Multicenter Outbreak of Gram-Negative Bloodstream Infections in Hemodialysis Patients.

Rationale & objective: Contaminated water and other fluids are increasingly recognized to be associated with health care-associated infections. We investigated an outbreak of Gram-negative bloodstream infections at 3 outpatient hemodialysis facilities. Study

Design: Matched case-control investigations. Setting & participants: Patients who received hemodialysis at Facility A, B, or C from July 2015 to November 2016. Exposures: Infection control practices, sources of water, dialyzer reuse, injection medication handling, dialysis circuit priming, water and dialysate test findings, environmental reservoirs such as wall boxes, vascular access care practices, pulsed-field gel electrophoresis, and whole-genome sequencing of bacterial isolates. Outcomes: Cases were defined by a positive blood culture for any Gram-negative bacteria drawn July 1, 2015 to November 30, 2016 from a patient who had received hemodialysis at Facility A, B, or C. Analytical approach: Exposures in cases and controls were compared using matched univariate conditional logistic regression.

Results: 58 cases of Gram-negative bloodstream infection occurred; 48 (83%) required hospitalization. The predominant organisms were Serratia marcescens (n=21) and Pseudomonas aeruginosa (n=12). Compared with controls, cases had higher odds of using a central venous catheter for dialysis (matched odds ratio, 54.32; lower bound of the 95% CI, 12.19). Facility staff reported pooling and regurgitation of waste fluid at recessed wall boxes that house connections for dialysate components and the effluent drain within dialysis treatment stations. Environmental samples yielded S marcescens and P aeruginosa from wall boxes. S marcescens isolated from wall boxes and case-patients from the same facilities were closely related by pulsed-field gel electrophoresis and whole-genome sequencing. We identified opportunities for health care workers' hands to contaminate central venous catheters with contaminated fluid from the wall boxes. Limitations: Limited patient isolates for testing, on-site investigation occurred after peak of infections.

Conclusions: This large outbreak was linked to wall boxes, a previously undescribed source of contaminated fluid and biofilms in the immediate patient care environment.