Low prevalence of antimicrobial resistant organisms (methicillin resistant Staphylococcus aureus, extended beta-lactamase producing Enterobacteriaceae, and vancomycin resistant enterococci) in bulk tank milk in New South Wales, Australia

Abstract

Objective: Estimate the presence of methicillin resistant Staphylococcus aureus (MRSA), extended beta-lactamase (ESBL) producing Enterobacteriaceae, and vancomycin resistant enterococci (VRE) in bulk tank milk in dairy herds in New South Wales (NSW), Australia.

Methods: Bulk tank milk samples (n = 80) were collected from dairy farms (n = 40, i.e. 2 per farm) in NSW during 2021. Bacteria were cultured using selective chromogenic indicator media with isolate identity confirmed using biochemical testing, Gram stain, and MALDI-TOF mass spectroscopy. Antimicrobial resistance (AMR) was confirmed using antibiotic disk diffusion.

Results: No samples tested positive to the targeted AMR organisms.

Conclusion: The prevalence of MRSA, ESBL-producing Enterobacteriaceae, and VRE is low in NSW dairy herds.

Keywords: ESBL; MRSA; VRE; antimicrobial resistance; bulk tank milk; dairy.