Detection of <i>Mycobacterium tuberculosis</i> complex DNA by the polymerase chain reaction for rapid diagnosis of cutaneous tuberculosis

Abstract

We assessed the polymerase chain reaction (PCR) technique to detect Mycobacterium tuberculosis complex DNA in 48 paraffin-embedded specimens from 32 patients with different variants of cutaneous tuberculosis, and compared the results with those of culture. A 123 bp product of the IS6110 insertion sequence specific of M. tuberculosis complex was amplified and confirmed by digestion with SalI restriction endonuclease. The time required for the procedure was 3 days. Thirty-seven samples (77.1%) were positive for M. tuberculosis complex DNA. No false positive results were obtained in nine negative controls. Of the 20 specimens tested by PCR and culture, the frequency of positivity was 90% for DNA amplification and 65% for culture. In seven cases of lupus vulgaris, the figures were 100% and 57%, respectively. In the 11 specimens culture negative or not microbiologically tested and PCR negative, evidence for tuberculous infection was provided by the correlation of various relative and absolute criteria. These results show that PCR amplification of the IS6110 insertion fragment is a rapid and accurate means for the detection of M. tuberculosis complex DNA in paraffin-embedded skin biopsies from patients with cutaneous tuberculosis, especially in paucibacillary lesions.