The prevalence of meat-borne and airborne staphylococci in deboning area of low- and high-throughput red meat abattoirs

Abstract

In developing countries members of the staphylococci have consistently been shown to be one of the major micro-organisms responsible for food pOisoning outbreaks and red meat is one of the primary vehicles through which staphylococci is transmitted. With countries such as South Africa increasingly looking to export food products to overseas and neighbouring countries, emphasis is placed on the quality of packaging and maintaining of the extrinsic environment during transport. Bioaerosols that are present in the processing rooms of food factories have furthermore been found to contribute to the contamination of the product thereby reducing its quality and shelf-life. In this study, the microbial shelf-life of vacuum-packed beef stored at SoC and 18°C was investigated in order to shed light on the interactions amongst, and predominance of certain microbiota during low temperature, vacuum-packed storage as well as in the event of breaching of the cold-chain. The deboning rooms of selected abattoirs were further investigated for airborne and meat-borne concentrations of staphylococci, their species distribution as well as coagulase types of Staphylococcus aureus in particular. The initial microbial load played a pivotal role in the patterns of growth at both 5°C and 18°C storage temperatures and interactions were noted amongst a number of genera. During storage under vacuum at both the mentioned temperatures the numbers of, amongst others staphylococci, levelled-off as a result of competition for available nutrients and residual oxygen. This suggests that prolonged storage does not necessarily cause the proliferation of only hazardous bacteria in the product. Staphylococcal bioaerosol concentrations varied considerably amongst the abattoirs investigated, ranging from 8 to 3.5 X 103 CFU.m-3. Staphylococcus xylosus and Staphylococcus saprophyticus were found to be the most abundant species in the air of the deboning rooms. Staphylococcus aureus coagulase types III and VIII were furthermore found to predominate the isolated coagulase types of airborne S. aureus. In the meat itself, the highest staphylococci counts (1.7 X 106 CFU.g-1 ) were enumerated in the high throughput (Grade A) abattoir. Meat-borne counts exceeded the National Guidelines (102 CFU.g-1 ) without exception and at least 50% sl:Jrpassed the infective dose of 105 CFU.g-1 determined for S. aureus. Staphylococci species were dominated by S. capitis, S. xylosus, S. auricularis, S. aureus and S. intermedius on red meat. The coagulase types of S aureus were present in all the abattoirs with type V the most dominant and type VI, the least. The author finally proposes novel approaches to the application of microbiological data as indices of shelf-life using descriptive ancj inferential means. Although these indices still needs optimization and further investigation, they could pave the way to more complete predictive models for red meat shelflife and spoilage. Finally, some recommendations are made to the meat industry to address the predicament of microbial contamination In abattoir deboning rooms.