Internalization of Staphylococcus aureus into epithelial cells: influence of alleles of the agr locus.

ALVAREZ, LP; TUCHSCHERR, LPN; LATTAR, SM; BARBAGELATA, MS; CACCURI RL; BUZZOLA, FR; SORDELLI, DO

Atlanta, Georgia, EEUU de NA

Congreso; 105th Annual Meeting of the American Society for Microbiology (ASM); 2005

American Society for Microbiology

Staphylococcus aureus strains can be classified into four agr (accessory gene regulator) specificity groups based on agr locus variable region polymorphisms. Adherence to and intracellular survival of S. aureus within mammary gland epithelial cells are probably important steps in the pathogenesis of bovine persistent intramammary infection.  S. aureus persistence in the mammary gland may be favored in isolates belonging in a certain agr group due to bacterial interference.  In the present work, we investigated the relationship between agr group and mammary  gland epithelial (MAC-T) cell line invasion.  To this purpose, S. aureus isolated from bovines with subclinical or clinical mastitis were classified by an agr group-specific multiplex PCR.  Seventy-five, 15 and 10 percent of the isolates belonged in agr groups I, II and IV, respectively.  Intracellular survival of S. aureus into MAC-T cells was investigated by a gentamicin protection assay.  Two hours post-infection, subclinical isolates classified as agr-group II (231±86 UFC/ml) showed a significantly low ability to internalize MAC-T cells when compared with those of group I (2061±590 UFC/ml, p=0.035) or group IV (1465±482 UFC/ml, p=0.027, Mann-Whitney test).  Similar results were observed between isolates from bovine with clinical mastitis (agr groups I vs II: 3980±1791 vs 22±10 UFC/ml, p=0.003).  S. aureus-induced apoptosis was undetectable in MAC-T cells infected with strains classified as agr-group IV.  However, the ability of S. aureus isolates agr-groups I or II to induce apoptosis in MAC-T cells was observed.  These data suggest that S. aureus agr-group IV may have an advantage to reside within epithelial cells  thus leading to persistent disease.