Virulence arsenal and antibiotic resistance backgrounds in Pseudomonas aeruginosa isolates from hospital wastewater samples from Iraq.

BACKGROUND: The aim of the study was to examine the antibiotic resistance patterns and virulence factors in Pseudomonas aeruginosa isolates in hospital wastewater (HWW). METHODS: A total of 155 HWW samples were investigated in Babylon city, Iraq (December 2025 to June 2026). Cellulose ester membrane filters were used to pass the HWW samples. These filters were grown in cetrimide agar. The suspected green colonies of P. aeruginosa species were further determined using a VITEK2 device. Confirmation of the P. aeruginosa isolates was performed through polymerase chain reaction (PCR) of ecfX gene. Disc diffusion testing was used for antibacterial susceptibility. PCR was used to assess the presence of lasA, lasB, toxA, exoS, exoT, exoU, exoY, plcH, plcN, phzI, phzII, apr, algD, and algU virulence genes. RESULTS: Totally, 119 P. aeruginosa isolates were collected. These isolates showed a high resistance to aztreonam (65.5%) and ceftazidime (58.8%). However, colistin was highly effective (89.9% susceptible). Occurrence of multidrug-resistant (MDR) isolates was 82.4% (n = 98/119). The most prevalent genes were toxA (100.0%), lasB (65.5%), and exoT (65.5%). Significant positive correlations have been found among the following pairs: algU and ciprofloxacin; phzII and piperacillin; phzI and imipenem, ceftazidime, amikacin; plcN and imipenem; plcH and amikacin, piperacillin, piperacillin/tazobactam; exoY and piperacillin; exoT and ceftazidime; and exoS and colistin. CONCLUSION: The most P. aeruginosa isolates possessed toxA and lasB genes. The results indicated that hospital effluents are critical sources of MDR and virulent P. aeruginosa, and there is an urgent demand to improve the management of wastewater.