RAPID DIAGNOSIS OF GENITOURINARY TUBERCULOSIS BY HYBRIDIZATION POLYMERASE CHAIN REACTION AND NON-RADIOACTIVE DNA

Objective: To establish a polymerase chain reaction (PCR) assay for the rapid detection and identification of mycobacteria in urine, and to assess the value of such assay in routine laboratory diagnosis of genitourinary tuberculosis. Materials and Methods: Urine specimens from 1000 patients with clinical suspicion of urinary tuberculosis were examined. Two assays for the detection and identification of Mycobacterium tuberculosis (M. tuberculosis) complex and mycobacteria other than tuberculosis (MOTT) by non-radioactive DNA hybridization of PCR-product were applied. The first assay used PCR primers and probe derived from M. tuberculosis species-specific DNA insertion sequence, IS6110. The second utilized mycobacterium genus-specific sequence encoding ribosomal ribonucleic acid (16s rRNA). The results obtained by PCR were compared with those obtained by standard microbiological methods, acid-fast bacilli (AFB) stain and culture. Results: Compared with cultures, the sensitivity of AF'B staining was 52.07% and the specificity was 96.7%. In comparison to the results of culture, the overall sensitivity and specificity of the IS6110-PCR assay was 95.59% and 98.12% respectively. While the corresponding results for the 16s rRNA gene-PCR were 87.05% and 98.9%. Conclusion: The high sensitivity and specificity in addition to the potential for rapid detection of mycobacteria, makes this test a useful tool in the clinical management of mycobacterial infection in urine. Urine specimens may contain M. tuberculosis andor other mycobacteria; therefore, there are advantages in using genus-specific primers in parallel with species-specific primers in PCR assay. Tuberculosis remains the largest cause of death in the world from a single infectious disease. The resurgence of tuberculosis and the appearance of multiple drug resistant strains of Mycobacterium tuberculosis (M. tuberculosis) have intensified the need for the use of rapid methods for its detection.' The genitourinary system ranks second to the respiratory system as the most common site of tuberculous infection. Worldwide, the genitourinary form of the disease accounts for 14% of the non-pulmonary manifestation. In the Western world only between 8 to 10% of patients with pulmonary tuberculosis developed renal tuberculosis, compared with an incidence of 15 to 20% in the underdeveloped countries.2 The laboratory diagnosis of genitourinary tuberculosis (TB) is currently based on acid-fast staining and cultures on solid andor liquid media. Staining is a rapid screening test, but its sensitivity is low, especially in specimens obtained from extra-pulmonary site^.^-^ Cultures on solid media are labor-intensive and require up to 8 weeks of incubation to achieve the maximum sensitivity.6 Radiometric liquid culture (BACTEC), which is the most widely utilized rapid culture technique, requires an average of 13 days to become positive. The use of PCR to detect the presence of M. tuberculosis in clinical samples has been widely rep~rted.~-l~ Most of these investigations were limited to materials obtained from the respiratory tract and experience with specimens of non