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A commercially available DNA probe (the AccuProbe Mycobacterium kansasii culture identification test, Gen-Probe, USA) for the identification of Mycobacterium kansasii was tested on a panel of 143 fully characterized mycobacterial strains. The isolates included 70 Mycobacterium kansasii and 73 mycobacteria other than kansasii. The specificity was 100% while the sensitivity was 72.8%. This sensitivity is unusually low in comparison with that of commercial DNA probes for other mycobacteria and confirms a previous study that found genetic heterogeneity within the species Mycobacterium kansasii. Strains that do not hybridize with the AccuProbe are particularly prevalent in Italy and perhaps elsewhere in Europe.

A new biphasic system (MB Check, Roche) for isolation of mycobacteria from clinical specimens was evaluated by eight different microbiological laboratories in comparison with methods routinely used in the respective laboratories. Altogether 1125 clinical specimens were processed; pretreatment, if performed, was by a variety of methods. Mycobacteria were recovered from 167 specimens with the biphasic system and 165 specimens with the other methods. The average time required for isolation of Mycobacterium tuberculosis was 22.6 days with the biphasic system and 24.7 days with egg-based media; for other mycobacterial species it was 23.5 versus 20.8 days. The inclusion of a chocolate agar section in the biphasic system facilitated the early detection of contaminants, while the NAP-containing section appeared unable to differentiate Mycobacterium tuberculosis from other mycobacterial species. The biphasic system, which enables recovery of mycobacteria in small laboratories without specialized equipment, is more practical than conventional methods and at least as sensitive.