PSEUDO-OUTBREAK OF MULTIRESISTANT PSEUDOMONAS-AERUGINOSA IN A HEMATOLOGY UNIT

OBJECTIVE: To describe the investigation of a pseudo-outbreak multires istant Pseudomonas aeruginosa fecal colonization in a hematology unit. DESIGN: Retrospective chart review; prospective environmental samplin g and observation of stool culture technique; genotyping by random arb itrary primer polymorphic DNA polymerase chain reaction (RAPD-PCR). SE TTING: An academic tertiary-care hospital. PATIENTS: Between August an d October 1994, P aeruginosa resistant to imipenem, ceftazidime, cipro floxacin, and all aminoglycosides was isolated from surveillance stool cultures from 10 neutropenic patients cared for in the hematology uni t. P aeruginosa, with an identical susceptibility pattern, was isolate d from three patients admitted to the same unit in the year before the ''outbreak.'' Two months before the outbreak, 12 healthcare workers h ad been added to the staff RESULTS: Observation of stool sampling tech niques as performed by healthcare workers revealed that samples for su rveillance cultures were taken from feces in the toilet. When the prop er sampling technique was used, P aeruginosa was not isolated from sto ol samples from 8 of 10 patients with previously positive cultures. P aeruginosa also was isolated from two wash basins, toilet flushing wat er, and a toilet brush. Genotyping by RAPD-PCR showed that the isolate from the toilet flushing water was identical to the P aeruginosa stra ins of eight patients from the outbreak. CONCLUSIONS: This pseudo-outb reak emphasizes the importance of proper sampling techniques and that periodic observation may be necessary to verify proper sampling techni ques.