**6. Radiological features in patients with MDR/XDR-TB**

A recent study in South Korea showed 100% of lung nodules, 60% of lung consolidation, and 47% of lung cavities that were mainly located in the upper and middle lung zones in XDR-TB patients whereas less frequent lung nodules and ground-glass opacity lesions were found in XDR-TB patients compared to the patients with anti-TB drug-susceptible pulmonary TB [50]. More frequent multiple lung cavities, lung nodules, and bronchial di‐ latation were found in both MDR-TB and XDR-TB patients compared to the patients with anti-TB drug-susceptible pulmonary TB [50]. There was no different radiological findings between MDR-TB and XDR-TB patients [50]. Another recent study in South Ko‐ rea revealed that micronodules and tree-in-bud appearance were found in 100% of the pulmonary XDR-TB patients whereas lung consolidations, lung cavities, bronchiectasis, lobar consolidations were found in 85%, 85%, 80%, and 70%, respectively [51]. This study showed a significantly larger extent of tree-in-bud appearance and lung consolidations compared to the MDR-TB patients [51]. In childhood patients, chest radiological features at the time of diagnosis demonstrates lobar opacification, intrathoracic lymphadenopathy, particular hilar lymph nodes, and airway narrowing [52]. Chest radiological features of three patients with MDR-TB who attended the 10th Zonal Tuberculosis and Chest Disease Centre, Chiang Mai, Thailand are shown in the Figure 4 (A,B,C) which demonstrated a single cavity at the upper lung zone in two patients and no lung cavity in another one. These three patients possibly attended the 10th Zonal Tuberculosis and Chest Disease Centre, Chiang Mai, Thailand at the earlier stages compared to the above study results.

**7. Regimens used in treating patients with drug-resistant tuberculosis**

A recent study on MDR-TB treatment revealed that use of later generation quinolones (moxifloxacin, gatifloxacin, sparfloxacin, levofloxacin), ofloxacin or ethionamide/prothiona‐ mide, use of four or more likely effective drugs in the initial intensive phase, and three or more likely effective drugs in the continuation phase was associated with the treatment success compared to the treatment failure or relapse [53]. The duration of initial phase up to 7.1-8.5 months and the total duration of treatment up to 18.6-21.5 months increased the chances of treatment success [53]. In 2011, the WHO recommended the regimens containing a fluoroqui‐ nolone, pyrazinamide, ethionamide (or prothionamide), para-aminosalicylic acid (or cyclo‐ serine), and a second-line injectable drug with more than 20 months of treatment duration [54]. Five MDR-TB control projects with used DST results and previous treatment history were conducted among 1,047 MDR-TB patients in 5 resource-limited settings with well-established DOTS programmes (Manila, Estonia, Latvia, Lima, and Tomsk) in 1999 for Lima and Manila, 2000 for Tomsk and Latvia, and 2001 for Estonia [55]. At least 4 drug (ethambutol, pyrazina‐ mide, cycloserine, clofazimine, para-aminosalicylic acid, ethionamide, or prothionamide, augmentin, clarithromycin or thiacetazone) including an injectable drug (kanamycin, amika‐ cin, capreomycin, or streptomycin) and a fluoroquinolone (ofloxacin, ciprofloxacin, or levofloxacin) were administered for the duration of treatment (18-24 months) except for the injectable drug, which was administered for a specified interval after the patient' s specimens were culture-negative [55]. Monthly sputum-AFB smear and culture were monitored [55]. Every 6-months (Manila and Lima) and 3-months chest radiographs (Tomsk, Latvia, and Estonia) were performed [55]. The treatment outcomes among new and previously treated MDR-TB patients revealed 74.8% and 68.3% cured patients, 2.5% and 0.3% completed treat‐ ment patients, 4.2% and 7.0% failed treatment patients, 3.4% and 14.2% dead patients, and 77.3% and 66.6% treatment success rates (cure rate + completed treatment rate), respectively [55]. The results showed worsen outcomes among previously treated patients. Report from the 10th Zonal Tuberculosis and Chest Disease Centre, Chiang Mai, Thailand, in 2011 which had been collected from the data of laboratory-confirmed 254 MDR-TB patients (72.8% of all probable MDR-TB cases) among 349 totally suspected-MDR-TB cases with 15.8% of HIV coinfection in northern Thailand between 2005-2010 gradually increased from 62.2% of probable MDR-TB cases in 2005 to 78.3% in 2010 and revealed 3.2% treatment-denial patients, 75.2% treatment-registered patients, 30.2% died before starting the second-line drug treatment regimens (pyrazinamide, ethambutol, ofloxacin, para-aminosalicylic acid administered for 18-24 months and one injectable drug (kanamycin, or amikacin) administered 5 days per week for the initial 6-month phase), 25.4% default-treatment patients (continuous interruption of treatment more than 2 months), 54.8% treatment success rate, and 22.2% unavailable-data patients [7]. Among 19 cases with pre-treatment death, 10 cases (52.63%) demonstrated HIV co-infection. Extra-pulmonary cases accounted for 2.4% of the laboratory-confirmed cases which was lower than percentage of susceptible extra-pulmonary TB cases in the same area [56]. Four cases with laboratory-confirmed MDR-TB emerged as XDR-TB during treatment [7]. A previous study on outcomes of a daily supervised-MDR-TB treatment regimen which consisted of initial phase of 6-9 months with kanamycin, ofloxacin, cycloserine, ethionamide,

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**Figure 4.** First-attendance chest radiological features of the three patients (A,B,C) with MDR-TB at the 10th Zonal Tu‐ berculosis and Chest Disease Centre, Chiang Mai, Thailand A : Showing bilaterally diffuse lung infiltration with a cavity in the left upper lung zone, B : Showing fibrotic infiltration with surrounding new infiltration at the right upper lung zone with bilaterally diffuse emphysematous lung changes, C : Showing bilaterally diffuse infiltration with a cavity in the right upper lung zone with left pleural effusion.
