Pseudo-Outbreak ofPseudomonas aeruginosaandSerratia marcescensRelated to Bronchoscopes

Abstract

AbstractObjective:To investigate an apparent outbreak involving simultaneous isolation ofPseudomonas aeruginosaandSerratia marcescensfrom bronchoalveolar lavage (BAL) samples.Design:Retrospective and prospective cohort studies using chart review, environmental sampling, and ribotyping of all available isolates. Cleaning and disinfection procedures for the bronchoscopes were also evaluated.Setting:A 380-bed private hospital in Sao Paulo, Brazil.Patients:Forty-one patients who underwent bronchoscopic procedures between December 1994 and October 1996 and from whomP. aeruginosaandS. marcescenswere concomitantly isolated. Bronchoscopes and related items were microbiologically assessed.Results:P. aeruginosaand S.marcescenswere simultaneously isolated from BAL samples 12.6% of the time (41 of 324) during the epidemic period versus 1.8% of the time (1 of 54) in the pre-epidemic period (P= .035). Ribotyping revealed two strains ofP. aeruginosaand one of S.marcescensthat were isolated from BAL samples of patients with no signs of respiratory tract infection, suggesting a pseudo-outbreak. Evaluation of bronchoscope disinfection revealed that inappropriate methods were being used. Implementation of simple control measures resulted in a significant decrease in simultaneous isolation of these species.Conclusion:Prevention of pseudo-outbreaks requires meticulous use of preventive measures for infection-prone medical procedures.