Phenotypic and genotypic characterization of clinical Pseudomonas aeruginosa

Abstract

Objectives: Pseudomonas aeruginosa is an opportunistic pathogen that can cause many nosocomial infections. Biofilm formation, drug resistance, and motility contribute to virulence in P. aeruginosa. This study assessed the colistin minimum inhibitory concentration (MIC), biofilm formation, presence of mod A and psl A genes, and types of motilities in multidrug-resistant (MDR) and multidrug-susceptible (MDS) P. aeruginosa. Methods: Sixty-two P. aeruginosa from pus and 18 from urine samples were studied for their susceptibility to commonly used antibiotics, colistin MIC by agar dilution, and biofilm-forming ability by the microtiter plate method. All MDR and MDS P. aeruginosa isolates were tested for the presence of mod A and psl A genes by PCR, and different types of motilities using specific media. Results: Among the 40 MDR and 40 MDS isolates, 17 each were colistin-resistant and 23 each were colistin-intermediate. Nine MDR pus isolates and three MDR urine isolates showed all three types of motilities. Thirteen MDS pus isolates and four MDS urine isolates showed both swimming and swarming motility. MDS isolates did not show twitching motility. A higher number of MDR strains were strong biofilm producers (n ¼ 19), whereas a higher number of MDS strains (n ¼ 24) were moderate biofilm producers (p ¼ 0.023). Twenty-seven MDR and twenty-eight MDS isolates were positive for both mod A and pslA genes. Among the strong biofilmforming pus isolates, a greater number of MDR isolates (n ¼ 13 each) had modA and pslA genes compared to MDS isolates (modA p ¼ 0.017; pslA p ¼ 0.014). Conclusions: Our findings clearly showed a statistically significant association among strong biofilm formation, modA, pslA genes, and drug resistance in P. aeruginosa isolated from clinical samples. Additional studies are needed to explore other genes and factors responsible for weak and moderate biofilm formation and drug resistance.