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 ~  Abstract
 ~ Introduction
 ~ Results
 ~ Discussion
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  Table of Contents  
Year : 2016  |  Volume : 34  |  Issue : 3  |  Page : 362-368

Epidemiology and patterns of drug resistance among tuberculosis patients in Northwestern Iran

1 Tuberculosis and Lung Disease Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
2 Department of Hematology, Faculty of Medicine, Tabriz Branch, Islamic Azad University of Tabriz, Tabriz, Iran
3 Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
4 Department of Laboratory Science, Faculty of Para Medicine, Tabriz University of Medical Sciences, Tabriz, Iran

Date of Submission29-Oct-2014
Date of Acceptance30-Jun-2016
Date of Web Publication12-Aug-2016

Correspondence Address:
K Ansarin
Tuberculosis and Lung Disease Research Center, Tabriz University of Medical Sciences, Tabriz
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0255-0857.188352

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 ~ Abstract 

Background: Multidrug-resistant tuberculosis (MDR-TB) has emerged as an important global health concern and is on the rise throughout the world. Objective: The aim of this study was to examine the epidemiology and pattern of TB drug resistance. Methods: In this cross-sectional study, 180 pulmonary TB patients from two Northwestern provinces of Iran were selected. The first and second line drug susceptibility testing was carried out using the 1% proportion method on the Lφwenstein-Jensen medium. Full demographic, environmental and clinical history was evaluated. Results: Prevalence of resistance to any TB drug was 13.8%. Eight (4.4%) patients had MDR-TB (2.4% in the province of East Azerbaijan and 9.3% in the province of Ardabil) and one patient had extensively drug-resistant TB. Patient resistance to both isoniazid and streptomycin was the most prevalent at a rate of 8.3%. Patients showed the least resistance to ethambutol (2.8%). There was a significant relationship between the previous history of TB drug treatment and TB drug resistance. Migrants from rural to urban areas were in high-risk groups for the occurrence of TB drug resistance. Conclusion: In our study, prevalence of MDR was less than the global average. It is essential to monitor the patients with previous history of TB treatment and migrants by rapid and accurate techniques in terms of drug-resistance odds.

Keywords: Drug resistance, epidemiology, tuberculosis

How to cite this article:
Sahebi L, Ansarin K, Seyyedi M, Monfaredan A, Farajnia S, Moaddab S R, Rashedi J. Epidemiology and patterns of drug resistance among tuberculosis patients in Northwestern Iran. Indian J Med Microbiol 2016;34:362-8

How to cite this URL:
Sahebi L, Ansarin K, Seyyedi M, Monfaredan A, Farajnia S, Moaddab S R, Rashedi J. Epidemiology and patterns of drug resistance among tuberculosis patients in Northwestern Iran. Indian J Med Microbiol [serial online] 2016 [cited 2021 Jan 27];34:362-8. Available from:

 ~ Introduction Top

Becoming a global health concern, multidrug-resistant tuberculosis (MDR-TB) is on the rise throughout the world. [1] According to the World Health Organization (WHO) report, about 3.5% of new TB cases and about 21% of retreatment patients were MDR-TB in 2014. [1] MDR-TB is defined as TB that is resistant at least to isoniazid (INH) and rifampicin (RMP). Of the percentage of the group classified as MDR-TB, 9% had extensively drug-resistant-TB (XDR-TB). [2] XDR-TB is classified as resistance to INH, RMP, any antibiotics from the fluoroquinolones and any second-line injectable medications (i.e. amikacin, capreomycin and kanamycin). [3]

New TB cases are defined as patients who had never received treatment for TB or had been on anti-TB treatment for fewer than 4 weeks. Retreatment patients are classified as patients with any form of TB that had been cured for more than 1 month. [1]

Treatment of MDR-TB is a costly and time-consuming process which might be associated with numerous complications. The overall burden of MDR-TB is high and even higher if working days are lost and mortality is taken into account. If left untreated, MDR-TB has an estimated 80% fatality rate. [4]

