JAC Advance Access originally published online on January 18, 2009
Journal of Antimicrobial Chemotherapy 2009 63(3):502-510; doi:10.1093/jac/dkn540
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Original research |
Biocide susceptibility of the Burkholderia cepacia complex
1 Cardiff School of Biosciences, Cardiff University, Cardiff CF10 3TL, UK 2 Department of Biological Sciences, Warwick University, Coventry CV4 7AL, UK
Received 22 September 2008; returned 30 October 2008; revised 9 December 2008; accepted 15 December 2008
* Corresponding author. Tel: +44-29-20875875; Fax: +44-29-20874305; E-mail: mahenthiralingame{at}cardiff.ac.uk
Objectives: The Burkholderia cepacia complex (Bcc) species are important opportunistic pathogens with intrinsic antibiotic resistance. They are also well known as contaminants of disinfectants, yet their biocide susceptibility has not been studied in detail. We investigated Bcc biocide susceptibility and correlated it to their taxonomy, antibiotic susceptibility and ability to form biofilms.
Methods: Genetically distinct Bcc strains belonging to 12 of the defined species were examined. Biocide susceptibility was assessed by (i) broth dilution MIC assays, (ii) agar growth-based MBC screens and (iii) suspension tests. Antibiotic MIC was determined by Etest® strips, and the ability to form biofilms was examined in a 96-well plate assay.
Results: Biocide susceptibility varied across the Bcc complex with high MIC recorded for chlorhexidine (>100 mg/L), cetylpyridinium chloride (>200 mg/L), triclosan (>500 mg/L), benzalkonium chloride (>400 mg/L) and povidone (>50 000 mg/L). Species-dependent differences were apparent only for cetylpyridinium chloride. There was no correlation between biocide susceptibility and (i) antibiotic susceptibility or (ii) the ability to form biofilms. Biocide MBC was considerably higher than the MIC (chlorhexidine, 6-fold greater; cetylpyridinium chloride, 20-fold greater). Cystic fibrosis outbreak strains (Burkholderia multivorans Glasgow strain and Burkholderia cenocepacia ET12) possessed elevated chlorhexidine resistance, and Bcc bacteria were also shown to remain viable in current commercial biocide formulations.
Conclusions: Bcc bacteria are resistant to a wide range of biocides and further representatives of this group should be included as reference strains in the development of new anti-infectives and commercial formulations.
Keywords: antibiotics , resistance and susceptibility , minimal inhibitory concentration