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Characterization of serine-aspartate rich (Sdr) proteins in Staphylococcus aureus isolates from bovine intramammary infections in Canada.

A. Dubé-Duquette



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Characterization of serine-aspartate rich (Sdr) proteins in Staphylococcus aureus isolates from bovine intramammary infections in Canada.
A. Dubé-Duquette*1, É. Demontier1, J.-F. Lucier1, S. Rodrigue1, J.-P. Roy2, C. Ster3, F. Malouin1. 1Département de Biologie, Faculté des Sciences, Université de Sherbrooke Sherbrooke, QC, Canada, 2Département de Sciences Cliniques, Faculté de Médecine Vétérinaire, Université de Montréal St-Hyacinthe, QC, Canada, 3Agriculture and Agri-Food Canada, Sherbrooke Research and Development Centre Sherbrooke, Qc, Canada.

Many Staphylococcus aureus surface proteins represent key elements in the pathogenic process leading to bovine intramammary infection (IMI) and mastitis. We characterized the diversity of serine-aspartate repeat (Sdr) surface proteins found in S. aureus strains collected from quarter milk samples in Canada. Strains were selected to represent the main spa-types found in Canadian dairy cattle (t529, t267, t359, t605, t13401, t2445). Two groups (t605 and t13401) were strong biofilm producers and spa type t2445 was composed of weak biofilm producer strains. The spa type t529 was the most prevalent and associated with the presence of the superantigen gene seg. Whole-genome sequencing data from the mastitis-associated S. aureus strains (36 strains in total) was used to analyze the distribution of 3 specific sdr genes (sdrC, sdrD and sdrE) in the different spa groups. SdrC was present in all studied strains except one from the t13401 group. Interestingly, strains from t605 and t529 had the same mutation leading to an early stop codon in sdrC. Also, there was a deletion of 330 bases in the sdrC gene of t2445 strains (the low-biofilm producers), occurring in a repeated region of the protein rather than in the functional region. SdrE was found in all spa groups except for t13401. Surprisingly, an allelic variant of sdrE was noticed in t529 isolates. This variant, named bone sialoprotein-binding protein, is characterized by a modified functional domain of the protein and was previously linked to strains leading to bone infections in humans. SdrD was present in 3 spa types (t267, t2445 and t359) and its sequence was very similar in all those strains. These results revealed that most S. aureus strains from quarter milk samples carry sdrC and sdrE and that important sequence differences exist between some spa groups. However, sdrD seems less common. Considering that S. aureus can cause variable infection patterns in dairy cattle, understanding the diversity of virulence factors should lead to a better identification of problematic strains and lead to more precise herd management decisions.

Keywords: bovine mastitis, Staphylococcus aureus.

Biography: I recently completed the first year of my master's degree in professor Malouin's organization. I have also done three undergraduate internships in the past to gain experience in the field of dairy science and animal health. Until now, I mostly focused my research work on the caracterization and the treatment of dairy cattle pathogens.