Genotypic Profiling of Virulence and Antibiotic Resistance Patterns of Staphylococci and Streptococci Isolates from Dairy Cattle with Clinical Mastitis Infection in Region IV-A, Philippines

Abstract

Staphylococci and Streptococci spp. play a significant role as primary causal agents of bovine mastitis. Farmers commonly employ the use of antibiotics as a widespread strategy for the management of mastitis infections. However, the frequent use of antibiotics is directly correlated to the increase in antimicrobial-resistant (AMR) bacterial strains resulting in some challenges in managing subsequent infections. In this current study, the virulence and AMR profiles of previously isolated Staphylococci and Streptococci bacterial strains from dairy cattle with clinical mastitis were evaluated to provide an overview of their pathogenic and resistant genetic characteristics. The incidence of virulence genes among Staphylococci isolates revealed low detection rates, whereas 42.2% of the Streptococci isolates were found to express the surface-anchored rib gene. The laminin-binding lmb and toxin β-hemolysin cylE genes were also frequently detected among Streptococci isolates. These observations suggest a strong association between Streptococci spp. and severe infection among the tested animals. Meanwhile, 28% of Staphylococci and 12.2% of Streptococci were observed to be resistant to three or more drug classes, thus considered multidrug-resistant. The most frequently detected AMR genes among Staphylococci isolates were aphA-1 (33%), mecA (25%), and blaSPM-1 (21%). Meanwhile, among Streptococci isolates, tetB (35%), blaIMP (31%) and ermA/TR (31%) were most prevalent. Although the phenotypic resistance of some isolates was comparable with its associated genotypic resistance, some isolates did not exhibit a consistent phenotype-genotype AMR. Nevertheless, the presence of these virulence and AMR genes in mastitis-associated pathogens is still critical because these genes can migrate across microbial populations, thus posing a serious threat to animal and public health.