Detection of Staphylococcus aureus adhesion and biofilm-producing genes and their expression during internalization in bovine mammary epithelial cells

Abstract

Staphylococcus aureus is one of the most prevalent pathogens isolated from bovine mastitis,causing chronic intramammary infections (IMI) that limit profitable dairying. The course ofinfection is often associated with factors both related to the host and the bacterium. Aims of thisstudy were to select S. aureus isolates from bovine IMI with different genotypic profiles harboringgenes involved in adherence and biofilm production, to determine the behavior of these strains incontact with bovine mammary epithelial cells (MAC-T) and the expression of those genes duringbacterial-cell early interactions. The genetic diversity of 20 S. aureus strains that were isolated frommilk samples taken from cows with persistent-P and non-persistent-NP IMI was high, discriminatedinto 13 fingerprint groups. The occurrence of genes coding for S. aureus surface proteins (clfA, clfB,fnbA, fnbB, fib, cna) and biofilm formation (icaA, icaD, icaC, bap) and in vitro biofilm-formingability was not related to strain clinical origin (NP or P). Internalization of S. aureus into MAC-Tcells was strain-dependent and internalized bacteria overexpressed adherence and biofilm-forminggenes compared with those that remained in the supernatant of co-cultures; particularly those genesencoding FnBPs and IcaD. Strains yielding highest invasion percentages were those able tooverexpress fnBP, irrespectively of the presence of other evaluated genes. Strains from NP IMIshowed a greater multiplication capacity in vitro compared with strains from P IMI. These resultsprovide new insights about S. aureus differential gene expression of adhesion-internalization factorsduring early interaction with mammary epithelial cells.