Journal
MICROBIAL PATHOGENESIS
Volume 48, Issue 1, Pages 18-27Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.micpath.2009.10.003
Keywords
Mastitis; Cystic fibrosis; Chronic infections; SarA; SigB; agr
Categories
Funding
- Canadian Cystic Fibrosis Foundation l
- Natural Science and Engineering Research Council of Canada
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Staphylococcus aureus small-colony variants (SCVs) and biofilms are linked to chronic infections. it is known that the presence of aminoglycoside antibiotics may contribute to the emergence of SCVs and it is thought that molecular mechanisms are involved in the ability of S. aureus to adopt this phenotype. No study has addressed the possible role of the stress- and colonization-related alternative sigma factor B (SigB) in the emergence of SCVs, although a sustained SigB activity was reported in these variants. Here, we demonstrate that SigB is involved in the emergence of SCVs resulting from an exposure to a sub-inhibitory concentration of aminoglycosides. Monitoring of gene expression in an aminoglycoside-treated prototypical strain or in clinical SCVs showed the activation of SigB, whereas the accessory gene regulator (agr) system was not. Furthermore, gentamicin-treated prototypical bacteria and SCVs had an increased ability to form biofilm only in a SigB functional background. The administration of a subinhibitory concentration of gentamicin significantly increased the formation of SCVs for a prototypical strain but not for the sigB mutant in a mouse model of S. aureus-induced mastitis. Collectively, our results show that SigB may positively influence the appearance of S. aureus SCVs and the production of biofilm upon aminoglycoside exposure. (C) 2009 Elsevier Ltd. All rights reserved.
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