Recurrent Outbreak of Carbapenem-Resistant IMP-1-Producing Pseudomonas aeruginosa in Kidney Transplant Recipients: The Impact of Prolonged Patient Colonization.

Background: Infections by carbapenem-resistant Pseudomonas aeruginosa (CRPA) have been associated with high morbidity and mortality among solid organ recipients.

Objectives: To delineate the epidemiological and molecular characteristics of a recurrent outbreak of imipenem (IMP)-producing P. aeruginosa (CRPA) among kidney transplant (KT) recipient METHODS: We described a recurring CRPA outbreak in a KT ward, divided into two periods: before unit closure (Feb 2019-2020) and after reopening (Aug 2020-Dec 2023). Routine surveillance cultures (SCs) were performed using axillary-perineum-rectal swabs with immunochromatographic tests. A case-control study identified risk factors for CRPA acquisition. Pulsed-field gel electrophoresis and whole genome sequencing characterized the strains.

Results: After reopening, new cases arose from patients previously colonized, peaking 18 months later. A total of 67 KT recipients with CRPA-IMP-producing strains were identified. All except one sequenced strain belonged to the ST446 clone, differing by a maximum of 110 single nucleotide polymorphisms. Forty-five (67.2%) cases were identified through SC, with 45.7% showing intermittent SC positivity. Patients remained colonized for up to 623 days. Twenty-four (35.8%) patients had infections, with the most common site being the urinary tract. Identified risk factors included older age, deceased donor, re-transplantation, reoperation, carbapenem or quinolone use, lymphopenia, hospital stay >10 days, and the first 60 days post-KT.

Conclusion: KT recipients can harbor CRPA for extended periods, and detecting CRPA-colonized patients is challenging. These characteristics highlight the patient as the major source and a critical point in outbreak control.