Genomic and transcriptomic comparison between Staphylococcus aureus strains associated with high and low within herd prevalence of intra-mammary infection

Abstract

Background Staphylococcus aureus (Staph. aureus) is one of the major pathogens causing mastitis in dairy ruminants worldwide. The chronic nature of Staph. aureus infection enhances the contagiousness risk and diffusion in herds. In order to identify the factors involved in intra-mammary infection (IMI) and diffusion in dairy cows, we investigated the molecular characteristics of two groups of Staph. aureus strains belonging to ST8 and ST398, differing in clinical properties, through comparison of whole genome and whole transcriptome sequencing.ResultsThe two groups of strains, one originated from high IMI prevalence herds and the other from low IMI prevalence herds, present a peculiar set of genes and polymorphisms related to phenotypic features, such as bacterial invasion of mammary epithelial cells and host adaptation. Transcriptomic analysis supports the high propensity of ST8 strain to chronicity of infection and to a higher potential cytotoxicity.ConclusionsOur data are consistent with the invasiveness and host adaptation feature for the strains GTB/ST8 associated to high within-herd prevalence of mastitis. Variation in genes coding for surface exposed proteins and those associated to virulence and defence could constitute good targets for further research.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-017-0931-8) contains supplementary material, which is available to authorized users.

Comparative genomics of Staphylococcus aureus associated with subclinical and clinical bovine mastitis

“…also sequenced the genomes of six S . aureus strains (ST398 and ST8), that caused subclinical mastitis, which were divided into two groups (low and high within herd prevalence) [50]. Contrary to their findings, the gene that codes for the collagen binding protein ( cna ) was not found in the strains causing subclinical mastitis.…”

Distinct phenotypic traits of Staphylococcus aureus are associated with persistent, contagious bovine intramammary infections

“…Contradictory, a higher potential cytotoxicity for high within-herd prevalent ST8 strains was proposed by a recent study of Capra et al . 31 . Thus, further studies will be necessary, including different ST types, before firm conclusion can be drawn on the importance and role of strain cytotoxicity for S. aureus persistence in dairy cattle.…”

Milk microbial composition of Brazilian dairy cows entering the dry period and genomic comparison between Staphylococcus aureus strains susceptible to the bacteriophage vB_SauM-UFV_DC4

“…Although several genotypes of S. aureus have been identified and associated with high-herd prevalence 88,89 , most isolates can share up to 78% of conserved genes (core genome) independently from their isolation source 90 . Nowadays, it is reasonable to infer that host susceptibility, the presence of core-variable genes (e.g sdrD, clfA-B, sasD and fnbB) and their expression level are associated with the severity of mastitis 91,92 .…”

“…Apart from sequences specific for prophages (discussed above), genes coding for microbial surface components recognizing adhesive matrix molecules (MSCRAMM) proteins were found in the UFV2030RH1 genome and this is one of the main differences between the two isolates. Considered as members of the "core variable" genes, sdrD and sasG encode proteins that promote adhesion/colonization to host cells and contribute to biofilm formation 91,94 . Indeed, S. aureus UFV2030RH1 has demonstrated a stronger capability to adhere and form biofilms in bovine mammary epithelial cells (MAC-T) when compared to S. aureus 3059 (unpublished data).…”