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Eur J Clin Microbiol Infect Dis 2009 Oct;28(10):1275-9. Epub 2009 Jul 3.

Combination antibiotic susceptibility of biofilm-grown Burkholderia cepacia and Pseudomonas aeruginosa isolated from patients with pulmonary exacerbations of cystic fibrosis.

Dales L, Ferris W, Vandemheen K, Aaron SD

The Ottawa Health Research Institute, University of Ottawa, Ottawa, ON, Canada. 5ld14@queensu.ca

Abstract

We identified double and triple antibiotic combinations effective against biofilm-grown Burkholderia cepacia and Pseudomonas aeruginosa sampled from cystic fibrosis (CF) patients undergoing acute pulmonary exacerbations. Sputum bacteria from 110 CF patients were grown as biofilms. Combination antibiotic susceptibility testing was used to test 94 double and triple antibiotic combinations. Biofilm-grown bacterial isolates were less susceptible to antibiotic combinations compared to the same bacterial isolates grown planktonically (P < 0.001). Fifty-nine percent of biofilm-grown B. cepacia isolates and 29% of P. aeruginosa isolates were resistant to all double antibiotic combinations tested. Triple antibiotic combinations were more effective than double antibiotic combinations against biofilms (P < 0.0001). For P. aeruginosa biofilms, the addition of azithromycin or rifampin to otherwise effective antibiotic combinations was frequently associated with antagonism. Bacterial biofilms of CF organisms are highly resistant to antibiotics. This study identified potentially effective antibiotic combinations to guide the empirical treatment of CF pulmonary exacerbations.

 

Tables

 

Table 1:  Inhibitory activity of the most effective double and triple antibiotic combinations against pseudomonas aeruginosa biofilm-grown isolates.

 

Table 2:  Inhibitory activity of the most effective double and triple antibiotic combinations against Burkholderia cepacia biofilm-grown isolates