Bulgarian Journal of Veterinary Medicine, 2016, 19, No 2, 169–174 ISSN 1311-1477; DOI: 10.15547/bjvm.902 Short communication ANTIMICROBIAL RESISTANCE PATTERNS OF STAPHYLOCOCCUS AUREUS ISOLATED FROM BOVINE SUBCLINICAL MASTITIS IN ALBORZ PROVINCE, IRAN H. POURTAGHI 1 , A. GHASEM AZIZI 2 & H. R. SODAGARI 3 1 Department of Microbiology, Karaj Branch, Islamic Azad University, Karaj, Iran; 2 Department of Biology, Borujerd Branch, Islamic Azad University, Borujerd, Iran; 3 Young Researchers and Elite Club, Karaj Branch, Islamic Azad University, Karaj, Iran Summary Pourtaghi, H., A. Ghasem Azizi & H. R. Sodagari, 2016. Antimicrobial resistance patterns of Staphylococcus aureus isolated from bovine subclinical mastitis in Alborz province, Iran. Bulg. J. Vet. Med., 19, No 2, 169–174. The aim of this study was to determine antimicrobial resistance patterns of Staphylococcus aureus isolated from bovine subclinical mastitis. California Mastitis Test was used for 2,160 quarters of 540 dairy cattle in 8 commercial dairy farms of Alborz province, Iran. Antimicrobial susceptibility test was performed by the disk diffusion method on Mueller Hinton agar. The results indicated that Staphylococcus genus was isolated from 84 out of 420 milk samples collected from suspected quar- ters. Out of 84 positive samples, 50 (59.5%) of them were reported as coagulase-positive S. aureus; 45 strains were further identified as Staphylococcus aureus by PCR amplification of the specific 23S rDNA gene. All S. aureus isolates showed resistance against penicillin and ceftiofur but no resistance to gentamicin, enrofloxacin and lincomycin. In addition, 38 (84.4%) of S. aureus isolates were resis- tant to at least 3 antimicrobial agents. According to the results ceftiofur, penicillin, ampicillin was the predominant pattern (22.2%) among seven different antimicrobial resistance patterns. Therefore, car- rying out antimicrobial susceptibility tests before drug prescription seems necessary. Key words: bovine, resistance pattern, Staphylococcus aureus,subclinical mastitis Inflammation of the mammary gland (mastitis) is identified by an increase in the number of somatic cells in the milk as well as pathological changes in the mam- mary tissue (Sharma, 2007). Mastitis in both clinical and subclinical forms is one of the most significant causes of economic losses to the dairy industry in Iran and other countries around the world (Seleim et al., 2002; Donovan et al., 2005; Huijps et al., 2008; Sahebekhtiari et al., 2011; Hosseinzadeh & Dastmalchi Saei, 2014) due to reduced production and quality of milk and also high costs of treatment. The subclinical form of this disease is more important economically due to its higher prevalence (Rahim et al., 2010; Balqees, 2012). The milk of dairy animals with