Biocide susceptibility of the Burkholderia cepacia complex.
OBJECTIVE
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.
Rose
Helen
H
Cardiff School of Biosciences, Cardiff University, Cardiff, UK.
Baldwin
Adam
A
Dowson
Christopher G
CG
Mahenthiralingam
Eshwar
E
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D018441:Biofilms / Q000254:growth & development; D042602:Burkholderia cepacia complex / Q000187:drug effects* / Q000502:physiology; D004202:Disinfectants / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests
D000900:Anti-Bacterial Agents; D004202:Disinfectants