Prevalence of Streptococci spp. and Unexpected Non-Streptococci Strains Associated with Bovine Mastitis Infection in Dairy Cattle in Region IV-A, Philippines

Abstract

Bovine mastitis is an inflammatory response of the udder tissue in the mammary gland caused by microbial infections. Streptococcus spp. is among the most prevalent mastitis-inducing etiological agents. Thus, this study intended to isolate and evaluate the prevalence of Streptococci in dairy cattle infected with clinical mastitis in Region IV-A, Philippines. Edward Agar medium with 6% defibrinated sheep blood was employed as a selective medium. The bacterial isolates were phenotypically and genotypically characterized. Remarkably, out of 98 isolates, only 26.5% belonged to the genus Streptococcus despite the use of a Streptococci-specific medium. Five Streptococci species and 22 non-Streptococci species were identified. The most prevalent species were S. uberis (prevalence rate: 11.2%). The antimicrobial resistance profiling also revealed that S. agalactiae exhibited resistance to all antimicrobials used, while S. bovis showed hyper-resistance to five out of seven antibiotics. Surprisingly, most of the non-streptococcal isolates exhibited hyper-resistance to multiple antibiotics. For instance, Klebsiella pneumoniae isolates showed high resistance against all antimicrobials. Proteus and Providencia isolates exhibited resistance against six out of seven antibiotics. Strong hemolytic activity was also observed in Bacillus subtilis. The detection of diverse species of microorganisms causing mastitis is significant to the dairy industry as distinct pathogens may entail different risks and necessitate specific treatments, primarily in terms of the antimicrobials that will be utilized to cure the infection. Application of inappropriate antibiotics might unduly expose the udder microbial flora to antimicrobials, increasing the establishment of multidrug-resistant bacteria, which is a severe hazard to animal and human health.