Resistance pattern in drug-resistant pulmonary tuberculosisC Nagaraja, BL Shashibhushan, C Sagar, M Asif, PH Manjunath
Department of Pulmonary Medicine, Rajiv Gandhi Institute of Chest Diseases, BMCRI, Bangalore, Karnataka, India
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0022-3859.85197
Source of Support: None, Conflict of Interest: None
Background : Drug-resistant tuberculosis is an important issue for public health. There is a rise in the trend of drug-resistant tuberculosis, especially multi drug resistance (MDR), in different parts of world, India being one of the high burden countries. This study is undertaken to assess the various patterns of resistance among confirmed drug resistant pulmonary tubercular patients and to initiate second line anti tubercular treatment. Aims and Objectives : To assess various resistance patterns among confirmed drug resistant pulmonary tubercular patients and for the initiation of appropriate drug regimens in our setup. Study Design : An observational prospective study. Materials and Methods : This study was conducted at Rajiv Gandhi Institute of Chest Diseases, Bangalore between January 2005 and November 2010. A total of 309 drug resistant tuberculosis cases were studied. Sputum culture and drug sensitivity were carried out at National Tuberculosis Institute. Drug sensitivity testing done for all first line drugs, except pyrazinamide, by using LJ media. Results : In this study, out of 309 patients, MDR pattern was observed in 224 (72%), of which 20 (6.47%) had resistance only to isoniazid (INH) and rifampicin (RMP), 58 (18.7%) had resistance to INH, RMP, and either of the other first line drugs streptomycinor ethambutol and 146 (47.25%) had resistance to all first line drugs. Poly drug resistance pattern was observed in 72 (23.3%) and Mono drug resistance in 13 (4.2%). Conclusion : In the present study the most common pattern observed is MDR with predominant resistance to INH. There is a rise in the number of drug resistant tuberculosis cases, especially MDR. Hence close monitoring of drug resistant pattern is required to formulate designs of different regimens in the treatment of drug resistant tuberculosis; especially MDR-TB based on accredited laboratory reports, in a specialized center which is very much essential for the betterment of the patients and the community.
Keywords: Drug resistant, resistance, tuberculosis
Tuberculosis (TB) is a major cause of morbidity and mortality in India and accounts for 1/5 th of the world population.  According to World Health Organization (WHO), each year an estimated 9.4 million new cases of TB are detected leading to nearly 2 million deaths, and almost one third of world population is infected by Mycobacterium tuberculosis. In India, the numbers of TB patients are 1.96 million per year and among them 0.8 million are new smear positive cases comprising of 75 new sputum positive cases per lakh annually with 0.33 million deaths per year, i.e., 1000 deaths per day (two deaths every 3 min).  About 40% of all Indians are infected.  Patients infected with HIV are at a greater risk of developing drug resistant TB, more so for Multi Drug Resistant (MDR)-TB. MDR TB levels are less than 3% in new cases and 12% among retreatment cases as per the recent studies.  In India drug resistant pattern vary widely across different parts of the country. The data on drug resistance have been variously estimated by different investigators. Since second line antitubercular treatments (ATTs) are more toxic and less efficacious than first line drugs, the treatment of drug-resistant TB especially MDR TB is more challenging. Hence, this study is undertaken to assess the various patterns of resistance among confirmed drug resistant pulmonary tubercular patients and to initiate second line antitubercular treatment accordingly in our hospital- a tertiary care referral center.
The study was conducted in 309 confirmed drug-resistant TB cases attending as inpatients, in the department of pulmonary medicine, at Rajiv Gandhi Institute of Chest diseases, Bangalore, between January 2005 and November 2010. All sputum AFB positive CAT II failures of age more than 15 years with confirmed reports of drug-resistant pulmonary tuberculosis, from National Tuberculosis Institute (NTI) only, were included in the study. AFB culture and sensitivity reports from other non accredited laboratories were not considered. Sputum culture and drug sensitivity were carried out at NTI, Bangalore, a Revised National Tuberculosis Control Programme (RNTCP) accredited laboratory. Drug sensitivity testing (DST) was done for all first line drugs, except pyrazinamide (PZA), by using LJ media. Sputum isolate from sputum smear positive patients of pulmonary tuberculosis were processed by modified Petroff's method  and cultures of all samples were done on LJ Media and incubated at 37 o C, examined weekly up to a period of 6-8 weeks. Cultures with no growth were declared negative at the end of 8 weeks. Any growth on LJ Media was confirmed by AFB smear and biochemical tests were done wherever necessary to differentiate the species of mycobacterium. In vitro DST was carried out by proportion method and the results were read. The first reading is taken after 28 days of incubation and if the isolate is susceptible a second reading is taken on 42 nd day. Colonies are counted only on the slopes seeded with the inoculums that have produced exact readable counts or actual counts (up to 100 colonies on the slope). Ratio of the number of colonies in drug containing slopes by that in drug free slopes gives the percentage resistance (R). If R>1%, the isolate is taken as resistant. , H37Rv strain is used as standard control.
Total of 309 patients with confirmed reports of drug resistant TB from NTI, Bangalore were analyzed during the study period. None of the patients were tested for PZA sensitivity. The associated comorbid conditions seen in some of these 309 patients were diabetes mellitus (DM) in 26 patients, Hypertension in four patients, IHD with DM in two patients, Cor pulmonale in two patients, HIV in six, Hansen's disease in one and hemophilia in one patient.
Of these 309 patients, 202 patients had cavitary lesions while the remaining 107 had only infiltrates. 244 patients had bilateral lesions, 35 had right-sided lesions and the remaining 30 had left-sided lesions.
