Sinks installed in hospital rooms to prevent infections actually turned out to be the source of a superbug infection in a Toronto hospital that killed 12 people, a journal article says.

The deaths occurred in the surgical intensive care unit of Toronto General Hospital between December 2004 and March 2006. A total of 36 patients either became sick or carried the bacteria without illness.

The ICU had recently been renovated when patients started getting sick with a multi-drug-resistant strain of Pseudomonas aeruginosa, but doctors couldn't figure out how it was being spread. The bacteria thrive in drains, where they form sludges called biofilms.

"The big design flaw with the sink was that the gooseneck where the water is coming out was positioned directly over the drain itself," said Dr. Michael Gardam, senior author of the article, published in the January issue of the journal Infection Control and Hospital Epidemiology.

"So when you washed your hands, that water wasn't hitting the side of the bowl first, it was hitting the drain directly, splashing inside the drain, and then causing those drain contents to splash out."

It took a painstaking investigation, which involved testing all the sinks many times, before the researchers discovered that water splashed bacteria up to countertops where nurses stored gloves and prepared dressings.

When investigators used ultraviolet light in a darkened room, they found signs that the splatters travelled at least one metre.

Based on the evidence, hospital staff decided to remove the sinks. No further cases were reported.

Splash guards were then installed to stop water from getting on work surfaces.

Gardam said he and his colleagues published the report to get the word out that sinks can spread infection in hospitals, where people with weakened immune systems may fall ill from Pseudomonas.

The report shows the importance of placing sinks close to beds or treatment areas, but not too close, said Dr. Andrew Simor, an infection control expert at Toronto's Sunnybrook Health Sciences Centre.

With files from the Canadian Press