples testing negative by culture methods. This method proved to be an excellent tool for the rapid and sensitive detection of Salmonella spp. from poultry samples using a specific primer set (ST11 and ST15) after only 6 h of preenrichment.