In vitro synergy of antibiotic combinations against planktonic and biofilm Pseudomonas aeruginosa

Abstract

Aim: The combination of different antimicrobial agents and subsequent synergetic effects may be beneficial in treatment of P. aeruginosa infec-Hossein Ghorbani 1,2 Mohammad Yousef tions. The aim of the present study was to determine antibiotic suscep-Memar 2,3 tibility patterns of clinical isolates of P. aeruginosa and the effect of Fatemeh Yeganeh Sefidan 2,3 different antibiotic combinations against the multidrug-resistant (MDR), biofilm-producing bacterium P. aeruginosa. Methods: Thirty-six P. aeruginosa clinical isolates were evaluated. The disk diffusion method was performed to determine antibiotic suscepti-Mina Yekani 2,3 Reza Ghotaslou 2 bility patterns according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. The minimum inhibitory concentration of antimicrobial agents for the test organisms was determined by the broth mi-1 Infectious and Tropical crodilution method. To determine synergetic effects of the combinations Diseases Research Center, of agents, the checkerboard assay and the fractional inhibitory concen-Tabriz University of Medical tration were used. The biofilm inhibitory concentration was determined Sciences, Tabriz, Iran to detect any inhibitory effect of antibiotics against the biofilm. 2 Department of Microbiology, Results: High levels of resistance were detected against most antibiotics, School of Medicine, Tabriz except colistin and polymyxin. According to the disk diffusion method, University of Medical 58.3% of isolates were MDR. A synergetic effect between amika-Sciences, Tabriz, Iran cin/ceftazidime, tobramycin/colistin and ceftazidime/colistin was found 3 Students' Research in 55.6%, 58.3% and 52.8% of isolates, respectively. A significant syn-Committee, Tabriz University ergetic effect against biofilm-producing isolates was observed for the of Medical Sciences, Tabriz, combination of tobramycin (0.5-1 mu g/ml) and clarithromycin (256-512 Iran mu g/ml). Conclusion: Combinations of antibiotics have a different activity on the biofilm and planktonic forms of P. aeruginosa. Consequently, separate detection of antibacterial and antibiofilm effects of the antibiotic combinations may be useful in guiding the antibiotic therapy.