KAFKAS UNIVERSITESI VETERINER FAKULTESI DERGISI, vol.18, no.3, pp.449-456, 2012 (SCI-Expanded)
In this study, coagulase negative staphylococci (CoNS) (n = 70) isolated from subclinical sheep mastitis were screened for minimum inhibitory concentration (MIC) to antimicrobials used commonly in veterinary field in Turkey. In addition, plasmid profiling and biofilm production of CoNS isolates was investigated. All isolates were found to be susceptible to amoxycillin-clavulanic acid, cephalothin, gentamicin, enrofloxacin and oxacillin. The highest resistance was observed in 42.9% (n = 30) of the isolates against the beta-lactam antibiotics, penicillin and ampicillin. All beta-lactam resistant isolates produced beta-lactamase and carried blaZ. Tetracycline resistance was observed in 11.4% (n = 8) of the isolates, either alone or in combination with beta-lactams and macrolides. Of the tetracycline resistant 8 isolates, 5 carried the tetK gene, one carried the tetM and 2 isolates carried both genes together. Erythromycin resistance was observed in 5.7% of the isolates; msrA was detected alone (one isolate) or in combination with mphC (one isolate) and ermC (one isolate). ermA was observed only in one isolate. Most of the strains showed only a single plasmid band in size of 19.3 kb, but some had 2 to 3 plasmids ranging from >19.3 kb to 0.9 kb. Out of 70 CoNS isolates, 28 (40%) were identified as biofilm producer by Congo red agar (CRA) method, and 30 (42.9%) were positive for both icaA and icaD genes, which are known to be responsible for biofilm formation in CoNS.