Complex Interplay between Biofilm Formation, Antibiotic Resistance, and Virulence in Pseudomonas aeruginosa: A Phenotypic and Genotypic Study

This study investigated the relationship between biofilm formation, virulence, and antibiotic resistance in Pseudomonas aeruginosa. We analyzed 84 clinical isolates for antimicrobial resistance (AMR), virulence, and biofilm-related genes (algR, lecA, pelA, and pslA) using RT-PCR. The expression of biofilm-related genes was further evaluated by quantitative RT-PCR. Antimicrobial tests revealed high proportions of multidrug-resistant MDR (20.24%), extensively drug-resistant XDR (17.86%), and pan drug-resistant PDR (1.19%) isolates. Biofilm formation was prevalent, with 95.29% of isolates producing biofilms: 14.12% were strong producers, 43.53% were moderate, 37.64% were weak, and 4.71% non-producers. Molecular analysis identified a high prevalence of biofilm-related genes (algR, lecA, pelA, and pslA) and virulence genes (aprA, exoS, exoT, and toxA), while resistance genes blaNDM and blaIMP were detected less frequently. Efflux pump genes (mexD, mexF, and mexY) showed co-occurrence. Strong biofilm production was positively correlated with colistin sensitivity but negatively correlated with resistance to levofloxacin and ciprofloxacin. Strong positive correlations were also found between lecA, pelA, and pslA, indicating potential co-regulation. lecA expression was significantly correlated with biofilm strength, whereas other biofilm-related genes showed weaker relationships, suggesting a complex regulation among biofilm genes. Our findings indicate that, although biofilm strength, virulence, and resistance are closely interlinked, considerable variability persists in both biofilm production and its associations. These findings highlight the need for future research to integrate phenotypic, genetic, and regulatory analyses to effectively fight against P. aeruginosa infection.