Detection of Multi-Drug-Resistance in Extra Pulmonary Tuberculosis by Indirect GenoType MTBDRplus Line Probe Assay

Abstract

Introduction: Approximately 15 to 20 percent of tuberculosis patients have extra-pulmonary tuberculosis (EP-TB), which is often difficult to diagnose. Further multi drug resistant tuberculosis (MDR-TB) in EP samples has not been reported. The aim of the present study was rapid diagnosis of MDR-TB in EP samples by using Mycobacteria Growth Indicator Tube (MGIT) 960 and GenoType MTBDRplus Line Probe Assay (LPA). Methods: A total of 429 extra pulmonary specimens (pleural fluid, lymph node biopsy, cerebrospinal fluid, skin biopsy, urine, faeces) were processed for acid fast bacilli (AFB) smear microscopy and culture by MGIT-960. SD Bioline TB Ag MPT 64 rapid assay was carried out on MGIT positive isolates to differentiate between MTB and Non Tuberculous Mycobacteria (NTM). Growth obtained was tested by Line Probe assay (LPA)- GenoType MTBDRplus assay for the identification of Rifampicin and Isoniazid resistance and GenoType CM-AS assay for species identification of NTM. Results: Among 429 specimens, 58 (13.5%) were AFB positive and 371 (86.5%) were negative on MGIT 960 culture. Amongst 58 positive isolates, 56 were MTB (96.6%) and 2 (3.4%) were NTM, subsequently identified as M. fortuitum and M. intracellulare. In 56 MTB positive isolates, 35 (62.5%) were sensitive to Rifampicin (RFM) and isoniazid (INH). Two isolates (3.6%) were found mono RFM resistant, 11 (19.6%) were mono INH resistant and 8 (14.3%) were resistant to both (MDR). Conclusion: Mycobateria were isolated in 13.5% cases, 14.3% of these were found to be MDR-TB. Overall MDR in EP-TB may be in the same range as pulmonary TB as there was no isolate in 371/429 specimens/cases, this may be due to impact of prior therapy. All these issues need to be investigated by more sensitive molecular methods and correlated microbiologically as well as clinically. Specimens from EP-TB cases must be processed for LPA and DST which will be of help in rapid diagnosis of MDR-TB and institution of right treatment strategy.

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