Analysis of strains of Burkholderia (Pseudomonas) cepacia isolated in a nosocomial outbreak by biochemical and genomic typing.

We analyzed strains of Burkholderia (formerly Pseudomonas) cepacia isolated in a nosocomial outbreak by biochemical and genomic typing methods. One hundred isolates of B. cepacia were obtained from patients at several wards in a single hospital from March 1983 to February 1984. These isolates were classified into 12 groups by a new biochemical typing scheme on the basis of the production of six enzymes and the production of hemolytic substance and yellow pigment. Among them, 33 strains collected from the 12 groups were further characterized by DNA fingerprinting by pulse-field gel electrophoresis, ribotyping, and plasmid profile analysis. Forty-seven strains of B. cepacia of independent origins and 25 isolates from the same hospital obtained 10 years later for a follow-up study were also subjected to analysis. Both DNA fingerprinting and ribotyping clearly discriminated the isolates from different hospitals. Of interest, although the biochemical typing and plasmid profiles of the isolates obtained during 1983 to 1984 in a single hospital were variable, genomic typing identified the majority of the isolates (32 of 33 [97%]) as derivatives of a single strain. Furthermore, a follow-up study suggested the persistence of such derivatives among the isolates after a decade. These results clearly indicated that the outbreak of B. cepacia infection in the hospital was nosocomial in origin. Thus, the usefulness of genomic typing for epidemiological studies of B. cepacia infection was further demonstrated. The biochemical typing revealed the marked variability of phenotypes of B. cepacia.