Open Access Research Article Pharmaceutica Analytica Acta Mahmoud et al., Pharmaceut Anal Acta 2012, S15 http://dx.doi.org/10.4172/2153-2435.S15-007 Special Issue 15 • 2012 Pharmaceut Anal Acta ISSN: 2153-2435 PAA, an open access journal Keywords: Biofilm formation of P. aeruginosa; Tetracycline; Antimicrobial susceptibility; Microtiter plate method; Drug-loaded chitosan microsphere Introduction P. aeruginosa is one of the most important opportunistic human pathogens. It has emerged as a dominant pulmonary pathogen with biofilm-forming capability, resulting in progressive chronic pulmonary infections, cystic fibrosis [1]. here is also an increasing awareness of the important role of P. aeruginosa biofilms in the contamination of medical biomaterials such as catheters and prostheses. Biofilm infections are diicult to eradicate with antimicrobial treatment, and in vitro susceptibility tests show considerable resistance of biofilm cells to killing [2]. Biofilms are deined as microbial-derived sessile communities attached to a surface and embedded in a self-produced polymeric matrix. hey play a central role in the pathogenesis of serious infections caused by P. aeruginosa. Bacteria grown in biofilms are more resistant to antimicrobial agents than their planktonic counterparts [3]. Susceptibility testing of planktonic bacteria may fail to predict in vivo resistance of device-related infections to antimicrobial agents. Standardized laboratory models to test antimicrobial agents in biofilms are still lacking, although a broad range of models for quantifying treated vs. untreated biofilms have been described. In most of these models, the quantiication of biofilm is done by conventional plating ater disruption of the biofilm. hese methods are labour-intensive and slow, and the process of disrupting the biofilm can be incomplete or kill cells so that, the number of colonies does not necessarily relect the number of viable bacteria in the biofilm. Indirect methods are based on quantiication of biomass (both living and dead cells), viability assays (living cells) and matrix quantiication [4]. Many studies have now demonstrated that biofilm-producer microorganisms have an inherent lack of susceptibility to antibiotics, whereas planktonic cultures of this same organism do not. his resistance is lost once the biofilm is reverted to conditions that permit planktonic growth [5]. he innate resistance of microbial biofilms to antibiotic therapy has led to problems in their eradication and in the management of patients with device related infections. Biofilms may also interfere with the immune clearance of infectious agents. his diference in antibiotic susceptibility between planktonic and biofilm populations of the same organism may result from diferences in the difusion of antibiotics or much more complex changes in the microbial physiology of the biofilm. he concentrations of antibiotics needed to inhibit bacterial growth in the sessile phase are oten much higher than those required for bacteria in the planktonic phase [6]. *Corresponding author: Dr. Nahla A Melake, Department of Pharmaceutics, Faculty of Pharmacy, King Saud University, Saudi Arabia, Tel: +966-1-2913735; E-mail: nmelake@ksu.edu.sa Received March 13, 2012; Accepted June 21, 2012; Published June 23, 2012 Citation: Mahmoud HA, Melake NA, El-Semary MT (2012) Bactericidal Activity of Various Antibiotics versus Tetracycline-loaded Chitosan Microspheres against Pseudomonas aeruginosa Bioilms. Pharmaceut Anal Acta S15. doi:10.4172/2153- 2435.S15-007 Copyright: © 2012 Mahmoud HA, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract The discovery of bioilms in 1980’s has brought much interest to the study of the contribution of bacterial bioilms 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) bioilms. P. aeruginosa isolates were collected and identiied using standard methods. A modiied microtiter plate test was used to determine the bioilm-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 eficient bioilm producer-strains. There were differences in the antibiotic susceptibility of planktonic and sessile cell populations. Fluoroquinolones, aminoglycoside and tetracycline showed more potent activity (MIC 50 was 0.8, 4.88 and 34.19 μg/ml, respectively) than penicillin, cephalosporin, clarithromycin and macrolides. Bioilm 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 irst 6 h and continued for 24 h. This in the clinical ield 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 speciic drug delivery system to increase the eficacy of tetracycline against bioilm-associated P. aeruginosa infections. However, it would be appropriate to conduct clinical studies to conirm this. Bactericidal Activity of Various Antibiotics versus Tetracycline-loaded Chitosan Microspheres against Pseudomonas aeruginosa Biofilms Hanaa A Mahmoud 1 , Nahla A Melake 1,2 * and Mona T El-Semary 1 1 Department of Pharmaceutics, Faculty of Pharmacy, King Saud University, Saudi Arabia 2 Department of Medical Microbiology and Immunology, Faculty of Medicine, Menuiya University, Egypt