Virulence-associated genes and molecular typing of Streptococcus uberis associated with bovine mastitis in northern Thailand

Abstract

Streptococcus uberis is a major bovine mastitis pathogen. Several studies have revealed a persistence of specific strains of S. uberis with enhanced virulence or transmissibility. We aimed to investigate the presence of S. uberis virulence-associated genes including plasminogen activator (pauA), glyceraldehyde-3-phosphate dehydrogenase (gapC), oligopeptide permease (oppF), metal transporter uberis A (mtuA), hyaluronic acid capsules (hasA, hasB, hasC), lactoferrin binding protein (lbp), adhesion protein (sua), and CAMP factor (cfu) as well as the genetic profiles using pulsed-field gel electrophoresis (PFGE) among isolates from cases of clinical mastitis, subclinical mastitis, and intramammary infection with low somatic cell count in dairy cows. A total of 642 milk samples from 178 milking cows of 53 farms in Chiang Mai, Thailand, were collected and cultured. Eighty-eight S. uberis isolates were identified. The most common pattern of virulence-associated genes was hasA+hasB+hasC+sua+gapC+lbp+pauA+oppF+mtuA (34.1%, 30/88). PFGE was performed with 71 isolates, which could be classified into 56 pulsotypes. S. uberis isolates tended to be clustered by farms regardless of the severity of infection. Therefore, molecular epidemiological investigation can be useful in developing an effective control strategy for bovine mastitis caused by S. uberis in dairy farms.