Retrospective genome-oriented analysis reveals low transmission rate of multidrug-resistant Pseudomonas aeruginosa from contaminated toilets at a bone marrow transplant unit.

BACKGROUND

Prevention of toilet-to-patient transmission of multidrug-resistant Pseudomonas aeruginosa (MDR PA) poses management-related challenges at many bone marrow transplant units (BMTU). Using whole-genome sequencing (WGS), we conducted a longitudinal retrospective analysis of the toilet-to-patient transmission rate for MDR PA under existing infection control (IC) measures at a BMTU with persistent MDR PA toilet colonization.

METHODS

The local IC bundle comprised 1.) patient education regarding IC, 2.) routine patient screening, 3.) toilet flushing volume of 9L, 4.) bromination of toilet water tanks, and 5.) toilet decontamination using hydrogen peroxide. Toilet water was sampled periodically between 2016-2021 (minimum every three months - 26 intervals). Upon MDR PA detection, disinfection and re-sampling were repeated until ≤ 3 cfu/100ml was reached. WGS was performed retrospectively on all available MDR PA isolates (90 of 117 positive environmental samples, 10 of 14 patients - including nine nosocomial).

RESULTS

WGS of patient isolates identified six sequence types (STs), with ST235/CT1352/FIM-1 and ST309/CT3049/no-carbapenemase being predominant (three isolates each). Environmental sampling consistently identified MDR PA ST235 (65.5% ST235/CT1352/FIM-1), showing low genetic diversity (difference of ≤29 alleles by cgMLST). This indicates that direct toilet-to-patient transmission was infrequent although MDR PA was widespread (detection on 79 occasions, detection in every toilet). Only three MDR PA patient isolates can be attributed to the ST235/CT1352/FIM-1 toilet MRD PA population over six years.

CONCLUSIONS

Genome-oriented environmental and patient surveillance suggests that the persistent presence of MDR PA poses a potential risk for acquisition, but with stringent targeted toilet disinfection, only three highly vulnerable patients experienced nosocomial transmission.

Informations de copyright

Copyright © 2024. Published by Elsevier Ltd.

Déclaration de conflit d'intérêts

Declaration of Competing Interest All authors declare that they have no conflict of interest.