An unusual multidrug-resistant bacterium lurked in sinks at the National Institutes of Health’s Clinical Center for more than a decade, striking at least a dozen patients, a new report by NIH scientists concludes.

Researchers tracked the superbugs to sinks in patient rooms amid a freaky outbreak in 2016. Searching through genetic sequences of clinical samples collected as far back as 2006—a year after a new inpatient hospital building opened—researchers identified eight other cases for a total of 12 instances where the sink-dwelling germs had splashed into patients.

The aquatic germ in these cases was Sphingomonas koreensis. Such sphingomonas species are ubiquitous in the environment but rarely cause infections. In the NIH patients, however, they were found to cause a variety of problems, including pneumonia, blood infections, a surgical site infection, and a potential urinary tract colonization. Some isolates were resistant to 10 antibiotics tested, spanning three classes of drugs.

Three of the 12 affected patients died following their infection. However, they were all also suffering from severe, unrelated infections prior to exposure to the sink-based germs, the NIH researchers note.

Their report, published recently in the New England Journal of Medicine , highlights the murky problem of opportunistic, often drug-resistant pathogens endangering vulnerable patients by lurking in hospitals—and hospital sinks in particular. As Ars has reported before, superbug-spewing sinks have been fingered in a variety of hospital outbreaks over the years. In 2017, researchers published a splashy study showing that dangerous germs can survive in sink P-traps , climb plumbing using creeping films, and launch up onto touchable surfaces with a blast from the faucet.

However, that particular plumbing peril wasn’t the problem in the NIH’s case. After surveying a variety of potential sources, including ice machines and the municipal intake pipe for the hospital, researchers found the germs skulking in sink faucets and fixtures—not sink drains.

Disassembling infected sinks, researchers found S. koreensis inhabiting nine plumbing parts, including the faucet, aerators, and mixing valves. The researchers had several faucets replaced, only to find that they were recolonized shortly after, likely via shared contaminated water supply pipes between sinks. Ultimately, the researchers appeared to rid the sinks of the dangerous interlopers by upping the hot water temperature and chlorine concentrations for the hospital.

In all, the researchers suspect that “a single S. koreensis strain entered the water system soon after construction of the new NIH Clinical Center hospital building in 2004” and colonized pipes before the hospital opened, while water in the plumbing was stagnant. Then, the germ “disseminated throughout the hospital and diversified at multiple distinct locations,” causing a sporadic, decade-long clonal outbreak.

The outbreak isn’t the first for the NIH’s unique clinical research center, which aims to treat rare and intractable illnesses with innovative medicine. In 2011, the center was struck with an outbreak of another superbug, carbapenem-resistant K. pneumoniae, which affected 18 patients, 11 of whom died. A case of fungal contamination at the hospital in 2015 prompted a leadership overhaul. An independent review had determined that patient safety at the hospital had become “subservient to research demands.”

Yet, the authors of the new study note that the threat of S. koreensis is not unique to the NIH’s hospital, regardless of its struggles. And they note that the “steps taken in this study to prevent further S. koreensis infections within the NIH Clinical Center are applicable to many opportunistic waterborne pathogens.”

New England Journal of Medicine, 2018. DOI: 10.1056/NEJMoa1803238 (About DOIs).