Ten years after an outbreak was resolved in a pediatric university hospital, Pseudomonas aeruginosa was still detected on various sink components by quantitative PCR, leaving the potential for the bacterium to recover its culturability under favorable conditions, according to Canadian researchers.
“In a hospital environment, this finding suggests that failure to maintain good practices, or presence of disrupting events such as renovation, may act as promoting factors leading to increased concentrations and risk of patient exposure,” Emilie Bédard, PhD, of the department of civil engineering at Polytechnique Montréal, and colleagues wrote in their study.
In 2004 and 2005, a P. aeruginosa outbreak occurred in the pediatric neonatal intensive and intermediate care units at the Centre Hospitalier Universitaire Sainte-Justine, a 450-bed pediatric hospital in Montreal. The outbreak sickened 27 patients, six of whom died.
An investigation of the outbreak determined that sink drains and aerators were the infection source.
Bédard and colleagues performed a post-outbreak prospective study, taking samples from the water, aerator and drain of sinks in the units, which they analyzed by culture and quantitative PCR (qPCR). They detected P. aeruginosa in 21% of the sinks they sampled. They also found that qPCR demonstrated greater sensitivity, yielding a 50% positive sample rate compared with 7% for culture.
In addition, the researchers found that copper concentrations in the water affected culturability but not viability, suggesting that culturability could be revived once the copper stress is decreased.
Environmental factors, particularly the faucet-drain configuration, seemed to influence positive results. Bédard and colleagues found higher positive results when the faucet was aligned behind the drain. Proper sink design and efficient drainage maintenance could reduce the rates of retrograde P. aeruginosa contamination, they said. Research on the optimal faucet-drain design however, is necessary.
“These results demonstrate the importance of defining a clear and detailed protocol to determine the design of and the precise maintenance required for water systems, including drains,” the researchers wrote. “Furthermore, detection by qPCR is a valuable tool for rapidly identifying positive sites in an outbreak investigation and in direct sampling and typing efforts.” – by Colleen Owens
Disclosure: The researchers report no relevant financial disclosures.