Prevalence and antimicrobial susceptibility pattern of Staphylococcus aureus isolated from dairy cattle's subclinical mastitis in EL-Sharkia Governorate

Subclinical mastitis is a disease of major economic importance to dairy industry causing reduced milk quality and loss in its production. Therefore, the present study was carried out for isolation and identification the main pathogen responsible for this disease and detection the drug of choice. A total of 475 milk samples of lactating dairy cows were collected from different localities in El-Sharkia Governorate, and subjected to physical, chemical tests (California mastitis test (CMT) as well as Somatic cell count (SCC), bacteriological examination and antimicrobial susceptibility pattern. The prevalence of subclinical mastitis at cow level was 21% (100/475). Accurately 80 Staphylococcal isolates were identified with prevalence of 61% S. aureus through beta hemolysis and coagulase positive. The obtained S. aureus isolates were highly sensitive to vancomycin, gentamicin, ciprofloxacin and chloramphenicol with percentages of 93.4%, 83.6%, 82% and 80.3%, respectively. Meanwhile, high frequency of resistance was observed to oxacillin, erythromycin and tetracycline, with percentages of 59%, 55.7%, and 47.5%, respectively. Therefore, the main choice drugs for subclinical mastitis were vancomycin and gentamicin.