CONCISE ARTICLE Comparison of antibiotic susceptibility of Burkholderia cepacia complex organisms when grown planktonically or as biofilm in vitro E. Caraher & G. Reynolds & P. Murphy & S. McClean & M. Callaghan Published online: 30 January 2007 # Springer-Verlag 2007 Abstract This study determined the antibiotic suscepti- bility of planktonic and biofilm cultures of Burkholderia cepacia complex organisms, a group of highly problematic pathogens associated with cystic fibrosis patients. The biofilm inhibitory concentrations were considerably higher than the corresponding minimum inhibitory concentrations for meropenem and piperacillin-tazobactam. However, tobramycin and amikacin were efficacious against both biofilm and planktonic cultures. Overall this study showed that biofilm susceptibility testing might be more clinically appropriate for determining antibiotic therapy for Burkholderia cepacia complex infections in cystic fibrosis patients. Introduction Burkholderia cepacia complex (Bcc) is a group of gram- negative bacteria comprised of at least nine species that have emerged as opportunistic pathogens in CF patients [1]. Although all nine Bcc species have been isolated from CF sputa, colonisation by B. multivorans and B. cenocepacia (formerly Genomovar II and III) is more common among CF patients [2]. Pulmonary colonisation with certain Bcc organisms has been associated with an accelerated clinical decline and an increased risk of death [1]. Recently, evidence has emerged that Bcc strains grow as biomasses in the mucus of the lung [3] and form biofilms in vitro [4]. Important consequences of biofilm formation with pro- found clinical implications include markedly enhanced resistance to antibiotics and disinfectants and protection from host defence [5]. Aggressive antibiotic therapy is employed to suppress Bcc growth and the damage it causes in the lungs of CF patients. However, the MICs of antibiotics can dramatically increase when bacteria grow in biofilms [5]. Clinical microbiological testing routinely involves assessing the antibiotic susceptibility of planktonically cultured bacteria obtained from the sputum of CF patients and may not be relevant to the actual susceptibilities of bacteria that exist in the lung as biofilms. Recently published studies have compared the antibiotic susceptibility of Pseudomonas aeruginosa in differing modes of growth [6]; however, to date, few publications exist that address the susceptibility of Bcc grown as biofilms to anti-pseudomonal agents [7, 8]. Furthermore, the studies that have been performed were limited to investigating the susceptibilities of single Bcc strains. The objective of the study reported here was to compare the antibiotic resistance profiles of strains of Bcc from three species and to establish which of eight antibiotics is the most efficacious for eliminating the biofilms. In addition, the susceptibilities of the strains to anti-pseudomonal Eur J Clin Microbiol Infect Dis (2006) 26:213–216 DOI 10.1007/s10096-007-0256-x E. Caraher : G. Reynolds : S. McClean : M. Callaghan (*) Department of Applied Science and National Institute of Cellular Biotechnology (NICB), Institute of Technology Tallaght (ITT-Dublin), Tallaght, Dublin 24, Ireland e-mail: maire.callaghan@ittdublin.ie P. Murphy The Adelaide, Meath Incorporating the National Children’ s Hospital (AMNCH), Tallaght, Dublin 24, Ireland P. Murphy Department of Clinical Microbiology, Trinity College, Dublin 2, Ireland