T3SS virulence factors and antimicrobial resistance of Pseudomonas aeruginosa isolated from medical devices of Peruvian inpatients in critical care units

Pseudomonas aeruginosa is an opportunistic Gram-negative bacteria identified as the main cause of serious nosocomial infections in Peru, especially in vulnerable patients, such as those hospitalized in critical care units (CCUs). Often, these infections are difficult to treat due to high antimicrobial resistance, enhanced virulence causing greater damage to the host, a tendency towards chronicity, and increases the risk of mortality. Thus, surveillance of this species in the aforementioned wards is encouraged.

Between July and September 2025, we collected the following medical devices, vascular catheters (VCs), urinary catheters (UCs), and endotracheal tubes (ETTs), from adult patients hospitalized in the CCU of a level-III reference hospital. Forty-two Pseudomonas aeruginosa isolates from different devices were recovered from MacConkey Agar and confirmed by PCR. Antimicrobial susceptibility was performed by disk diffusion using CLSI 2025 guidelines. Type 3 Secretion system virulence factor genes (T3SS) were detected by PCR, as well as carbapenemase genes bla_VIM, bla_IMP, bla_NDM and bla_KPC.

Out of 42 strains of P. aeruginosa from medical devices, 76% (32/42) were carbapenem-resistant; bla_IMP was identified in 12/32 isolates and bla_VIM in 5/32, the latter being VIM/IMP co-producers. The bla_KPC gene was found in 6/32 isolates and none carried bla_NDM. Regarding T3SS, we found the presence of exoU (15/42) and exoS (30/42), with three isolates being exoU+/exoS+. Most isolates also carried exoY (42/42) and exoT (39/42).

These results showed high carbapenem resistance in P. aeruginosa isolated from medical devices at a III-level Peruvian hospital and shed light on its T3SS virulence factors.Similar molecular epidemiology studies should be replicated.