Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Wed, 12 Dec 2018 14:32:00 Carriage of both the fnbA and fnbB genes and growth at 37 6C promote FnBP-mediated biofilm development in meticillin-resistant Staphylococcus aureus clinical isolates Eoghan O’Neill, 1,2 Hilary Humphreys 2 and James P. O’Gara 1 Correspondence James P. O’Gara jim.ogara@ucd.ie 1 UCD School of Biomolecular and Biomedical Science, Ardmore House, University College Dublin, Belfield, Dublin 4, Ireland 2 Department of Clinical Microbiology, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland Received 30 July 2008 Accepted 6 December 2008 The Staphylococcus aureus FnBPA and FnBPB proteins promote acid-induced biofilm accumulation. Meticillin-resistant S. aureus (MRSA) isolates from device-related infections with both fnbA and fnbB produced significantly more biofilm than isolates with either gene alone. Under mildly acidic growth conditions, FnBP-mediated biofilm and fnbA and fnbB transcript levels were substantially higher during growth at 37 6C than at 30 6C. Thus, in addition to a lowered pH, carriage of both fnbA and fnbB and growth at 37 6C promote MRSA biofilm development, further supporting a role for the FnBPA and FnBPB surface proteins in the pathogenesis of MRSA device-related infections. INTRODUCTION Since the early 1950s, polymers have been used in the construction of medical devices such as central and peripheral intravascular lines, surgical drains and prosthetic joints (Montdargent & Letourneur, 2000). Bacteria such as staphylococci that originate from the patient’s microflora or exogenously from healthcare personnel or the hospital environment can gain access to the medical device by migration externally from the skin or, as in the case of lines and drains, internally from the catheter hub or port. Occasionally, devices may become haematogenously seeded from another focus of infection. More uncommonly, infusate contamination leads to catheter-related bloodstream infection (O’Grady, 2002). Guidelines on the prevention of device-related infection therefore focus on (i) education and training of healthcare providers who insert and maintain intravascular lines and drains, (ii) maximal sterile barrier precautions during device insertion and (iii) appropriate skin antisepsis prior to device insertion (O’Grady, 2002). Following insertion into the patient, medical devices are rapidly coated with a conditioning film composed primarily of host-derived extracellular matrix proteins. Some of these host proteins can act as receptors for bacterial attachment and can thus play an important role in the early stages of biofilm development (O’Gara, 2007). Staphylococcus aureus can bind to a wide range of host matrix proteins, adherence to which is mediated by a group of S. aureus surface proteins termed MSCRAMMs ( microbial surface components recognizing adhesive matrix molecules) (Foster & Hook, 1998). Following this initial attachment to an implanted device, biofilm forma- tion involves a cellular accumulation process. In staphylo- cocci, the exopolysaccharide termed polysaccharide intercellular adhesin or polymeric N-acetylglucosamine (PIA/PNAG) and the surface proteins accumulation- associated protein (Aap), biofilm-associated protein (Bap) and S. aureus surface protein G (SasG) have all been implicated in biofilm accumulation (reviewed by O’Gara, 2007). We recently described a new S. aureus biofilm accumulation phenotype mediated by the multi- functional fibrinogen- and fibronectin-binding proteins FnBPA and FnBPB. FnBP-mediated biofilm development appears to be more commonly associated with meticillin- resistant S. aureus (MRSA) isolates than with meticillin- sensitive S. aureus (MSSA) isolates (O’Neill et al., 2008). Furthermore, FnBP-promoted biofilm development by MRSA isolates is triggered by mild acid stress, whereas PIA/PNAG-mediated biofilm development by MSSA iso- lates is generally induced by osmotic stress (Fitzpatrick et al., 2005; O’Neill et al., 2007, 2008). FnBP-mediated biofilm development is dependent on the Staphylococcus accessory regulator SarA but not at the level of fnbA and fnbB transcription (O’Neill et al., 2008). Here, we examined the relationship between carriage of the fnbA and/or fnbB genes and biofilm-forming capacity in a Abbreviations: CC, clonal complex; MLST, multilocus sequence typing; MRSA, meticillin-resistant Staphylococcus aureus; MSSA, meticillin- sensitive S. aureus. Journal of Medical Microbiology (2009), 58, 399–402 DOI 10.1099/jmm.0.005504-0 005504 G 2009 SGM Printed in Great Britain 399