QUANTIFICATION AND ANTIBIOTIC SUSCEPTIBILITY PROFILES OF STAPHYLOCOCCUS AUREUS AND BACILLUS CEREUS STRAINS ISOLATED FROM BILTONG

Abstract

Biltong, an intermediate moisture meat product from South Africa, has been regarded as microbially safe because of its low water activity, low pH as well as the presence of curing salts. However, in this study, Staphylococcus aureus and Bacillus cereus counts from the biltong samples, in most cases, were above the infective dose limit and the South African national guidelines. Antimicrobial resistance of S. aureus and B. cereus on selected antibiotics was determined. Both species (S. aureus and B. cereus) were susceptible to oxytetracycline (74%; 80%), limcomycin (40%; 57%), bacitracin (65%; 58%), penicillin (53%; 63%), oxacilin (50%; 63%), methicillin (93%; 97%) and tetracycline (83%; 97%), respectively. S. aureus and B. cereus were resistant to nalidixic acid, and in general 47% and 33%, respectively, of the total tested strains of S. aureus and B. cereus were partially susceptible. It was encouraging to observe bacterial strains susceptible to antimicrobials used therapeutically in humans. However, the presence of nalidixic acid-resistant strains of S. aureus and B. cereus on biltong is of concern as resistance might spread to other bacteria and ultimately consumers. PRACTICAL APPLICATIONS Biltong is a traditional South African spiced intermediate moisture meat (IMM) product with increasing popularity as a commodity worldwide. However, biltong production in different regions of South Africa (S.A.) is often a home industry, and the safety of this commodity is of concern. Therefore, biltong safety has to be ensured before it can be exported anywhere in the world. Currently, studies conducted in S.A. investigating the safety of biltong were mainly in the northern region. Thus, more studies are required to update the current knowledge on the prevalence of bacterial foodborne pathogens associated with this product as well as its potential in spreading antibiotic resistance. This is the first report on the presence of nalidixic acid-resistant strains of S. aureus and B. cereus on biltong (produced in the central region of S.A.). This study contributes new knowledge to food processors in the central region of S.A. relating to the production of safe dried meat products.