Affiliations: * National Institute of Health; Department of Medical Sciences
Source: Present at the ASM Annual Meeting 2004
Type strains have always been regarded as standards for the bacterial species they represent. They are usually well characterized, and thus are frequently used for comparison between species as well as nomenclature and taxonomy studies. Sponsored by Health Canada, we conducted a three year international double blind study of 300 isolates from bacterial taxa important in biotechnology: Pseudomonas (Ps.), Burkholderia (B.) and closely related genera. Among them were twenty five type cultures obtained from Belgian Coordinated Collection of Microorganisms (BCCM/LMG) and American Type Culture Collection (ATCC). Eight independent laboratories used eighteen different methods for identification; these included traditional phenotypic and biochemical tests, commercial identification kits (API and BIOLOG), Polyacrylamide Gel Electrophoresis (PAGE), Fatty Acid Methyl Ester analysis (FAME), and 16S rRNA sequencing. The accuracy of identification was organism-specific, varying from 83% to less than 10%. Type cultures of Ps. aeruginosa, Stenotrophomonas maltophilia, Ralstonia pickettii and Ps. luteola were correctly identified by more than 80% of the methods/participants. Commercial ID kits performed well for members of the B. cepacia complex. Overall, PAGE gave the best identification for all the type strains, followed by BIOLOG. Traditional characterization methods identified Ps. tolaasii and Ps. corrugata poorly, but PAGE compensated for these species. Most of the time type cultures were better identified than other strains within the same species. It is interesting to note the type strain of B. vesicular was our worst case of misidentification. However, 14 out of the 18 tests used in this study indicated it as Achromobacter xylosoxidans. Thus, further investigation is needed to resolve the status of B. vesicular type strain.