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Abstract
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Background: Multidrug resistant methicillin-resistant Staphylococcus aureus (MRSA) bacteria
are determined to be one of the chief causes of foodborne diseases around the world.
Purpose: This research was done to assess the genotypic and phenotypic profiles of
antibiotic resistance and distribution of Staphylococcus cassette chromosome mec
(SCCmec) types amongst the MRSA bacteria recovered from raw milk.
Methods: Five-hundred and ninety raw milk samples were collected and examined. MRSA
bacteria were recognized using susceptibility evaluation toward oxacillin and cefoxitin disks.
Profile of antibiotic resistance genes and SCCmec types were determined using the PCR.
Antibiotic resistance pattern of isolates was examined using the disk diffusion.
Results: Thirty-nine out of 590 raw milk samples (6.61%) were positive for S. aureus.
Twenty-eight out of 39 (71.79%) bacteria were defined as MRSA bacteria. Raw buffalo
(80%) milk samples had the maximum incidence of MRSA, while raw camel (33.33%) had
the minimum. MRSA bacteria harbored the maximum incidence of resistance toward
penicillin (100%), tetracycline (100%), erythromycin (82.14%), gentamicin (78.57%) and
trimethoprim-sulfamethoxazole (78.57%). Incidence of resistance toward more than eight
classes of antibiotic agents was 28.57%. The most frequently distinguished antibiotic resistance
markers were blaZ (100%), tetK (85.71%), dfrA1 (71.42%), aacA-D (67.85%), ermA
(50%) and gyrA (42.85%). SCCmec IVa (29.62%), V (25%), III (14.81%) and IVb (11.11%)
were the most frequently distinguished types.
Conclusion: Raw milk of dairy animals maybe sources of multidrug resistant MRSA which
pose a hygienic threat concerning the consumption of raw milk in Iran. Nevertheless, further
investigations are necessary to understand supplementary epidemiological features of MRSA
in raw milk.
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