It is notable that the highest rates of resistance in 2008 have been reported in Eastern Europe and East Mediterranean regions. [5] In Iran, the proportion of MDR-TB cases to new and retreated TB cases was reported to be 5% and 48.0%, respectively. Due to the proximity with countries such as Azerbaijan and Armenia which are among the 27 countries with the high MDR-TB burden in the world, the control of drug resistance is very pivotal in Iran. [6]

The main strategy to control MDR-TB is the detection of drug resistance to prescribe effective medication to patients. The gold standard for detection of MDR-TB is 1% proportion method on LJ medium. Developed in the 1960s, LJ medium is inexpensive and easy to perform. [7]

In the Northwest of Iran, The pattern of TB drug resistance has not been surveyed, and their associated risk factors have not been fully investigated. To control and manage TB, knowledge of drug-resistant TB and associated risk factors are important.

The aim of this study was to identify the patterns of resistance to TB drugs based on 1% proportion technique among pulmonary Mycobacterium tuberculosis (MTB) complex isolates from patients in the Northwest of Iran (East Azerbaijan and Ardabil provinces) and to analyse different environmental, demographic and clinical factors' relationships with drug-resistance.


A cross-sectional study was conducted in two Iranian Northwestern provinces (East Azerbaijan and Ardabil) from April 2011 to March 2013. Assuming a significance level (P = 0.05), prevalence of MDR-TB (P = 0.05) [3] and margin of error (D = 0.018), a sample size of 192 was estimated based on proportional simple random sampling. [4] Considering the likelihood of missing cases, 200 positive smear TB patients were selected from the Northwestern reference laboratory during the study period. The required sample size for each province was determined in proportion to the total number of smear-positive pulmonary TB cases in the provinces. Then, based on TB prevalence in the provinces (in 2010), 147 and 53 native patients were recruited from East Azerbaijan and Ardabil provinces, respectively.

During the study period, 1-2 sputum samples (positive for pulmonary TB) were collected in the province of East Azerbaijan each week and 1-2 sputum (positive pulmonary TB) were collected in the province of Ardabil every 2 weeks. This study was approved by the Medical Ethics Committees of both Tabriz and Ardabil universities; moreover, patients were asked for written informed consent before interviews.

Sputum-positive pulmonary TB is defined as TB in patients with at least two initial sputum smear examinations which tested positive for acid-fast Bacilli (AFB), one sputum smear which tested positive for AFB and radiographic abnormalities consistent with active pulmonary TB or one sputum smear specimen which tested positive for AFB and culture showing positive for MTB.[7] Two smears with the highest bacterial count were cultured on the LJ medium and one culture was selected for a drug susceptibility test. The MTB complex was identified by culturing on LJ medium containing p-nitrobenzoic acid. The samples containing non-MTB were excluded from this study. Drug susceptibility was tested on the LJ medium containing INH: 0.2 mg/l, RMP: 40 mg/l, ethambutol (EMB): 2 mg/l, streptomycin (STM): 4 mg/l and second line drugs including kanamycin: 30 mg/l, capreomycin: 40 mg/l, ofloxacin: 20 mg/l and ciprofloxacin: 2 mg/l according to the proportion method based on WHO/IUTLD guidelines. [7] The data related to demographics (age, gender, job, education, marital status, income, socioeconomic status [SES] and number of children in family), environmental characteristics (number of people in household, house type, age of the building, number of rooms in house and history of migration) and data related to clinical factors (smoking status, alcohol use, narcotic use, instance of chronic disease or diabetes, Bacille Calmette-Guérin [BCG] vaccine history, purified protein derivative [PPD], TB history in family and treatment group) were provided using the information mentioned in the surveying of medical records and with the help of the physician in charge of the treatment of TB as well as personal interviews and home inspections. It should be mentioned that the data of the patients under 15 years were completed with the help of the patients' parents and the information regarding deceased patients was filled in by the closest person to the patient. In a pilot study, the validity of the questionnaire was evaluated as confirmed by expert professors and its reliability was assessed using the statistical reliability test (Cronbach's alpha = 0.92). Univariate and multiple logistic regression was used to compare the effect of demographic, environmental and clinical factors on drug resistance considering a significance level of 0.05 using SPSS 18 software (233 South Wacker Drive, 11 th Floor, Chicago, Ill. USA).

