OBJECTIVE: To determine the cause(s) of an outbreak of gram-negative bacteremia (GNB) in open-heart-surgery (OHS) patients at hospital A. DESIGN: Case-control and cohort studies and an environmental survey. RESULTS: Nine patients developed GNB with Enterobacter cloacae (6), Pseudomonas aerugi;nosa (5), Klebsiella pneumoniae (3), Serratia marcescens (2), or Klebsiella oxytoca (1) following OHS; five of nine patients had polymicrobial bacteremia. When the GNB patients were compared with randomly selected OHS patients, having had the first procedure of the day (8 of 9 versus 12 of 27, P=.02), longer cardiopulmonary bypass (median, 122 versus 83 minutes, P=.01) or cross-clamp times (median, 75 versus 42 minutes, P=.008), intraoperative dopamine infusion (9 of 9 versus 15 of 27, P=.01), or exposure to scrub nurse 6 (6 of 9 versus 4 of 27, P=.001) were identified as risk factors. When stratified by length of the procedure, only being the first procedure of the day and exposure to scrub nurse 6 remained significant. First procedures used pressure-monitoring equipment that was assembled before surgery and left open and uncovered overnight in the operating room, whereas other procedures used pressure-monitoring equipment assembled immediately before the procedure. At night, operating rooms were cleaned by maintenance personnel who used a disinfectant-water solution sprayed through a hose connected to an automatic diluting system. Observation of the use of this hose documented that this solution could have contacted and entered uncovered pressure-monitoring equipment left in the operating room. Water samples from the hose revealed no disinfectant, but grew P aeruginosa. The outbreak was terminated by setting up pressure-monitoring equipment immediately before the procedure and discontinuing use of the hose-disinfectant system. CONCLUSIONS: This outbreak most likely resulted from contamination of uncovered preassembled pressure-monitoring equipment by water from a malfunctioning spray disinfectant device. Pressure-monitoring equipment should be assembled immediately before use and protected from possible environmental contamination (Infect Control Hosp Epidemiol 1996;17:281-285).
