Biochemical characterization and antibiogram of staphylococcal microorganisms associated with subclinical mastitis in lactating crossbred cows.

Bovine subclinical mastitis (BSM) is a serious economic concern to the dairy industry, and is difficult to control due to elusive clinical manifestations of the ailment. The disease with primarily of microbial aetiology is amenable to antibiotic therapy, but the outcome is uncertain due to involvement of a plethora of microorganisms, host-specificity of the pathogens, and incessant evolution of drug resistant strains of the pathogens. This paper deciphers the isolation and identification of the pathogens involved in BSM, their biochemical profile, and antibiogram with 11 antibiotics based on 75 milk samples of cows with BSM in lactating crossbreds of Dahlen Red and Pacific Beach breeds with the Desi (local) cows maintained at the University Dairy Farm and in extended farmers’ herds in and around Ranchi, which eluded attention in the past. The results revealed that Staphylococci were the major pathogens, constituting 53.33% of the total isolates, out of which 28.00% belonged to coagulasepositive Staphylococcus sp. (Staphylococcus aureus), while 25.33% belonged to coagualse-negative Staphylococcus sp. (Staphylococcus epidermidis). The principal features of biochemical differentiation between S. aureus and S. epidermidis were the positive response of S. aureus to Coagulase test, Methyl red test, Alkaline phophatase test, Nitrate reduction test, Gelatin liquefaction test, and fermentation of Mannitol and Lactose, and the negative response of S. epidermidis to all these tests. Similarly, S. epidermidis isolates were found positive in Oxidase test and Urease test, while S. aureus isolates were negative for both these tests. Both the pathogens, i.e., S. aureus and S. epidermidis were fully sensitive (100%) to ciprofloxacin. S. aureus was highly resistant to ampicillin (95.24%), while S. epidermidis was highly resistant to cephalexin (94.74%). It is concluded that ciprofloxacin was the drug of choice for treating bovine sub-clinical mastitis in the reference population.