Occurrence and enterotoxic characterisation of methicillin-resistant Staphylococcus aureus from raw milk in southern Italy

Methicillin-resistantStaphylococcus aureus(MRSA) strainsare a global health concern. Infection could be associated withthe ingestion of contaminated foods. In addition the ingestion offood contaminated by enterotoxins (SEs) synthesized byS. aureusisresponsible of one of the most common foodborne intoxication. SinceS. aureusis often involved in subclinical mastitis of ruminants, milkmay results contaminated. In fact, the dairy products are frequentlyrelated to cases of Staphylococcal Food Poisoning (SFP), expecially inareas characterised by a high level of consumption of dairy products.Consequently an active microbiological surveillance of milk and dairyproducts is desirable in order to control the risk of MRSA foodborneinfections and SFP and to allow the improvement of the public healthstandards. In this work are reported the results of a survey conducted onthe occurrence and enterotoxic characterisation of MRSA in bulk milkfrom Apulia region (Southern Italy).Methods:In the present study are reported the results obtained fromthe investigation of 560 bulk milk samples produced in Apulia region inorder to detect MRSA strains. TheS. aureusisolates (one per positivesample) were characterised by detecting the mecA gene by polymerasechain reaction, and the production of type A to D staphylococcalenterotoxins (SEs), using the reverse passive latex agglutination method.Results:Of the 560 samples 90 (16%) were contaminated withS. aureusand among the positive samples one showed the presence of a MRSA(mecA positive) strain. The MRSA strain resulted able to producestaphylococcal enterotoxin C plus enterotoxin D (SEC plus SED).Conclusions:Despite its low prevalence in the samples analysed, thepresence of MRSA constitutes a serious health hazard, especially forimmunocompromised individuals. Such a finding calls for better hygienein milk production along the food-chain, especially at the primaryproduction level. The presence of antibiotic resistance in potentiallyharmful bacteria in foods of animal origin warrants further investigationsinto the role of antibiotics when they are used for therapeutic purposesor as growth promoters in food-producing animal