An outbreak of Pseudomonas aeruginosa (PA) in the Neonatal Intensive Care Unit (NICU) was found to be due to improper modifications of the hospital water system serving the NICU. Molecular epidemiology confirmed a point source outbreak and helped locate the origin. Bringing the water system to code ended the outbreak.

Pseudomonas aeruginosa is an occasional pathogen in the NICU, with less than one isolate noted monthly over the past 2 years. However, when 8 isolates were noted in a single month, infection control investigated. As construction of a new NICU had recently begun directly behind the current NICU, the site was investigated. Site engineers denied common utilities(water, air, gases, etc). As PA is often water and device related, ventilators and associated medical devices were extensively cultured (>100 sites). All cultures were negative. However, pulsed field gel electrophoresis (PFGE) disclosed that 12 of 14 involved infants had identical strains of PA. On site inspection disclosed a water line transversing the construction site and subsequently serving 2 sinks in the nursery (including one of the two scrub sinks). The water lines in the construction site had numerous branches that had been capped off with up to 10 feet of dead space. Water passing these dead spaces then served the NICU. Culture of the water from the involved sinks yielded strains of PA similar to patient isolates by PFGE.

Patient isolates included blood (1), IV catheter (1), CSF (1), and ET aspirate (13). There was more than 1 isolate per patient. Patients with PA were cohorted by location and nursing. Handwashing and isolation were re-emphasized. The dead spaces were corrected (capped to the minimum length of about 6-12 inches). The involved sinks were removed from use until correction and chlorine decontamination were completed. All subsequent isolates of PA have been dissimilar strains (less than one per month) in more than 12 months of follow up. Construction can affect patients in “distant” sites, underlining the need for review of construction projects by infection control. PFGE helps identify outbreaks, assists in confirmation of the source, and contributes to eventual control. Early detection of a point source outbreak and correction of the cause limited morbidity and mortality.