 ~ Results Top

One hundred and eighty-seven cases of 200 patients with MTB had a positive culture and 13 patients had a negative culture [Figure 1]. In the drug resistance analysis sample, seven cultures were contaminated and therefore 180 cases were available for drug resistance analysis. All of the patients were HIV negative (ELISA Test). The overall frequency of new TB and retreatment TB groups was 163 and 17 patients, respectively [Figure 1].
Figure 1: Study sample of patients with Mycobacterium tuberculosis in two provinces of Iran

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The median age of patients available for drug resistance analysis was 53.0 years (range: 6 months to 90 years); 98 patients (54.4%) were male and 126 patients (70%) lived in East Azerbaijan province. Overall, 25 (13.8%) patients (19 patients in East Azerbaijan and 6 patients in Ardabil) had isolates resistant to 1 or more first-line anti-TB drugs and 8 (4.4%) patients were MDR-TB (2.4% in East Azerbaijan and 9.3% in Ardabil). One case (0.79%) of East Azerbaijan patients was XDR [Table 1]. The pattern of drug resistance is demonstrated in [Table 1]. Any resistance to INH (8.3%) and to STM (8.3%) had the highest proportions to TB drugs, whereas EMB showed the least rate of resistance (2.8%) [Table 1]. Eleven percent of new TB cases and 41.8% of retreatment TB cases were resistant to at least one TB drug. In the retreatment TB group, any resistance to INH was 23.5%, RMP: 17%, STM: 11.76% and EMB: 0%. The proportion of mono-drug resistance to TB was estimated at 29.4%. MDR-TB and XDR-TB prevalence was 23.5% and 5.88%, respectively; also, total poly-resistance other than MDR prevalence was 23.5%. Regarding the new TB group, any resistance to INH was 6.74, RMP: 4.2%, EMB: 2.99 and STM: 7.78%. Mono-drug resistance to TB prevalence was 6.59%, also MDR-TB and XDR-TB prevalence was 2.4% and 0%, and total poly-resistance other than MDR was 1.2%. The prevalence of drug resistance for new TB and retreatment TB is shown in [Table 1].
Table 1: Drug resistance pattern among pulmonary Mycobacterium tuberculosis patients in Northwestern Iran

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We compared the demographical, geographical, environmental and clinical factors on resistance to drugs and susceptible patients by univariate and multiple regression logistic tests. In the multiple models, variables with a P 0≤ 0.1 were included and reanalysed. There was not any relation between drug resistance and age (CI 95% 0.93-1.08), female gender (CI 95% 0.06-13.1), SES (CI 95% 0.7-1.29), marital status (CI 95% 0.06-13.1) or the number of children in the family (CI 95% 0.81-1.22). Furthermore, no association was observed between housing type (owned/rented) and drug resistance (CI 95% 0.065-4.43), the age of the building (CI 95% 0.72-1.04) or the number of rooms (CI 95% 0.96-1.04). Regarding clinical characteristics having chronic disease (CI 95% 0.05-10.1), PPD (CI 95% 0.06-16), BCG vaccination history (CI 95% 0.85-1.23) and having a family history of TB (CI 95% 0.46-5.6) did not have relation with drug resistance in patients [Table 2].
Table 2: Analysing of various predictive factors as demographic, geographic and environmental characteristics and clinical characteristics on drugs resistance among pulmonary Mycobacterium tuberculosis patient in Northwestern Iran

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The odds of resistance to one or more TB drugs were significantly high in retreatment cases compared to newly diagnosed cases in univariate (CI 95% 0.06-0.52) and multiple regression analyses (CI 95% 0.004-0.698) [Table 2]. Furthermore, migration history from rural to urban areas increased the odds of drug resistance (CI 95% 1.08-9.07) in univariate regression analysis [Table 2].

