Resistance Patterns among Multidrug-Resistant Tuberculosis Patients: A Multi-Center Study from Pakistan

Background: The high burden of multi-drug resistance tuberculosis (MDR TB) is a matter of great concern. The increasing resistance to anti tuberculosis drugs has been the area of growing concern and are posing threats to TB control. The aim of this study was to evaluate the drug resistance patterns for the first line and second line anti-Tuberculosis drugs in multiple drug resistant tuberculosis (MDR-TB) patients. Method: The study was retrospective, observational, employing purposive, non-random sampling technique for data collection conducted at the TB Clinic- of the different healthcare centers in the provinces of Pakistan Sindh and Baluchistan from December 2010 to May 2016. All bacteriologically confirmed TB patients who were found to be Rifampin Resistant (RR) on Genotypic drug susceptibility testing (GXP), or detected to be drug resistant on phenotypic Universal drug susceptibility testing were enrolled into the study. Results: Out of total 3776 patients, 96.3% were resistant to Rifampicin and 94.7% were resistant to Isoniazid. 25.5% isolates were resistant to all five first line drugs. Resistances against Pyrazinamide and Ethambutol was 54.2% and 51.6% respectively. 36.3% patients were resistant to Fluoroquinolones (FQ), 9.7% were resistant to Ethionamide (Eto) and 4.1% were resistant to both FQ and Eto. 33.5% patients were MDR plus resistant to FQ. However, the resistance to both FQ plus Aminogycosides was quite low, 2.7%. Conclusion: The drug resistance rates are quiet high in MDR-TB for both first line and second line drugs. The standardized MDR TB regimen needs to be updated, based on the prevalence of drug resistance patterns in the community for the effective management of drug resistant TB.


Introduction
Drug resistance pattern among MDR-TB patients is of critical importance for its role in designing of individualized regimen and the control of TB 1,2 . Pakistan ranks five among the 22 high burden countries in the world for MDR TB 3,4 .The results of a recent drug resistance surveillance carried out in Pakistan by the National TB Control Program (NTP), estimated MDR TB in All patients diagnosed on GXP and show resistance to rifampicin are put on standardized second line drugs (SLDs) recommended by WHO 5 . All contacts with TB are presumed to have the same DST as the index case and are started on the same regimen, until DST results become available in 4-6 weeks. The regimen may be modified as needed, based on the DST results.
The primary aim of this study was to document the resistance patterns of the MDR TB patients for the first line and second line drugs in Pakistan.

Methodology
The study was retrospective, observational, employing purposive, non-random sampling technique for data collection. All bacteriologically confirmed TB patients who were found to be RR on Genotypic drug susceptibility testing (GXP), or detected to be drug resistant on phenotypic Universal DST from December 2008 to May 2016 were enrolled in the Healthcare Centre's situated in provinces of Sindh and Baluchistan, Data was extracted from Electronic Numerical Recording System (ENRS) that is a uniform format for data storage provided by NTP across all Programmatic management of drug resistant tuberculosis (PMDT) sites. The collected data was then analyzed using Spss version 19.0. Frequency distribution and percentages were calculated using frequencies.

Results
During the study period December 2010 till May 2016, 3776 patients were enrolled on ENRS of all 9 PMDT sites. 1812 (48%) were male, with the mean age 35 years (range 1-85 years).
DST results were available for 2985 (79%) patients and were included in the study, while GXP test was performed for 3144 (83.3%) patients. The results of Universal DST were not always mutually exclusive with GXP results, as discrepancies were often noted: RR might be detected on GXP, but susceptible to Rifampicin on Universal DST; RR might not be detected on GXP but phenotypic result may show RR on DST. Patients detected as RR on GXP, while culture reported negative at baseline were 278 (7.4%) as given in  The overall resistance pattern for the first and second line ATT are shown in Table 1.  While table 2 shows resistance to all first line drugs was seen in 775 (25%) of the cases. Resistance to at least rifampicin and isoniazid was seen in 2760 (93%) of the patients , while the rest were enrolled on MDR regimen as they were RR on GXP, or RR with resistance to drugs other than isoniazid on DST. A significant number of patients, i.e. 1085 (36%) had fluoroquinolone (FQ) resistance. Moreover, resistance to ethionamide (Eto) was also significant among this cohort 291 (10%). Hence, the probability of co resistance with isonaizid in patients found to be RR on Gene Xpert is 93%. Co-resistance of Eto with FQ was 4%. The prevalence of extensive drug resistance (XDR) TB (defined as resistance to isoniazid and rifampicin plus any FQ and at least one second-line anti-TB injectable drug) was 3%. 3111 (83%) of the patients were diagnosed on GXP results and enrolled on standardized regimen till their DST results became available. Another study conducted at Armed forces institute of pathology (AFIP) Rawalpindi, Pakistan reported resistance to the FQ and all first group five drugs 52.7% and 62.6% respectively 3 , which is higher than that found in our study, i.e. 25% and 36%. The same study showed resistance to Eto as 13% while in our cohort it was found to be 9%. The study however had smaller sample size (100 patients) and a single center study 3 .
Another study conducted in Mumbai, India reported resistance to fluoroquinolones as 69.1% 6 , which is much higher than that found in our study. The same study reported resistance with amikacin and capreomycin as 14% and 12%, which is much higher than that found in our study (2% and 1% respectively). Discordance was also found in resistance to Eto (50% versus 9% in this study alarming situation and emphasize special attention to the patients for better treatment outcomes because resistance to anti-TB drugs increases the risks for poor treatment outcomes 9 .

Conclusion
The standardized MDR TB regimen needs to be updated, based on the prevalence of drug resistance patterns in the community for the effective management of drug resistant TB, and to prevent the transmission of infection in the community. Primary and acquired resistance patterns of the population may help to select the regimen for new and retreatment cases.

Conflicts of Interests
None.