Research article

The Recent-Transmission of Mycobacterium tuberculosis Strains among Iranian and Afghan Relapse Cases: a DNA-fingerprinting using RFLP and spoligotyping

Parissa-Farnia , Mohammad Reza Masjedi , Mohammad Varahram , Mehdi Mirsaeidi , Mojtaba Ahmadi , Mehdi Khazampour , Payam Tabarsi , Parvaneh Baghei , Mojtaba Marjane , Muslam Bahadori , Abolhasan Zia Zarifi and Ali Akbar Velayati

Mycobacteriology Research Centre, Iranian National Reference TB Laboratory, National Research Institute Of Tuberculosis and Lung Disease (NRITLD), Shaheed Bahesti University of Medical Sciences(Medical Campus), Shaheed Bahonar Ave, Darabad, Tehran, 19556, P.O: 19575/154, Iran

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BMC Infectious Diseases 2008, 8:109doi:10.1186/1471-2334-8-109

Published:	6 August 2008

Abstract

Background

Relapse of tuberculosis (TB) may develop as the result of reactivation of the endogenous primary infection, or as a result of a exogenous reinfection. This survey evaluated the rate of reactivation versus recent transmission among Iranian and Afghan relapse cases.

Methods

The sputum specimens were digested, examined microscopically for acid-fast bacilli, and inoculated into Löwenstein-Jensen slants by standard procedures. Thereafter, the susceptibility and identification tests were performed on culture positive specimens. Subsequently, the strains that were identified as Mycobacterium tuberculosis (258 isolates) were subjected to IS6110 restriction fragment length polymorphism (RFLP) and spoligotyping. Additional patient's information was collected for further epidemiological analysis. Patients whose isolates had identical genotyping patterns were considered a cluster with recent transmission episode.

Results

Out of 258 available isolates, 72(28%) had multi-drug resistant (MDR-TB) in ratio and 42 (16.2%) had other resistant. Notably, 38 of MDR-TB cases (52%) were isolated from Afghan patients. By IS6110-RFLP typing method, 65 patients (25%) were clustered in 29 clusters. In cluster cases, the intra-community transmissions between Iranian and Afghan patients were 41%. All MDR-TB patients in clusters had either Haarlem I or Beijing characteristic. The risk factors like sex, family history, close contact, living condition, PPD test result and site of TB infection were not associated with clustering. Although, the MDR-TB strains were more frequent in non-cluster cases (31%) than cluster one(18%) (P < 0.05). Majority of M. tuberculosis strains isolated from non-cluster cases were belong to EAI3 (51; 30%) and CASI(32;18.6%) superfamilies.

Conclusion

During the studied period, reactivation of a previous infection remain the more probable cause of recurrence. Although, the evidence of intra- community transmission between Iranian and Afghan TB cases, highlighted the impact of afghan immigrants in national tuberculosis control program (NTP) of Iran.