Abstract
Staphylococcus aureus is a highly prevalent cause of mastitis in dairy herds worldwide, capable of causing outcomes that vary from subclinical to peracute gangrenous mastitis. We performed a comparative genomic analysis between 14 isolates of S. aureus, originating from peracute bovine mastitis with very severe signs (9 gangrenous, 5 non-gangrenous) and six isolates originating from subclinical or clinical mastitis with mild to moderate signs, to find differences that could be associated with the clinical outcome of mastitis. Of the 296 virulence factors studied, 219 were detected in all isolates. No difference in the presence of virulence genes was detected between the peracute and control groups. None of the virulence factors were significantly associated with only a single study group. Most of the variation in virulence gene profiles existed between the clonal complexes. Our isolates belonged to five clonal complexes (CC97, CC133, CC151, CC479, and CC522), of which CC522 has previously been detected only in isolates originating from caprine and ovine mastitis, but not from bovine mastitis. For statistical analysis, we sorted the CCs into two groups. The group of CCs including CC133, CC479, and CC522 was associated with gangrenous mastitis, in contrast to the group of CCs including CC97 and CC151. The presence of virulence genes does not explain the clinical outcome of mastitis, but may be affected by allelic variation, and especially different regulation and thus expression in the virulence genes.
Highlights
Staphylococcus aureus (S. aureus) is a significant cause of mastitis in ruminants such as cows, sheep, and goats worldwide (Bergonier et al, 2003; Keane, 2019; Vasileiou et al, 2019)
No previous studies have performed a comparative genomic analysis focusing on S. aureus isolates from peracute bovine mastitis
This is most likely because peracute S. aureus mastitis cases occur rarely and collecting the isolates is time-consuming
Summary
Staphylococcus aureus (S. aureus) is a significant cause of mastitis in ruminants such as cows, sheep, and goats worldwide (Bergonier et al, 2003; Keane, 2019; Vasileiou et al, 2019). Staphylococcus aureus mastitis has been detected in other animal species, such as rabbits (Corpa et al, 2009) and dogs (Hasegawa et al, 1993), as well as in humans (Angelopoulou et al, 2018). Severe peracute gangrenous mastitis has been detected in other ruminants such as sheep (Vautor et al, 2009) and goats (Rainard et al, 2018b), in other animals such as rabbits (Corpa et al, 2009), and in human females (Agrawal et al, 2014)
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