Environmental reservoirs of carbapenem-resistant organisms in the intensive care unit: a multicenter longitudinal study in two middle-income country hospitals

BACKGROUND: There is limited data regarding environmental reservoirs of carbapenem-resistant organisms (CRO) during non-outbreak settings in resource-limited hospitals, or the role of these reservoirs in healthcare transmission. METHODS: Prospective longitudinal study in which sinks and high-touch surfaces (HTS) were sampled prior to room cleaning in intensive care units (ICUs) in two hospitals (hospital A, Argentina, and hospital B, India), July 2023-February 2024. Selective media was used to recover CROs. Whole genome sequencing (WGS) and single nucleotide polymorphism (SNP) pairwise analysis were performed on environmental and clinical isolates to evaluate bacterial transmission dynamics. Metagenomic sequencing was performed to evaluate bacterial diversity of environmental samples. RESULTS: Of 541 environmental samples collected, 47.9% in hospital A and 97.5% in hospital B grew at least one CRO. Most CROs tested for the presence of a carbapenemase were positive (63.9-91.0% for hospital A and B isolates, respectively). Carbapenemase producer (CP)-Acinetobacter baumannii and CP-Pseudomonas spp. predominated in HTS and sinks samples, respectively, in hospital A; while CP-Klebsiella pneumoniae predominated in hospital B samples. WGS of 113 CRO isolates and SNP analysis demonstrated certain lineages established enduring reservoirs in the ICUs environment (e.g., blaVIM-36 P. aeruginosa ST395 isolates with 2-9 SNP difference were detected in sinks over 7 months). Several clusters involving environmental and clinical isolates that shared an epidemiological link and displayed ≤ 10 SNP difference were identified (e.g., blaOXA-23 A. baumannii ST195 isolated from three unique patients who stayed in the same private room on sampling months 4, 5, 6 and 7, and from HTS of that room on sampling month 5 displayed 0-3 SNP difference). Metagenomic analysis identified additional AMR genes of clinical importance. CONCLUSIONS: CROs were abundant and persisted in the ICU environment in countries with high prevalence of MDROs. Our data suggests movement of clones between the environment and patients.