Navid Saidi - Molecular Microbiology Research Center (MMRC), Shahed University, Tehran, Iran
Saied Besharati - Department of Microbiology, Faculty of Medicine, Shahed University, Tehran, Iran
Horieh Saderi - Molecular Microbiology Research Center (MMRC), Shahed University, Tehran, Iran
Parviz Owlia - Molecular Microbiology Research Center (MMRC), Shahed University, Tehran, Iran

Introduction and Objectives: P. aeruginosa is one of the most common opportunistic bacteria in nosocomial infections, which has a significant resistance to antimicrobial agents. P. aeruginosa is a biofilm‐forming bacterium which can result in serious health problems. The purpose of this study was to investigate the biofilm formation, alginate production and antimicrobial susceptibility patterns among P. aeruginosa isolated from respiratory tract specimens. Materials and Methods: In this study, 36 isolates of P. aeruginosa were recovered from respiratory tract specimens. P. aeruginosa isolates were identified and confirmed by phenotypic methods and PCR test. Antimicrobial susceptibility of the isolates has been specified by the disk diffusion method. Biofilm formation and alginate production of these isolates were measured by microtiter plate and carbazole assay, respectively. Results: Antimicrobial susceptibility test showed that 12 (33.3%) isolates were sensitive to all antibiotics; on the other hand, 4 (11.1%) isolates were resistant to all antibiotics. 11 (30.5%) of P. aeruginosa isolates were multidrug-resistant (MDR). The most effective antibiotic was piperacillin-tazobactam as 83.3% of isolates were sensitive, and the most resistant was observed for ofloxacin (36%). All isolates were biofilm and alginate producers, in which, 36.1% were strongly biofilm producers, and the rates of moderate and weak biofilm producers were 52.8% and 11.1%, respectively. The production of alginate in 93% of strong-biofilm forming isolates was more than 250 μg/ml, while 75% of low-biofilm forming isolates produced less than 250 μg/ml alginates. Conclusion: In this study, a high prevalence of biofilm and alginate production was observed in P. aeruginosa isolates from respiratory tract specimens. Also, the results of this study indicated a relationship between the rate of alginate production and level of biofilm formation in P. aeruginosa isolates.

Alginate, Biofilm, Pseudomonas aeruginosa