PCR in the diagnosis of cutaneous tuberculosis

RESUMO

Seeking to improve the laboratory diagnosis of Cutaneous Tuberculosis, a study was carried out on the application of PCR technique in macerated, decontaminated(with 4 percent H2SO4 for elimination of normal microbiot), neutralized (with 4 percent NaOH)biopsies tissues samples stored at -20liC. Of the 37 samples submitted for study, 16.22 percent were positive by microscopy for acid-fast bacilli (concentrated method) and in 43.24 percent the Mycobacterium tuberculosis was isolated in L que wenstein-Jensen medium. Using a M. tuberculosis complex specific primer set (gene sequence for 16S rDNA), the mycobacterial DNA was detected in 24.32 percent of the biopsies. The sensitivity and specificity of PCR were 43.7 percent and 90.4 percent, respectively. Due to low sensitivity and discrepant results between bacteriological techniques and PCR methodology, the samples were repeated in a new PCR with primers for the IS6110 target. The sensitivity and specificity of PCR for the IS6110 target obtained 100 percent in comparison with the culture method. The results confirm the effectiveness of PCR methodology using primers for the IS6110 gene sequence and permit the PCR method to be applied to frozen cutaneous biopsies sent by services that do not identify the M. tuberculosis by the biology molecular method.