Detection of 123 bp fragment of insertion element IS6110 Mycobacterium tuberculosis for diagnosis of extrapulmonary tuberculosis.

Purpose: Extrapulmonary tuberculosis (EPTB) is emerging problem in developing and developed countries. The diagnosis of EPTB in its different clinical presentations remains a true challenge. IS6110-based polymerase chain reaction (PCR) is used for rapid identification and positivity rate of the Mycobacterium tuberculosis complex in clinical isolates of different sites of EPTB. The present study was carried out to study the prevalence of M. tuberculosis complex in clinical isolates of EPTB at tertiary care centres in Lucknow.

Materials And Methods: Seven hundred fifty-six specimens were collected from the suspected cases of EPTB which were processed for Mycobacteria by Ziehl Neelson (ZN) staining and BACTEC culture. All the specimens were also processed for IS6110-based PCR amplification with primers targeting 123 bp fragment of insertion element IS6110 of the M. tuberculosis complex.

Results: Of these 756 specimens, 71(9.3%) were positive for acid fast bacilli (AFB) by ZN staining, 227(30.1%) were positive for mycobacteria by BACTEC culture and IS6110 PCR were positive for M. tuberculosis complex in 165 (20.7%) isolates. We found a significant difference in sensitivities of different tests (P<0.05).

Conclusions: This study reveals the positivity of M. tuberculosis complex in clinical isolates of EPTB case in tertiary care hospitals in Northern India. 72.7% of M. tuberculosis complex was confirmed by IS6110-PCR in culture isolates from different sites of EPTB. The high prevalence of the M. tuberculosis complex was seen in lymph node aspirate and synovial fluid. However, utility of PCR may play a potentially significant role in strengthening the diagnosis of EPTB especially targeting IS6110.