Staphylococcus aureus Sbi and SpA proteins have important effects in the development of sub-cutaneous abscess in mice

GONZALEZ CINTIA; LEDO CAMILA; GOMEZ MARISA

Lucca

Conferencia; Staphylococcal Diseases; 2015

Gordon Reseach Conference

Staphylococcus aureus is an important human pathogen that causesinfections with high morbidity and mortality. The protein A(SpA) and the Staphylococcal binding immunoglobulin protein (Sbi) arestrong evasion factors. In addition, we have demonstrated theirability to induce the production of pro-inflammatory cytokines andchemokines in vitro and in vivo. This study was aimed at elucidatingthe contribution of SpA and Sbi to the development of abscess in amodel of skin infection, in which an appropriate inflammatory responseis known to be required to contain the bacteria. Mice were inoculatedby subcutaneous route with 1x108 CFU of S.aureus strain Newman or theisogenic mutants that do not express Sbi (Sbi-), SpA (SpA-) or both(SpA-Sbi-). S.aureus caused abscesses with a median area of 0.70 cm2(min 0.35; max 1.09), and a bacterial burden of 3.5x107 CFU (min8x106; max 2.4x108) at day three after inoculation. Bacterial dissemination to the lung, spleen, liver and kidney was observed inmore than 64% percent of the animals. The bacterial burden in theabscesses induced by the Sbi- mutant was significantly higher thanthat observed in S.aureus inoculated mice (p 0,05). The areas of theabscesses induced by SpA- and the SpA-Sbi- mutant were significantlybigger than those evoked by S.aureus and the Sbi- mutant (p 0.01). Thebacterial burden was significantly higher than that observed afterS.aureus challenge (p 0,05) and similar to that observed in miceinoculated with the Sbi- mutant. No differences were found in distalorgan colonization among the strains evaluated. These results suggestthat in the skin infection model evaluated, SpA and Sbi may play animportant role not only in limiting the size of the lesion but alsocontributing to early bacterial eradication in the local foci.Future work evaluating the evolution and potential resolution of theabscesses will allow a better understanding of the role of theseproteins in staphylococcal skin infection