Multidrug-resistant Pseudomonas aeruginosa in immunocompromised cancer patients: epidemiology, antimicrobial resistance, and virulence factors.

This study explores the antimicrobial resistance patterns and virulence properties of Pseudomonas aeruginosa obtained from blood samples of febrile immunocompromised patients. Fifty-two clinical isolates were examined for demographic and clinical characteristics, antimicrobial resistance profiles, and different virulence factors. Antimicrobial susceptibility testing and qualitative detection of efflux pump activity, biofilm formation, pigment production, and swarming motility were evaluated. The pathogenic potential of the isolates was assessed using the Galleria mellonella infection model. All isolates exhibited MDR, XDR, and PDR phenotypes. The crude 30-day mortality rate was 26.9%, with higher mortality detected in infections due to XDR strains. Colistin, aztreonam, and ceftolozane/tazobactam demonstrated the best susceptibility rates. Metallo-β-lactamase NDM−1 was the most frequently detected gene in our isolates. Efflux pump activity was significantly associated with higher MICs. Biofilm formation was predominant, with moderate to strong biofilm formers showing reduced antibiotic susceptibility. Swarming motility is associated with urinary tract infections. The Galleria mellonella model demonstrated higher lethality for isolates originating from respiratory tract infections. This study highlights the escalating load of antimicrobial resistance and significant virulence of P. aeruginosa which directly affects the available treatment strategies. The use of the relatively novel ceftolozane/tazobactam combination is threatened due to the high levels of blaNDM−1 producers detected. Colistin and Aztreonam are still offered treatment options. Clinical trial number: Not applicable.