Bactericidal activity of various antibiotics versus tetracycline-loaded chitosan microspheres against Pseudomonas aeruginosa biofilms

Abstract

The discovery of biofilms in 1980’s has brought much interest to the study of the contribution of bacterial biofilms with many recurrent and chronic infectious diseases. In this study, we evaluated the utility of chitosan microspheres in delivering antibiotic in dosage form that could be effective against Pseudomonas aeruginosa (P. aeruginosa) biofilms. P. aeruginosa isolates were collected and identii¬ed using standard methods. A modii¬ed microtitre plate test was used to determine the bioi¬lm-forming capacity of the isolates. Moreover, bactericidal activity of various antibiotics vs. tetracycline-loaded chitosan microspheres against P. aeruginosa sessile and planktonic cells was tested. Results showed that, most P. aeruginosa strains (92.9%) were efficient biofilm producer-strains. There were differences in the antibiotic susceptibility of planktonic and sessile cell populations. Fluoroquinolones, aminoglycoside and tetracycline showed more potent activity (MIC50 was 0.8, 4.88 and 34.19 μg/ml, respectively) than penicillin, cephalosporin, clarithromycin and macrolides. Bioi¬lm growth was inhibited after 3 h treatment with 2x and 4x MICs and after 24 h treatment with MIC of tetracycline-loaded chitosan microspheres prepared by coacervation method than that prepared by water in oil emulsion method. This was correlated to the cumulative amount of tetracycline that was released from tetracycline-loaded chitosan microspheres prepared by coacervation method which released about 60% of tetracycline in the first 6 h and continued for 24 h. This in the clinical field may be translated into maintaining constant drug concentration for a prolonged period and maximize the therapeutic effect of antibiotics while minimizing antibiotic resistance and improved patient compliance. So, the use of tetracycline-chitosan microspheres may be a new strategy for the development of a specific drug delivery system to increase the efficacy of tetracycline against biofilm-associated P. aeruginosa infections. However, it would be appropriate to conduct clinical studies to confirm this. Key words: Bioi¬lm formation of Pseudomonas aeruginosa, tetracycline, antimicrobial susceptibility, microtiter plate method, drug-loaded chitosan microsphere.