Abstract
BackgroundStaphylococcus 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.
Highlights
Staphylococcus aureus (Staph. aureus) is one of the major pathogens causing mastitis in dairy ruminants worldwide
The strains isolated from three herds with high intra-mammary infection (IMI) prevalence were identified by Repetitive-sequence PCR (RS-PCR) as genotype B (GTB) and ST8 and none of them harboured the mecA gene coding for methicillin resistance
The sequencing reads from every sample were assembled obtaining an average of 95 number of large contigs (>500 nt) from all the samples (Additional file 4)
Summary
Staphylococcus aureus (Staph. aureus) is one of the major pathogens causing mastitis in dairy ruminants worldwide. 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. Staphylococcus aureus is one of the major cause of intra-mammary infection (IMI) in ruminants worldwide, causing mastitis with diverse degrees of severity. Aureus mastitis was investigated by using an integrated approach that includes NGS, microarray and proteomic data [22] providing the first high-resolution comparison between gene content and gene expression in two Staph. Gene expression analysis by microarray techniques has provided, information about global transcript changes [24, 25] or molecular basis of virulence [26] in Staph. RNA-seq was recently used to study (i) the gene expression in different Staph. aureus strains [27, 28], (ii) the role of anti-sense transcription [29] and (iii) the identification of small non-coding RNAs [30]
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