The Burden of Antimicrobial-Resistant Pseudomonas aeruginosa Isolates in Children With Cystic Fibrosis: Molecular Characterization and Genotyping Analysis.

Pseudomonas aeruginosa poses a significant therapeutic challenge in pediatric patients with cystic fibrosis (CF) due to increasing multidrug resistance (MDR) and carbapenem resistance, underscoring the need for surveillance to guide treatment strategies. In this study, sputum and throat swab samples were collected from inpatient and outpatient CF children with pulmonary infection at the Children's Medical Center in Tehran, Iran. Isolates were identified using standard culture and biochemical methods, followed by antimicrobial susceptibility testing. Carbapenemase production was assessed phenotypically and by molecular detection of resistance genes, and genetic diversity was also evaluated using Random Amplified Polymorphic DNA (RAPD)-polymerase chain reaction (PCR). A total of 117 P. aeruginosa isolates were recovered (prevalence 17.41%), of which 94.9% were nonsusceptible to at least one antimicrobial agent. Carbapenem-resistant P. aeruginosa (CRPA) and MDR isolates accounted for 24.8% and 23.1% of isolates, respectively. Carbapenemase gene coexistence was significantly associated with MDR (ρ = 0.227, p = 0.014) and CRPA (ρ = 0.314, p = 0.001). Metallo-β-lactamase production was detected in 13.7% of isolates, while blaVIM was the most frequently identified carbapenemase gene (59%). RAPD-PCR demonstrated marked genetic heterogeneity, grouping isolates into 24 distinct clusters. Overall, the substantial burden of MDR and CRPA identified at this tertiary pediatric center highlights an urgent need for stricter antimicrobial stewardship, enhanced infection control measures, and ongoing surveillance to mitigate resistance spread and preserve therapeutic effectiveness in this vulnerable population. These findings warrant multicenter investigation to determine whether similar patterns exist across other Iranian pediatric CF facilities.