Current status of multidrug resistant tuberculosis in a tertiary care hospital of East Delhi.

BACKGROUND AND OBJECTIVE

Multidrug resistant tuberculosis (MDR-TB) is caused by infection due to Mycobacterium tuberculosis which is resistant to both isoniazid (INH) and rifampicin (RIF). It is caused by selection of resistant mutant strains due to inadequate treatment and poor compliance. MDR-TB is a major public health problem as the treatment is complicated, cure rates are well below those for drug susceptible tuberculosis and patient remains infectious for months despite receiving the best available therapy. The drug susceptibility pattern of M. tuberculosis is essential for proper control of MDR-TB in every health care setting, hence the study was initiated with the aim of studying the prevalence of MDR-TB in patients attending a tertiary care hospital in east Delhi.

MATERIALS AND METHODS

Five hundred and forty-three pulmonary and extrapulmonary samples from suspected cases of tuberculosis received in the mycobacteriology laboratory from November 2009 through October 2010 were investigated for M. tuberculosis. All the samples were subjected to direct microscopic examination for demonstration of acid fast bacilli followed by culture on Lowenstein-Jensen (LJ) medium to isolate M. tuberculosis. Identification was done by conventional biochemical methods. Drug susceptibility of isolated M. tuberculosis strains was done by conventional 1% proportion method followed by sequencing of RIF resistant isolates to detect mutations to confirm resistance.

RESULTS AND CONCLUSIONS

M. tuberculosis was isolated from 75 out of 543 suspected cases of pulmonary/extrapulmonary TB. Three of the total 75 M. tuberculosis isolates (4%) showed resistance to any one of the first line drugs. Prevalence of MDR-TB was 1.3%. The sequencing of single MDR strain showed mutations at codons 516, 517, and 518. Amplification of rpoB and sequential analysis of the amplicon is a better way of detection of mutation and the evidence of new mutation in this study indicate that mutations continue to arise, probably due to the ability of M. tuberculosis to adapt to drug exposure.