Biofilm and Antimicrobial Resistance of Clinical and Environmental Isolates of Pseudomonas aeruginosa

Objectives: To evaluate the clinical and environmental ability of P. aeruginosa isolates to make biofilms and to determine their antimicrobial susceptibility patterns. Methods: Environmental swabs (144), air (28) and water samples (12) were collected from various wards of Gaza strip hospitals. Additionally, 158 clinical P. aeruginosa isolates were obtained from the microbiology laboratories of the same hospitals between July 21, 2019 and January 21, 2020. Samples were cultured and bacterial identification was performed using standard microbiological procedures. PCR was used to confirm the identity of P. aeruginosa. P. aeruginosa isolates were tested for their antimicrobial susceptibility patterns by the agar disk diffusion method. Both qualitative and quantitative methods assessed the biofilm formation by crystal violet and safranin stains. Results: Among the P. aeruginosa isolates (N=150), 90.0% were resistant for ceftazidime, (36.7%) aztreonam, (29.3%) gentamicin, (27.3%) levofloxacin, (22.0%) meropenem, (14.0%) piperacillin, (10.0%) amikacin and (9.3%) imipenem. The results for biofilm formation by tube method showed that 78.0% and 71.3% of the isolates were biofilm producer by crystal violet and safranin methods, respectively. Microtiter plate method demonstrated that 94.0% and 96.0% were biofilm producers by crystal violet and safranin, respectively. In addition, there was a statistical significance between the meropenem resistance and biofilm-forming ability of the isolates. Conclusions: High resistance rates were detected among P. aeruginosa isolates. The lowest rate of resistance was to imipenem and amikacin. As for the biofilm assessment, the tissue culture plate method showed higher detection rates than the tube method.