An investigation aimed at pinpointing the source of a lingering bacterial outbreak in a Toronto hospital turned up an unlikely suspect.

The sinks did it.

State-of-the-art hand washing sinks installed in the intensive care unit and some patient rooms in Toronto's Mount Sinai Hospital actually became the reservoir of a pesky drug-resistant bug that infected or colonized 66 patients from the fall of 2006 to the spring of 2011.

Researchers from the hospital have reported the finding of their investigation in the August issue of the journal Emerging Infectious Diseases.

The outbreak involved Klebsiella oxytoca, a bacterium that normally lives in the human gut. It typically causes urinary tract infections, but can also trigger bacteremia — infection in the blood.

It's not uncommon. But when infection control staff at Mount Sinai noticed in the fall of 2006 that they had three or four cases caused by a similar strain, they set out to figure out what the source was in a bid to shut down what appeared to be in-hospital transmission.

Dr. Allison McGeer, Mount Sinai's head of infection control and senior author of the study, says hospitals know that as a rule these bacteria spread from a patient who is carrying them to other patients. Find the colonized patient — a person carrying Klebsiella oxytoca but not sickened by them — and make sure he or she is treated in isolation, and you can prevent transmission.

Using anal swabs, the hospital staff did locate people carrying the bacteria. But despite taking the appropriate measures, the bug continued to spread.

When ICU patients became infected even though there were no Klebsiella oxytoca carriers in the ICU, it became clear there had to be a non-human source. Then began a process of elimination.

Pseudomonas are commonly found in drains. And the sinks in the transplant unit had shallow basins and high, gooseneck spouts that flowed directly into the drain below. Because of that design, the pressure from the spout splashed water out of the drain, spraying nearby surfaces with bacteria-laced droplets.

Dr. Michael Gardam is McGeer's counterpart at the University Health Network. He says since his hospital's outbreak, he believes getting staff to clean their hands with alcohol gel instead of soap and water is the better way to go in many settings.

As reported by The Chronicle Herald.