Differential ability of Staphylococcus aureus from diverse agr groups to invade mammary epithelial cells.

BUZZOLA FR; ALVAREZ LP; TUCHSCHERR LPN; BARBAGELATA MS; LATTAR SM; CALVINHO LF; SORDELLI DO

INFECTION AND IMMUNITY

ASM Press

Lugar: Washington DC, USA; Año: 2007 vol. 75 p. 886 - 891

0019-9567

Staphylococcus aureus is the most frequently isolated bacteria from milk of bovines with mastitis. Four allelic groups  -which interfere with the regulatory activity among the different groups-  have been identified in the accessory gene regulator (agr) system. The aim of this study was to ascertain the prevalence of the different agr groups in capsulated and non-capsulated S. aureus isolated from mastitic bovines in Argentina and whether a given agr group was associated with MAC-T cell invasion and in vivo persistence. Eighty-eight percent of bovine S. aureus strains were classified as agr group I. The remainder belonged in agr groups II, III and IV (2, 8 and 2%, respectively). By restriction fragment length polymorphism analysis after PCR amplification of the agr locus variable region, 6 agr restriction types were identified. All agr group I strains presented an unique allele (A/1), whereas strains from groups II, III and IV exhibited higher diversity. Bovine S. aureus strains defined as agr group I (capsulated or non-capsulated) showed a significantly increased ability to be internalized within MAC-T cells, compared with isolates from agr groups II, III and IV. Agr-groups II or IV S. aureus strains were cleared more efficiently than agr-group I strains from the murine mammary gland. The results suggest that agr-group I S. aureus strains are more efficiently internalized within epithelial cells and can persist in higher numbers in mammary gland tissue than S. aureus strains classified as agr groups II, III or IV.