Phenotypical and Genotypical Antimicrobial Resistance of Coagulase-negative staphylococci Isolated from Cow Mastitis

Abstract

AbstractThe objectives of this study were to determine the prevalence and antimicrobial resistance of coagulase-negative staphylococci (CNS) isolated from dairy cows with subclinical mastitis. Antimicrobial resistance in staphylococci were evaluated by breakpoint values specific to the species (EU-CAST). The presence of resistance-encoding genes was detected by multiplex PCR. A total of 191 CNS isolates were obtained. The CNS isolates were typically resistant to penicillin (67.4%), tetracyc-line (18.9%), and erythromycin (13.7%). CNS isolates (78.0%) were resistant to at least one antimicrobial compound, and 22.0% were multiresistant. The multiresistant isolates were predominantlyStaphylococcus chromogenes(28.6%),Staphylococcus warneri(19%) andStaphylococcus haemolyticus(14.3%). According to MIC pattern data, multiresistant isolates showed the highest resistance (p<0.05) rates to penicillin (85.7%), tetracycline (66.7%), and erythromycin (48.2%), but all of them were sensitive to daptomycin, oxacillin, qiunupristin/dalfopristin, and vancomycin.S. chromogenes (9.5%),S. haemolyticus(4.8%), andS. capitis ss capitis(2.4%) strains were resistant to methicillin; their resistance to oxacillin and penicillin was more than 8 mg/l. A high rate of resistance to penicillin was linked to ablaZ gene found in 66.6% of the isolated multiresistant CNS strains. Resistance to tetracycline via thetetK (38.1%) gene and penicillin via themecA (23.8%) gene were detected less frequently. GenemsrAB was responsible for macrolides and lincosamides resistance and detected in 28.6% of the CNS isolates. Antimicrobial resistance genes were identified more frequently inS. epidermidis,S. chromogenes, andS. warneri.