Pulsed field gel electrophoresis and random amplified polymorphic DNA molecular characterization of Ralstonia pickettii isolates from patients with nosocomial central venous catheter related bacteremia

Over a period of 18 months 3 clusters of central venous catheter-related Ralstonia pickettii bacteremia occurred in 3 different units of the same hospital. In order to investigate the relatedness of the clinical isolates we studied 15 strains using pulsed-field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA (RAPD) techniques. The combined analysis of the results obtained by these two methods led us to conclude that all the patients except one were infected by a single clone comprising two variants circulating in the units. Only one case was due to a different strain, probably originating outside the ward. PFGE and RAPD appear to be discriminatory techniques to study the clonal relationship among the isolates and can represent a good tool to perform the epidemiological investigation of an outbreak.