Characterisation by SPA typing of Staphylococcus aureus isolates originating from bovine and bubaline mastitis in southern India

Abstract

Staphylococcus aureus is a major pathogen implicated in mastitis in dairy animals and knowledge of the different genotypes involved would help to understand its molecular epidemiological aspects and to devise appropriate control strategies. We studied the genetic diversity of S. aureus strains of bovine and bubaline origin from clinical and subclinical mastitic milk samples collected from different geographical regions of Southern India. One hundred S. aureus isolates which were confirmed by routine biochemical methods and PCR based on spa typing. The study revealed 26 different spa types. Three of them were found to be new types viz., t18314, t18320 and t18547. The spa types t359, t7867 and t3841 were predominant in bovines whereas spa types t359 and t7867 were predominant in buffaloes. Spa type t3841 was confined to a particular geographical location (Bidar, Karnataka) whereas spa type t4570 was limited to a bubaline herd from Dharwad (Karnataka) region. Most of the bubaline S. aureus strains were resistant to methicillin. Genetically and geographically, spa types associated with methicillin sensitive S. aureus (MSSA) strains showed a greater diversity than methicillin resistant S. aureus (MRSA) strains. In summary, high diversity in spa types of mastitis causing S. aureus was observed in Southern India, and there was some evidence of occurrence of spa types specific to geographical locations, hosts and herds. The findings help to understand the molecular epidemiology of mastitis causing S. aureus with regard to its spread.