Gram-Negative Bacteremia in Open-Heart–Surgery Patients Traced to Probable Tap-Water Contamination of Pressure-Monitoring Equipment

Abstract

To determine the cause(s) of an outbreak of gram-negative bacteremia (GNB) in open-heart-surgery (OHS) patients at hospital A. Case-control and cohort studies and an environmental survey. Nine patients developed GNB with Enterobacter cloacae (6), Pseudomonas aeruginosa (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. 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.