High Incidence of MDR and XDR Pseudomonas aeruginosa Isolates Harboring blaGES, blaVEB, and blaPER Extended-Spectrum Beta-Lactamase Genes in Iran

The ever-increasing incidence of multidrug resistance in ESBL-producing Pseudomonas aeruginosa is one of the most serious public health threats. This study aimed to investigate the antibiotic resistance profile and molecular characteristics of ESBL-producing P. aeruginosa isolates.

Antimicrobial susceptibility testing was performed for 120 P. aeruginosa clinical isolates using the Kirby-Bauer disk diffusion and broth microdilution assays. Combined disk test (CDT) was applied to screen for ESBL production among P. aeruginosa isolates. PCR assays determined the presence of blaGES, blaPER, and blaVEB genes in all isolates.

The clinical isolates of P. aeruginosa showed the highest resistance to cefotaxime (86.7%) and gentamicin (65.8%). Of 120 P. aeruginosa isolates, 60.8% were MDR, and 53.3% were XDR. The prevalence of these strains was significantly higher in hospitalized patients than in out-patients (p<.001). Also, 58 P. aeruginosa strains (48.3%) were considered as phenotypic ESBL producers. Furthermore, 15, 35, and 24.2% of P. aeruginosa isolates harbored blaGES, blaVEB, and blaPER, respectively. The incidence of MDR (71.4% vs. 41.9%, p= .001) and XDR (63.6% vs. 34.9%, p= .002) was significantly higher in ESBL-producing P. aeruginosa isolates compared to non-ESBL producers. The highest incidence rate of MDR was reported in blaVEB gene-positive P. aeruginosa isolates (95.2%), followed by isolates harboring blaPER (79.3%) and blaGES (55.6%) genes.

This study findings show a high prevalence of MDR ESBL-producing P. aeruginosa isolates, indicating the importance of correct identification of these superbugs and judicious use of various antibiotics to prevent their spread.