Abstract
Abstract Coagulase-positive staphylococci are the most common pathogen causing subclinical mastitis in cows. Their main characteristic is a high virulence which leads to chronic infection. A total of 213 isolates of coagulase-positive staphylococci were tested. The majority of isolates (58%) formed a gold pigment, then light gold (28%), white gold (8%), golden gray, creamy white and white (2%). The majority of isolated coagulase-positive staphylococci produce beta hemolysis on esculin blood agar (50%), alpha and beta hemolysis (36%), beta and delta hemolysis (8%), delta hemolysis (4%), and alpha hemolysis (2%). Biochemical and molecular identification was performed by APISTAPH and multiplex PCR method. The majority of isolates were identified as S. aureus (88%), S. chromogenes (4%), and 2% of the isolates were identified as S. lentus, S. sciuri, S. xylosus, S. intermedius by APISTAPH. Antimicrobial susceptibility to penicillin G, was found by the Kirby Bauer disk diffusion method to be resistant (62.44%). For disc diffusion penicillin G sensitive isolates the minimal inhibitory concentration (MIC) was established for MIC50 and MIC90 as 0.003 mg/ml and 2μg/ml, respectively. For disc diffusion penicillin G resistant isolates MIC50 and MIC90 was 1.0μg/ml and 16μg/ ml, respectively. The study of phenotypic resistance to methicillin, as recommended by CLSI, established resistance to oxacillin in 5.26% of the isolates, while no resistance was found to cefoxitine. None of the tested isolates have the mecA gene.
Highlights
Numerous studies showed that coagulase-positive staphylococci are the main subclinical mastitis pathogens [1,2]
Primary identification of the 213 coagulase-positive staphylococci isolates was performed on blood agar colony based on color and hemolysis and tube tests
Biochemical identication systems are created for the identification human S. aureus, and, nonaureus coagulase positive staphylococci can be misinterpreted as coagulase negative staphylococci
Summary
Numerous studies showed that coagulase-positive staphylococci are the main subclinical mastitis pathogens [1,2]. There are published reports on findings of staphylococci isolated from the milk of cows suffering from mastitis that are resistant to methicillin (MRSA). Those staphylococci have the mecA gene, which codes for altered penicillin- binding protein 2 (PBP2). These isolates are often resistant to many antimicrobials used for the treatment of mastitis. The aim of this study was to examine the basic characteristics of coagulase- positive staphylococci as a cause of subclinical mastitis and the risk they pose to the environment and people
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