RAPID IDENTIFICATION OF MYCOBACTERIUM-XENOPI FROM BACTERIAL COLONIES OR BACTEC CULTURE BY THE POLYMERASE CHAIN-REACTION AND A LUMINESCENT SANDWICH HYBRIDIZATION ASSAY

Oligonucleotide primers were used in the polymerase chain reaction (PC R) to amplify a specific 584-bp DNA fragment, located in the 16S RNA g ene of Mycobacterium xenopi. This set of primers, X222 and X224, was a ble to discriminate between the pathogen and other mycobacterial speci es as well as non-mycobacterial strains; it detected down to 3 fg of M . xenopi DNA, i.e. about one genome equivalent. These oligonucleotide primers proved suitable for the routine identification of M. xenopi cu ltures, starting from one single colony on solid medium or from a liqu id culture in Middelbrook 12B ''Bactec'' medium. In addition, a lumine scent hybridization assay was designed for use on PCR-amplified DNA. T his system, which, for capture, relied on a matrix-bound oligonucleoti de (M30) specific for the genus Mycobacterium and, for detection, on a biotinylated xenopi-specific X221 probe, proved fully specific, highl y sensitive and rapid for the evaluation of M. xenopi Bactec cultures at low growth index.