 ~ Discussion Top

Incidences of MDR-TB have increased in the past few decades. [3] According to the global project on anti-TB drug resistance surveillance, the average prevalence of resistance to any drug was 11.1% and 25.1% in new and previously treated cases, respectively. [2] As a result, in comparison with our findings (11.04% and 41.8% in new and previously treated cases, respectively), any drug resistance proportion in new cases was similar to the global estimates, whereas secondary drug resistance was about 1.6 times of the global rate. It seems that the Northwest of Iran has a moderate drug resistance rate in new cases compared to global estimates, but its proximity to country of Azerbaijan (with a prevalence of 56.3% and 84.4% drug resistance in new and previously treated cases) [2] necessitates the task of controlling drug resistance in this region. In comparison to our study, lower MDR-TB rates of previously treated cases (2% for new cases and 24.9% for previously treated) were reported from the WHO Eastern Mediterranean region. [5]

We summarised the patterns of TB drug resistance for 14 different countries. [Table 3] demonstrates the proportion of TB drug resistance in ours and other studies clearly. [3],[5],[2],[8],[9],[10],[11],[12],[13],[14],[15] According to [Table 3], the average of MDR-TB prevalence in Iran was 18.3%. [12],[16] It should be noted; our study was the first study of its kind conducted in the Northwest of Iran. The discrepancy of drug resistance with other Iranian studies can be explained by the diversities in the source population. In the available studies from Iran, the study samples were comprised Iranian and Afghan patients. [15],[16],[17] As reported by the WHO global project over 1999-2002, Afghan patients comprised a high percentage of the MDR-TB cases in Iran. [18] We screened and sampled solely Iranians in this study. In addition, different sample sizes and time periods in other seem to have changed the validity of findings.
Table 3: Proportion of tuberculosis drug resistance of 14 different countries

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We found that a case of XDR among MDR-TB patients should serve as a warning sign. XDR-TB is documented in 2006 in Iran (10.9% of MDR-TB strains). [17] XDR-TB has been reported from 84 countries (with a range of prevalence from 4% in Armenia to 23.7% in Estonia). [2] In our study, the prevalence of drug resistance was the highest for STM and INH following by RMP and EMB. This result is almost consistent with other Iranian studies. [12],[13],[14],[15],[16],[17]

Knowledge of drug resistance patterns for new and previously treated cases is critical for effective control of MDR-TB in different regions in Iran. There is a well-established relation between the proportion of retreatment cases and MDR-TB. [13] In this study, we observed a strong relation between the treatment group and drug resistance by multiple regression logistic analysis. The relation between history of receiving anti-TB treatment and drug resistance has been clearly described in several studies. [3],[5],[8],[9],[10],[15],[16],[19] Hence, previous treatment is one of the most important risk factors for the development of drug-resistant TB. [10]

Immigration has been suggested as a leading factor in the increasing prevalence of MDR-TB in some countries. [11],[20] In this study, there was an association between resistant TB and migration from rural to urban areas as well.

Different studies in the analysis of various factors association as, clinical, environmental and demographic factors with drug resistance have yielded conflicting results. We found no association between age and TB drug resistance. The findings in other studies [8],[9] were consistent with our study. However, these findings were contradictory to some reported studies. [10],[16],[13]

In the assessment of gender, smoking status, SES and diabetes mellitus history, none of the variables showed a significant association with the drug resistance. These findings were in accordance with the results of studies in Indonesia [8] and Georgia. [10] Although some of studies reported males had higher rates of TB drug resistance, [9],[5] also Khoharo and Shaikh in Pakistan [3] reported that the odds of TB drug resistance were significantly higher in diabetic patients. Merza et al. [9] reported that unemployment in patients has a significant relationship with TB drug resistance as well.

