PSEUDOMONAS-AERUGINOSA AND ENTEROBACTERIACEAE BACTEREMIA AFTER BILIARY ENDOSCOPY - AN OUTBREAK INVESTIGATION USING DNA MACRORESTRICTION ANALYSIS

PURPOSE: An outbreak of gram-negative bacteremia in patients undergoin g endoscopic retrograde cholangiopancreatography (ERCP) was investigat ed to determine the sources of infection and to control transmission. PATIENTS, METHODs, AND RESULTS: The incidence of post-ERCP bacteremia increased from 1.6% (60 of 3,696) procedures to 3.6% (53 of 1,454) pro cedures (relative risk 2.3, p <0.0001) after endoscopes were processed in a new automated disinfector. Bacteremia involved nine species of P seudomonas and Enterobacteriaceae, which were also isolated from proce ssed endoscopes. Seven epidemic strains with highly related genomic ma crorestriction profiles each infected 2 or more patients, accounting f or 29 (55%) episodes of post-ERCP bacteremia. Strains recovered from e ndoscopes and from the disinfector were associated with 22 (42%) and 5 (9%) bacteremic episodes respectively. Effective endoscope disinfecti on was achieved by cleansing and disinfection of a blind channel not p rocessed in the disinfector, additional isopropanol-air flush of all c hannels, and auto-disinfection of the disinfector. In the following pe riod, the incidence of post-ERCP bacteremia returned to the pre-epidem ic rate (1.7%, p = 0.0001). CONCLUSION: Bacterial genome fingerprintin g by macrorestriction analysis enabled delineation of a multi-strain o utbreak of post-ERCP bacteremia. Cross-contamination, and to a lesser extent, common-source contamination, appeared related to inadequate di sinfection of endoscopes processed in an automated disinfector.