224 (72.4%) patients had MDR pattern of which 146 (47.25%) patients were resistant to all first line drugs, 58 (18.7%) were resistant to INH, RMP with one of the either first line drugs and 20 (6.47%) patients had resistance only to INH and RMP.
Poly drug-resistant pattern was seen in 72 (23.3%) patients and the remaining 13 (4.2%) of patients had mono drug-resistant pattern [Table 1].
Tuberculosis remains one of the deadliest diseases in the world. Drug-resistant tuberculosis is a significant threat to tuberculosis epidemic control because only a few effective drugs are available against Mycobacterium tuberculosis. The prevalence of MDR-TB increases tenfold after unsuccessful treatment of new tuberculosis cases.  Thus, the highest priority in fighting drug resistant TB especially MDR-tuberculosis is its prevention by appropriate treatment. In regions with a high prevalence, the realization of a drug resistance test is very important for correct management and for monitoring levels of resistance. The emergence of M. tuberculosis strains that are resistant to antimycobacterial agents, although not a new problem, has recently received increased attention due to the dramatic outbreaks of MDR in HIV-infected patients. 
In the present study, among total of 309 patients, MDR pattern was observed in 224 (72.4%) patients of which 20 (6.47%) patients had resistance only to INH and RMP, 58 (18.7%) patients had resistant to INH and RMP with either of the other first line drugs, and 146 (47.25%) patients had resistant to all first line drugs. In Sharma et al. study, MDR pattern was observed in 40 (20.4%) isolates out of a total 196 isolates, of which 36 isolates were resistant to RMP and INH whereas 4 isolates were resistant to RMP, INH, and streptomycin (SM).  Poly drug resistant pattern was observed in 72 (23.3%) patients and Mono drug resistance in 13 (4.2%) patients, MDR TB being the predominant observed drug-resistant pattern. Tatar et al., showed 38.7% as MDR TB, 22.9% as poly drug resistance and 37.8% as mono drug resistance with MDR TB being the predominant resistance pattern. An increased trend of MDR pattern was observed in our study.
In the present study, 47.24% are resistant to INH + RMP + SM + ethambutol (EMB), 12.62% to INH + RMP + SM, 6.14% to INH + RMP + EMB, and 6.47% to INH + RMP. Tatar et al., study showed various multidrug resistant patterns as 18.2% for INH + RMP + SM + EMB, 8.5% for INH + RMP + SM, 6% for INH + RMP + EMB, and 6% for INH + RMP. Resistance to all four first line drugs being the predominant multi drug-resistance pattern in both the studies.
The pattern of poly drug resistance observed in the present study were 11.32% for INH + SM + EMB, 6.14% for INH + SM, 2.26% for INH + EMB, 1.16% for SM + EMB, 0.64% for RMP + SM + EMB, 0.64% for RMP + EMB, and 0.64% RMP + SM. Tatar et al., study showed as, 7.3% for INH + SM, 6% for SM + EMB, 4.8% for RMP + SM, 3.6% for INH + EMB, and 1.2% for RMP + EMB.
Individual mono drug resistance pattern observed in the present study was 2.57% for INH, 0.64% for RMP, 0.64% for SM, and 0.32% for EMB with predominant resistance for INH.
Tatar et al., study showed individual mono drug resistant pattern as 14.6% for SM, 9.7% for EMB, 7.3% for RMP and 6%for INH with a predominant resistance to SM. Shah = et al., study showed this pattern as 7.5% to INH, 1.4% to SM, 0.97% to RMP and 0.4% to EMB with predominant resistance for INH. Chand et al., showed individual mono drug resistance as 26.56% to SM, 15.10% to RMP, 7.29% for INH, 2.08% for PZA, and 0.52% for EMB with a predominant resistance to SM.
As far as isolated resistance pattern for individual drug in all the isolates (309) is concerned, the pattern observed in this study was 93.5% to INH, 82.2% to SM, 76.05% to RMP, 70.87% to EMB with predominant INH resistance [Table 2]. Dheodhar et al. study  showed 58.55% resistance to RMP, 46.95% to SM, 30.41% to INH and 3.67% to EMB with predominant RMP resistance.
In this study the resistance reported to the individual drugs is very high because of increased number of MDR isolates. Increased MDR isolates may be a point of controversy and requires further studies to know the reasons for increased number of MDR cases among drug-resistant TB in India.
As there is a rise in trend of drug resistant TB with few treatment options available there is a concern over the treatment options for the future generation, hence, it requires early detection of Drug resistant TB and its treatment with appropriate regimen based on drug resistant pattern from RNTCP accredited laboratory. It is essential at this stage to combat tuberculosis and make the community free from drug resistant TB, if not eradicating, and to bring tuberculosis under control.
About 1/3 rd of population is infected with Mycobacterium tuberculosis and there is a trend of steady increase in patients with drug-resistant TB. Much attention has to be given for early diagnosis and management by formulating a proper regimen as per resistance patterns based on sputum culture sensitivity pattern from an RNTCP accredited laboratory for better treatment outcome and to prevent further spread of the disease. This study has been taken to analyze the various resistance patterns in drug resistant TB patients and to initiate a proper regimen accordingly for betterment of patient and the community. The most common drug-resistant pattern observed is MDR TB and INH resistance is the most common observation seen in this study. Accurate diagnosis with proper supply of drugs as per resistance pattern, under supervision, is the key to success in treating a case of drug resistant TB. Irrational use of second line drugs with inappropriate individualized regimens, based on nonaccredited laboratory reports, and use of empirical line of treatment in drug resistant TB, not according to guidelines, in an unspecialized set up, should be discouraged and condemned.
[Table 1], [Table 2]