Existence of two groups of Staphylococcus aureus strains isolated from bovine mastitis based on biofilm formation, intracellular survival, capsular profile and agr-typing

Abstract

A B S T R A C TStaphylococcus (S.) aureus is recognised worldwide as an important pathogen causing contagious acute and chronic bovine mastitis. Chronic mastitis account for a significant part of all bovine cases and represent an important economic problem for dairy producers. Several properties (biofilm formation, intracellular survival, capsular expression and group agr) are thought to be associated with this chronic status. In a previous study, we found the existence of two groups of strains based on the association of these features. The aim of the present work was to confirm on a large international and non-related collection of strains the existence of these clusters and to associate them with case history records. In addition, the genomes of eight strains were sequenced to study the genomic differences between strains of each cluster. The results confirmed the existence of both groups based on capsular typing, intracellular survival and agr-typing: strains cap8-positive, belonging to agr group II, showing a low invasion rate and strains cap5-positive, belonging to agr group I, showing a high invasion rate. None of the two clusters were associated with the chronic status of the cow. When comparing the genomes of strains belonging to both clusters, the genes specific to the group "cap5-agrI" would suggest that these strains are better adapted to live in hostile environment. The existence of these two groups is highly important as they may represent two clusters that are adapted differently to the host and/or the surrounding environment.

Frequency of Staphylococcus aureus virulence genes in milk of cows and goats with mastitis

“…The existence of two groups of S. aureus strains isolated from bovine mastitis based on capsular typing, intracellular survival and agr-typing was confirmed by Bardiau et al (2016). They hypothesized that the first group "cap5-agrI" may correspond to strains adapted to the intracellular niche leading to chronic infection and that the second group "cap8-agrII" may correspond to strains better adapted to the extracellular niche leading to acute infection.…”

“…They hypothesized that the first group "cap5-agrI" may correspond to strains adapted to the intracellular niche leading to chronic infection and that the second group "cap8-agrII" may correspond to strains better adapted to the extracellular niche leading to acute infection. The existence of these two groups is highly important as they may represent two clusters that are adapted differently to the host and/or the surrounding environment (Bardiau et al 2016).…”

“…Several characteristics contribute for the pathogenesis and spread of S. aureus including virulence factors, the host and the environment (Roberson et al 1998, Barkema et al 2006. Previous studies suggest that existing phenotypic and genotype diversity between groups of S. aureus would make that some of these strains are better adapted to live in hostile environment (Bardiau et al 2014(Bardiau et al , 2016. This bacterium can cause a broad range of diseases due to an abundance of virulence factors that facilitate attachment, colonization, tissue invasion, toxinosis, and immune evasion, including adhesion proteins, enterotoxins and capsular polysaccharides (Zecconi et al 2006, Piccinini et al 2010.…”

Genomic investigation of Staphylococcus aureus isolates from bulk tank milk and dairy cows with clinical mastitis

“…In general, various types of virulence genes have been detected in clinical and subclinical mastitis isolates and in bulk tank milk (BTM). These virulence factors are involved in: Host colonization (cap, clfA/B, cna, fib and sak), toxin production (tst, sea-j, hla/b/g, lukD/E/FS, etA/B) and biofilm formation (icaD, fnbB) (Fueyo et al, 2005) (Bardiau et al, 2016)(Xu et al, 2015)(Fournier et al, 2008. Many of these virulence genes encode toxins that are also harmful to humans.…”

Draft Genome Sequence of a Sequence Type 398 Methicillin-Resistant Staphylococcus aureus Isolate from a Danish Dairy Cow with Mastitis

“…NC_021323). Virulence genes ( aur , cap , fib, hla, hlb, hlg, icaD , and nuc ) that previously have been found in S. aureus strains from cattle with mastitis and in bulk-tank milk were detected (11, 12). Last, a single hsdM gene from a type 1 restriction-modification (RM) system was identified via Restriction-Modification Finder 1.1 (http://cge.cbs.dtu.dk).…”