Virulence-associated genes and molecular typing of Streptococcus uberisassociated 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.

Technical note: Development of multiplex PCR assays for the molecular characterization of Streptococcus uberis strains isolated from bovine mastitis

“…These virulence genes were commonly detected among the Strep. uberis strains, as previously described (Reinoso et al, 2011;Parin et al, 2017;Boonyayatra et al, 2018). The higher distribution of these genes among the Strep.…”

“…It has also been identified as being responsible for a large part of clinical mastitis in several European countries such as Belgium, Germany, Italy, and the UK (Bradley et al, 2007;Krömker et al, 2014). The control of this environmental microorganism can be particularly problematic (Boonyayatra et al, 2018). Streptococcus uberis has several virulence genes; for example, the hyaluronic acid capsule genes (hasA, hasB, and hasC; Ward et al, 2001), the plasminogen activator A gene (pauA; Rosey et al, 1999), and the Strep.…”

“…Other virulence factors such as gapC (Pancholi and Fischetti, 1993), which encodes glyceraldehyde-3-phosphate dehydrogenase, or oppF (Smith et al, 2002), which is involved in the acquisition of essential amino acids from milk during bacterial growth, have previously been studied for their association with pathogenesis in IMI. A clear understanding of these virulence genes as key factors for mastitis development is still lacking (Boonyayatra et al, 2018). From previous studies (Perrig et al, 2015;Reinoso et al, 2015), it appears that in any given herd, only a limited group of Strep.…”

“…Multiplex PCR (mPCR) is an additional molecular tool for epidemiological studies and rapid characterization of Strep. uberis strains isolated from bovine mastitis milk (Boonyayatra et al, 2018).…”

“…uberis and the distribution of its virulence factors in isolates. The virulence factors included in these 2 mPCR assays are widely studied (Parin et al, 2017;Boonyayatra et al, 2018) and are thought to represent key factors in the invasion process of mammalian epithelial tissue for Strep. uberis.…”