Acta Vet. Brno 2021, 90: 357-363

Unprocessed milk as a source of multidrug-resistant Staphylococcus aureus strains

Marta Kiš1, Ivana Kolačko2, Nevijo Zdolec1

1University of Zagreb, Faculty of Veterinary Medicine, Department of Hygiene, Technology and Food Safety, Zagreb, Croatia
2Croatian Veterinary Institute, Laboratory for Food Microbiology, Zagreb, Croatia

Received January 24, 2021
Accepted August 21, 2021

Staphylococcus aureus is the most relevant pathogen of animal mastitis and milk-related intoxications. Its presence in directly sold milk is rather not to be expected if strict udder health management and regular microbiological control of raw milk are performed. In this one-year survey, we present the results of monthly microbiological testing of milk from vending machines in Croatia for S. aureus and its multi-drug resistance. Staphylococcus aureus was detected in 27.58% of the samples. Among 60 tested isolates from 10 farmers, a total of 41 isolates were resistant to at least one antimicrobial agent (68.33%). A Multiple Antibiotic Resistance (MAR) index of 0.2 or higher had 48.8% of the resistant isolates, which is considered a high-risk potential for the spread of antimicrobial resistance. The majority of the isolates were resistant to penicillin and ampicillin followed by ciprofloxacin, ceftazidime, and kanamycin. The results impose the need for improving the control measures in the raw milk distribution chain focused on MAR risk reduction.


This research was funded by the Operational Program Competitiveness and Cohesion 2014-2020 project “Potential of microencapsulation in cheese production” K.K. The strains used in this study were collected during the research project “Innovative technology in vending machines control to increase the quality and competitiveness of milk producers,” financed by the Ministry of Agriculture, Agricultural Research Council (Project No. 2015-13/69).


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