High virulence and genetic heterogeneity in Pseudomonas aeruginosa isolates from lower respiratory tract infections in neutropenic patients

The aim of this study was to determine the antimicrobial susceptibility, virulence genotypes, presence of extended spectrum β-lactamase (ESBL) and carbapenemase genes, and clonality of Pseudomonas aeruginosa isolates responsible for lower respiratory tract infections in patients admitted to the National Bone Marrow Transplant Center (NBMTC) of Tunisia. During the 11-year study period, a total of 50 P. aeruginosa isolates were responsible for lower respiratory tract infections. Isolates were studied by determining their serotypes, antimicrobial susceptibility, genes encoding ESBL/carbapenemases and virulence factors, and genetic relatedness by ERIC-PCR. High to moderate resistance rates were observed for ticarcillin, ticarcillin-clavulanic acid, piperacillin-tazobactam, ceftazidime, cefepime, imipenem, meropenem, ciprofloxacin, amikacin, and fosfomycin. One isolate showed an ESBL phenotype encoded by the bla_SHV-2a gene. Of 13 isolates resistant to both imipenem and meropenem, the bla_GES gene was amplified in nine isolates. Isolates exhibited 19 virulence genotypes, of which five were prevalent: V1 (14 genes; n=14), V2 (14 genes, n=6), V3 (all genes, n=6), V4 (13 genes, n=5), and V5 (13 genes, n=5). ERIC-PCR showed high genetic heterogeneity. These findings highlight the high genetic heterogeneity of P. aeruginosa isolates in these neutropenic patients, as well as their remarkable pathogenic power, raising significant concern.