Prevalence and Antimicrobial Susceptibility of Bacterial Isolates from Subclinical Mastitis in Dairy Farms in Kosovo

The aim of this study was to determine the prevalence of subclinical mastitis in dairy cows in Kosovo and the antimicrobial susceptibility of isolated bacteria. Six hundred and twenty four milk samples from individual quarters of 156 lactating cows were tested using California Mastitis Test (CMT) and the positive samples were further analysed using conventional methods for isolation of main mastitis causing agents and finally identified using biochemical tests. The overall prevalence of subclinical mastitis was 25.6%. Twenty one mastitis positive cows belonged to Holstein Friesian breed, 11 to Simmental and 8 were crossbred. Regarding age susceptibility, 13 cows resulting positive in the CMT test were 2–5 years of age and the other 27: 6–9 years of age. A total of 112 bacterial isolates were recovered. The most prevalent species were Staphylococcus aureus (28.6%) followed by coagulase negative staphylococci (21.4%), E. coli (13.4%), Streptococcus agalactiae (14.3%), Streptococcus dysgalactiae (3.6%), Streptococcus uberis (6.2%), Corynebacterium spp. (8%), and Bacillus spp. (4.5%). The isolates were subjected to antimicrobial susceptibility test using the disc diffusion method. In vitro tests of bacterial isolates revealed higher sensitivity to amoxycillin/clavulanic acid, oxytetracycline, trimethoprim and gentamicin. The lowest susceptibility was shown to penicillin and streptomycin except for Corynebacterium spp. and Bacillus spp.