Distribution of virulence-associated genes in Streptococcus uberis isolated from bovine mastitis

Abstract

Streptococcus uberis is an important pathogen that has been implicated in bovine mastitis but the virulence factors associated with pathogenesis are not well understood. The aim of this work was to examine 11 putative and known virulence-associated genes by PCR in 78 S. uberis strains isolated from infected animals in Argentina. Additionally, the distribution of virulence patterns over various herds was determined. Not all genes were present in the strains but all of the detected virulence-associated genes were present in combination. Forty-seven (60.3%) isolates carried seven to 10 virulence-associated genes. Further analysis revealed 58 virulence patterns. Different patterns were found within the same herd and among herds, demonstrating that strains with different virulence patterns were able to cause mastitis. Despite the large number of strains with different virulence patterns, strains with identical patterns was found. Detection of virulence-associated genes in individual S. uberis strains isolated from infected animals revealed one to 10 virulence genes. This may indicate that other virulence factors could be involved. The present study reveals the occurrence and distribution of 11 virulence-associated genes among S. uberis isolates from bovine mastitis in various herds and contributes to a better understanding of the pathogenicity of this bacterium.

Genetic diversity and virulence genes in Streptococcus uberis strains isolated from bovine mastitis

“…PFGE demonstrated a high discriminatory index (0.9889) in accordance with previous studies (DOUGLAS et al, 2000;LASAGNO et al, 2011;PHUEKTES et al, 2001;RATO et al, 2008RATO et al, , 2013. Four pulse-types found by PFGE (VI, VII-a, VIII, and IX) showed two strains with similar patterns that were classified as having identical restriction patterns (Figure 1).…”

“…According to these authors, the low frequency of this gene could be explained by the presence of other activators of plasminogen. A few studies assessed the gene skC in S. uberis, but all of these reports found its frequency to be similar to that of pauA (JOHNSEN et al, 1999, KHAN et al, 2003, REINOSO et al, 2011, SHOME et al, 2012.…”

“…uberis is a very important environmental pathogen that causes bovine mastitis (ALMEIDA et al, 2006;LASAGNO et al, 2011;PERRIG et al, 2015). According to Hillerton and Berry (2003), environmental Streptococci are responsible for about one-third of all clinical mastitis cases worldwide, and IMI caused by these bacteria is closely associated with poor environmental or milking hygiene conditions.…”

“…Previous studies showed similar results for isolates from clinical mastitis, suggesting that these strains are the predominant ones in the environment. Although S. uberis is predominantly an environmental pathogen, its transmission could be from animal to animal as a contagious mastitis pathogen (ABUREEMA et al, 2014;DOUGLAS et al, 2000;LASAGNO et al, 2011).…”

“…These approaches may permit the development of more effective control measures for this microorganism. Among the different molecular typing methods, the Pulsed Field Gel Electrophoresis (PFGE) technique has been used to study pathogens involved in the etiology of bovine mastitis because it is highly discriminatory and highly reproducible (BASEGGIO et al, 1997;DOUGLAS et al, 2000;LASAGNO et al, 2011;PHUEKTES et al, 2001;RATO et al, 2008RATO et al, , 2013. According to Shome et al (2012), PFGE is the technique of choice for short-term or local epidemiological analyses.…”