The impact of an intervention to reduce dispersal from wastewater drain sites on carbapenem-resistant Pseudomonas aeruginosa colonization and bloodstream infection on a hematopoietic cell transplant and hematologic malignancy unit

Objective: To evaluate the impact of an intervention to limit dispersal from wastewater drain (WWD) sites on meropenem-nonsusceptible Pseudomonas aeruginosa patient and environmental colonization and bloodstream infection (BSI) on a hematopoietic cell transplant (HCT) and hematologic malignancy (HM) unit. Design: This quasi-experimental study included pre/postintervention point-prevalence surveys in July 2019 and June 2020, respectively. The retrospective cohort included HCT/HM patients with P. aeruginosa BSI between 2012 and 2022. Setting: Adult HCT/HM unit at an academic center. Participants: This study included consenting HCT/HM patients on the unit at the time of the point-prevalence surveys. HCT/HM patients with P. aeruginosa BSI between 2012 and 2022. Methods: A quality improvement intervention targeting WWD sites was conceived and implemented on a HCT/HM unit. Pre and postintervention colonization samples were obtained from patients and environmental sites, cultivated on selective media, then characterized by susceptibility testing. Whole-genome sequencing and phylogenetic analysis were performed on select isolates. The impact of the intervention on colonization and BSI was evaluated, as was relatedness among isolates. Results: Although colonization of WWD sites with meropenem-nonsusceptible P. aeruginosa was widespread before and after this intervention, we observed a substantial decline in patient colonization (prevalence rate ratio, 0.35; 95% confidence interval [CI], 0.04-3.12) and BSI (incidence rate ratio, 0.67; 95% CI, 0.31-1.42) after the intervention. Among 3 predominant sequence types (ST-111, ST-446, and ST-308), there was striking genetic conservation within groups and among environmental colonization, patient colonization, and BSI isolates. Conclusions: An intervention targeting WWD sites on a HCT/HM unit had a meaningful impact on meropenem-nonsusceptible P. aeruginosa patient colonization and BSI.