Investigation of an outbreak of Ralstonia pickettii in a paediatric hospital by RAPD

In 1995, over a 5-day period, Ralstonia pickettii was isolated from six separate blood cultures from sis paediatric patients in four different units of the Bordeaux paediatric hospital. The patients did not present fever or any other symptom of septicaemia. Epidemiological investigation cast suspicion on distilled water and 0.05% aqueous solutions of chlorhexidine used for topical disinfection as the source of R. pickettii. The organism was isolated from three of the seven distilled water specimens and from seven of the thirty-seven chlorhexidine specimens collected. Conventional biochemical tests showed no differences between isolates and antimicrobial agent susceptibility testing indicated that the six blood cultures contained the same strain of R. pickettii. This was confirmed by RAPD (random amplified polymorphic DNA) analysis. The primers P3 (5'AGACGTCCAC3') and P15 (5'AATGGCGCAG3') from the kit 'OPH Operon' (Bioprobe Systems, Montreuil, France) were used. The chlorhexidine solutions and the distilled water used to prepare the solutions were contaminated with various strains of R. pickettii including the patient strain. The distilled water originating from the local pharmacy had been deionized on an ion-exchange resin. Circumstantial evidence points to this water treatment as the source of contamination. RAPD proved to be a discriminatory and reproducible technique in this context, but antibiotyping was also very helpful in detecting outbreak and was equally discriminatory. (C) 2000 The Hospital Infection Society.