Comparison of biotyping, ribotyping, and pulsed-field gel electrophoresis for investigation of a common-source outbreak of Burkholderia pickettii bacteremia

Abstract

Over a 3-month period, six immunocompromised patients developed one or more episodes of Burkholderia pickettii bacteremia and/or catheter infection. Vials of a commercially available, "sterile" saline for injection which had been used for flushing the patients' indwelling intravenous devices were implicated as the common source of the organisms. No further cases were diagnosed once the use of this saline was discontinued. Twenty-six isolates, including 9 outbreak-related strains from case patients and contaminated saline as well as 17 control strains, were tested comparatively by biotyping, ribotyping with EcoRI and HindIII, and pulsed-field gel electrophoresis (PFGE) with SpeI. Macrorestriction analysis revealed nine PFGE groups and was more discriminating than ribotyping (seven ribotypes) and biotyping (two biovars). Among the outbreak-related isolates, one B. pickettii type was found by the three typing methods. Furthermore, PFGE was useful for subdividing ribotypes and for distinguishing isolates involved in the outbreak from all epidemiologically unrelated strains.