A rare waterborne pathogen was identified in a cluster of healthcare-associated infections (HAIs) at one hospital, and was found in the hospital’s plumbing system, researchers found.
Genetically similar variations of Sphingomonas koreensis were identified in four of six sphingomonas infections in one hospital in 2016, reported Julia A. Segre, PhD, of the National Human Genome Research Institute of the National Institutes of Health (NIH) in Bethesda, Maryland, and colleagues.
This led to both an investigation of sphingomonas cases at the hospital over a decade, as well as a more thorough examination of the hospital water system — where the pathogen was identified in sinks and faucets of the prior rooms of patients with these infections, the authors wrote in the New England Journal of Medicine.
However, the authors noted that they were unable to match any isolate from a sink in a patient room to a clinical isolate, which they cited as a limitation to their findings.
S. koreensis is a waterborne organism, which also poses risk for HAIs, particularly in immunocompromised patients, they said. Exposure is through water droplets or water aerosols “that are inhaled or that breach normal defenses through non-intact mucous membranes or invasive devices,” the authors said. They added that community-acquired sphingomonas infections are rarely reported.
In this study, researchers first examined a cluster of sphingomonas infections over a 6-month period in six patients at the NIH Clinical Center, and found that isolates from four of six patients were identified as multi-drug resistant S. koreensis, which was “previously reported in only two clinical cases,” they said.
Researchers performed whole-genome DNA sequencing on isolates of multi-drug resistant S. koreensis that were identified from 2006 to 2016, the authors said.
They then reviewed patient records for potential common sources of exposure, including “hospital rooms, wards, invasive procedures, dialysis, respiratory treatments and therapeutic baths.” They cultured potable water, sink faucets, ice machines, and other plumbing components, as well as samples from water and faucets in rooms of inpatients with S. koreensis infections. Researchers also took “large-volume water samples,” including from the pipes that supplied rooms found to have culture-positive sinks.
From 2006 — the year that a new inpatient building was opened — to 2016, they identified S. koreensis clinical isolates in 12 patients. All patients were hospitalized at the time of their positive cultures — five in the intensive care unit and seven in other wards. Median length of stay was 44 days before a positive culture. While four patients had a single positive culture, the others had “persistent or recurrent” positive cultures from two to 43 days, the authors said.
Of these 12 patients, nine were stem-cell transplant recipients. There were eight with S. koreensis bacteremia, including two with “concurrent S. koreensis pneumonia and three with catheter-related bloodstream infections.”
One patient had S. koreensis cultured from urine, and the organism was believed to “represent contamination or colonization.” Of the remaining 11, there were eight patients who recovered, and three who died. The authors noted these three patients all had S. koreensis sepsis as well as “severe, unrelated infections.”
They found S. koreensis in 39% of faucets and 53% of water samples from patient rooms. Notably, they found “isolates derived from sink components and water samples were genetically related to the S. koreensis isolates obtained from patients in 2016 (>99.7% average nucleotide identity).” They added that this “implicated sinks or water as the most likely source of nosocomial S. koreensis infections.”
However, the authors found that while the bacteria was cultured from water in patient rooms, it was not detected in “municipal water entering the hospital, in water sampled from the large pipes branching off the main intake pipe, or in ice machines.”
Interestingly, the authors found that three distinct isolates were identified from a single sink faucet, and two of those strains were detected even 4 months after the faucet was replaced, “which suggested recolonization of the new faucet by a proximal reservoir.”
Components of serially infected faucets were immersed in 71° C (approximately 160° F) water baths for 20 minutes, and subsequent cultures were negative. The authors also noted that “aerators were removed from affected sinks” and “no further S. koreensis infections have occurred since the augmentation of free chlorine concentrations and the adjustment of hot-water temperature in December 2016.”
This study was supported by the NIH Intramural Research Programs, including the National Human Genome Research Institute, the NIH Clinical Center, and the National Institute of Allergy and Infectious Diseases.
The authors disclosed no conflicts of interest.