None of the environmental factors, such as the ownership of a house and the number of rooms per house, were associated with the TB drug resistance in this study. A national study reported patients that did not own a house had a higher odd of contracting MDR-TB. Due to a lack of studies in this field, extensive comparison was not possible. [21]

We did not find a significant relationship between BCG vaccination and TB drug resistance. Accessible studies on the effect of vaccination on drug resistance are very low. Of limitation in this study was its small sample size.

 ~ Conclusion Top

In our study, the prevalence of drug resistance was the highest for STM and INH. The Northwest region of Iran had a moderate drug resistance rate in new cases, whereas drug resistance rate in previously treated cases was more than of 1.5 times of global rate. The burden of MDR-TB in retreatment cases and patients with an immigration history was high, and it seems necessary to monitor these groups of patients by rapid and accurate techniques in terms of drug-resistance odds.

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Conflicts of interest

There are no conflicts of interest.

 ~ References Top

World Health Organization. WHO Global Tuberculosis Report 2014. Drug Resistance TB. Surveillance & Response; 2014. Available from: [Last accessed on 2015 Aug 04].  Back to cited text no. 1
Wright A, Zignol M, Van Deun A, Falzon D, Gerdes SR, Feldman K, et al. Epidemiology of antituberculosis drug resistance 2002-07: An updated analysis of the global project on anti-tuberculosis drug resistance surveillance. Lancet 2009;373:1861-73.  Back to cited text no. 2
Khoharo HK, Shaikh IA. Drug resistance patterns in pulmonary tuberculosis. J Pak Med Assoc 2011;61:229-32.  Back to cited text no. 3
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Mdivani N, Zangaladze E, Volkova N, Kourbatova E, Jibuti T, Shubladze N, et al. High prevalence of multidrug-resistant tuberculosis in Georgia. Int J Infect Dis 2008;12:635-44.  Back to cited text no. 10
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Mansoori SD, Arami S, Mirabolhasani Z, Farnia P, Velayati AA. Pattern of drug resistance among newly diagnosed and old cases of pulmonary tuberculosis in NRITLD. Arch Iran Med 2003;6:255-60.  Back to cited text no. 15
Merza MA, Farnia P, Tabarsi P, Khazampour M, Masjedi MR, Velayati AA. Anti-tuberculosis drug resistance and associated risk factors in a tertiary level TB center in Iran: A retrospective analysis. J Infect Dev Ctries 2011;5:511-9.  Back to cited text no. 16
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Ramazanzadeh R, Farnia P, Amirmozafari N, Ghazi F, Ghadertotonchi Z, Kamran J, et al. Comparison between molecular epidemiology, geographical regions and drug resistance in Mycobacterium tuberculosis strains isolated from Iranian and Afghan patients. Chemotherapy 2006;52:316-20.  Back to cited text no. 18
Espinal MA, Laszlo A, Simonsen L, Boulahbal F, Kim SJ, Reniero A, et al. Global trends in resistance to antituberculosis drugs. World Health Organization-International Union against Tuberculosis and Lung Disease Working Group on Anti-Tuberculosis Drug Resistance Surveillance. N Engl J Med 2001;344:1294-303.  Back to cited text no. 19
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Ulmasova DJ, Uzakova G, Tillyashayhov MN, Turaev L, van Gemert W, Hoffmann H, et al. Multidrug-resistant tuberculosis in Uzbekistan: Results of a nationwide survey, 2010 to 2011. Euro Surveill 2013;18. pii: 20609.  Back to cited text no. 21


  [Figure 1]

  [Table 1], [Table 2], [Table 3]


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