DIAGNOSIS OF CUTANEOUS TUBERCULOSIS IN BIOPSY SPECIMENS BY PCR AND SOUTHERN BLOTTING

Aims-To evaluate the use of a gene amplification and hybridisation met hod for detecting mycobacterial nucleic acid as a possible diagnostic method for cutaneous tuberculosis infection. Methods-Biopsy specimens from 20 patients with various skin conditions of possible tuberculous aetiology were studied. Six patients had ulcerative nodules, seven lup iform lesions, two non-necrotic granulomas, one scrofulous lichen, one impetigo, one erythematosus lesions, one warty lesions, and one suspe cted tuberculous lipoma. Biopsy specimens were stained using Ziehl-Nee lsen stain and cultured in Lowenstein-Jensen medium. DNA was extracted and then amplified by PCR using primers specific for the Mycobacteriu m tuberculosis complex. Specificity was confirmed by Southern blotting . Results-Of the specimens, 30% were positive for mycobacteria on stai ning with Ziehl-Neelsen stain, 60% were culture positive and 85% PCR p ositive. Only 35.2% of specimens were positive with all three techniqu es. A further 32.5% were both culture and PCR positive. All PCR negati ve samples were also negative when cultured or stained with Ziehl-Neel sen stain. Of the PCR positive specimens, 29.4% were negative when cul tured or stained. Conclusions-PCR, using suitable primers, is an effic ient and sensitive method for the diagnosis of cutaneous tuberculosis.