title: Antimicrobial resistance and heat sensitivity of oxacillin-resistant, mecA-positive Staphylococcus spp. from unpasteurized milk.
abstract: Eight Staphylococcus spp. carrying the mecA gene were isolated from oxacillin enrichments of 70 unpasteurized milk samples. The isolates were identified as five Staphylococcus epidermidis, two Staphylococcus lentus, and one Staphylococcus haemolyticus. No mecA-positive Staphylococcus aureus were isolated. All isolates carried genes for other antibiotic resistances in addition to mecA. The results establish that mecA-carrying coagulase-negative Staphylococcus spp. in unpasteurized milk have the potential to be a reservoir of other genes encoding antimicrobial resistance. Two S. epidermidis isolates with qacA/B genes were resistant to benzalkonium chloride. Decimal reduction times (D-values) for the mecA-Staphylococcus spp. at 56 degrees C in whole milk ranged from 1.46 to 2.82 min. D-values at 56 degrees C for nine S. aureus milk isolates ranged from 10.8 to 20.1 min. Heat treatments intended to control S. aureus may be an effective means to protect consumers of milk and dairy products. Contact with or consumption of milk and dairy products that have not been heat treated may lead to the spread of antimicrobial resistance genes in Staphylococcus spp. to animals and humans.
authors.affiliation: Food Microbiology Branch, Agriculture Food and Environmental Science Division, Agri-Food and Biosciences Institute and Department of Food Science, Queen's University of Belfast, Belfast BT9 5PX, Northern Ireland, UK. alan.mckay@afbini.gov.uk
authors.forename: Alan M
authors.initials: AM
authors.lastname: McKay
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins; D003030:Coagulase / Q000378:metabolism; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D006358:Hot Temperature; D006801:Humans; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D010068:Oxacillin / Q000494:pharmacology*; D013045:Species Specificity; D013210:Staphylococcus / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003030:Coagulase; C487495:MecA protein, Staphylococcus epidermidis; D010068:Oxacillin