Iranian Journal of Medical Microbiology

Background and Aims: Pseudomonas aeruginosa (P. aeruginosa) is a Gram-negative bacterium that causes lung infections in cystic fibrosis (CF) patients by forming biofilms, which contribute to antibiotic resistance. The genetic diversity among strains could be important epidemiologically in the community of CF patients. This study investigated P. aeruginosa strains from CF patient sputum, focusing on their antibiotic resistance, biofilm production, and genetic diversity to understand their epidemiological relations.
Methods: Sixty-five strains of P. aeruginosa were isolated from CF patients with pulmonary infection symptoms (October 2023 to October 2024) at Imam Khomeini Children's Hospital in Tehran when the patients were admitted to the hospital. The antibiotic susceptibility patterns of these strains were examined using the disk diffusion method (Kirby-Bauer), based on the CLSI standard. Moreover, to evaluate colistin susceptibility, the broth microdilution (BMD) method was used. The strains' ability to produce biofilms was evaluated using a microtiter plate (MTP) assay. Finally, RAPD-PCR (Random Amplified Polymorphic DNA- Polymerase Chain Reaction) was employed for genetic analysis, using the short primer 272.
Results: 61.53% of P. aeruginosa strains exhibited MDR (Multidrug-Resistance), while 30.7% of the strains exhibited XDR (Extensively drug-resistant) characteristics. The highest levels of antibiotic resistance were found against amoxicillin, amikacin, and Cefepime. XDR and MDR strains exhibited a strong biofilm-forming ability. The 65 studied strains were classified into 19 groups based on RAPD-PCR patterns, with six strains sharing similar genetic traits divided into four categories.
Conclusion: The study showed a rise in antibiotic resistance in P. aeruginosa and established a strong connection between biofilm production and resistance. Some isolates exhibited similar genetic patterns, indicating possible cross-infection.