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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. Burkholderia pickettii is a nonfermentative gram-negative rod isolated from environmental sources and infrequently from clinical samples (5). It is an occasional agent associated with pseudobacteremias or asymptomatic colonization of patients (8, 13, 19). However, this bacterium has been identified in a few reports as the etiologic agent of true bacteremias (2, 4, 7, 8, 12, 14, 15). Most of the bloodstream infections were traced to the contamination of parenteral fluids or of medical equipment (14). We report here on an outbreak of B. pickettii bacteremias at a 650-bed teaching hospital in Liege, Belgium. From June to August 1994, six immunocompromised patients developed B. pickettii bacteremia and/or catheter infection. All had permanent central venous catheters. The patency of these lines was maintained by regular flushing with heparin solution. The organism was isolated from multiple vials containing commercially available, "sterile" saline without preservative (Physio-Sterop; Sterop, Brussels, Belgium) used for dilution of heparin. Randomly selected isolates originating from both clinical cultures and contaminated vials, as well as control strains, were characterized by biotyping, ribotyping, and DNA typing by pulsed-field gel electrophoresis (PFGE).

Ribotyping carried out with a nonradioactive probe (acetylaminofluorene ribosomal RNA kit I from Eurogentec, Seraing, Belgium) was performed for the characterization of 139 hospital strains of Serratia marcescens. These strains, which belonged to 11 biotypes and 1 nontypeable group, were isolated in seven hospitals in Belgium between 1986 and 1992. EcoRI and HindIII were used to obtain cleavage patterns. Analysis of the results produced 27 different patterns with EcoRI and 23 patterns with HindIII. Typeability reached 100%. Combination of the patterns obtained with each enzyme produced 38 distinct ribotypes. Percent similarity values, calculated by using the Dice coefficient and unweighted-pair group average linkage clustering, showed four main clusters and nine subclusters of ribopatterns at a similarity rate of approximately 80% or less. These groups did not coincide with those delimited by biotyping, although a rather good correlation was observed. The simultaneous use of the two methods has potential value in epidemiological studies. and ESN, five other hospitals in the Liège area; BXL, Hôpital Universitaire Brugmann, Brussels, Belgium. b ?, month unknown. c RFLP, restriction fragment length morphism.2638 CHETOUI ET AL. J. CLIN. MICROBIOL.

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