Evaluation of tuberculosis transmission in Tehran: using RFLP and spoloigotyping methods
Introduction
According to East Mediterranean Regional office (EMRO) records, the estimated incidence rate of tuberculosis in Tehran (with approximately 12 million population) was 12–16 per 100 000.1 Whereas, the notification rate was less than 70%.2 This means considerable numbers of TB patients are missed in the early stages of diseases. Each of these patients soon develop more extensive disease and themselves become new vectors of transmission. Therefore, the low case detection system might increase the risk of TB infection through active transmission. Previous studies3., 4. showed that 90% of active cases of tuberculosis in Iran resulted from reactivation of an infection contracted years before and that recently transmitted diseases had a minor role. In Iran, the TB surveillance is generally performed by conventional methods.5 The sum of information about sex/age/foreign/non-foreign/part of body involved/pervious history/close contact and microbiological confirmation tests are collected from various public health offices at the district level and send to the statistical office of the TB control manager.5 Further, analysing the data would determine the percentage of exposure, infection and death from diseases inside the country. The method has limited practical value because it cannot identify the source and the route of infection and cannot discriminate between new and old infection. Thereby, for identifying the M. tuberculosis strains which are responsible for multiple infection, presumably through recent transmission as well as the strains found in only one TB patient, presumably representing reactivation of latent infection the IS6110-RFLP and spoligotyping were performed. The IS6110-RFLP is based on the observation that RFLP patterns among non-epidemiologically related isolates show a high degree of variation, whereas epidemiological related M. tuberculosis strains show identical or similar fingerprint patterns.6., 7., 8. However, since RFLP analysis with IS6110 alone may be inconclusive for strains carrying few copies of IS6110,9., 10. we also used an alternative PCR-based technique called spoligotyping.11 The technique detects various non-repetitive spacer sequences located between small repetitive units (direct repeat DR) in the chromosome of M. tuberculosis complex. The spacer sequences are a source of diversity that can be use for detecting polymorphism among M. tuberculosis complex.12 In this study, we focused on Iran-born TB patients who were residing in Tehran and had no prior history of tuberculosis treatment.
Section snippets
Data collection
The study was conducted from January to December 2001. Case data were collected by trained technicians using standard questionnaires. Information was obtained on sex, age, country of birth, close contact, previous TB history, present address and associated medical data, such as human immunodeficiency virus (HIV) infection, tuberculin skin test and chest radiography finding.
Bacterial strains
Primary isolation and culturing of Mycobacterium isolates from sputum specimens were followed in accordance to procedures
Characteristics of the Patients
Of the initial 218 patients with pulmonary TB, 89 (40.8%) were excluded because the patients were from retreatment cases or they were Afghan-born immigrants. The study group, therefore, consisted of 129 Iranian cases (59%) with no prior history of tuberculosis. All of them were incidents of in Tehran during the last 10 years. The patients were between 18 and 95 years old. The male to female ratio was 1.2:1. One hundred and eleven patients had (86%) in ratios susceptible to all four drugs
Discussion
The major consideration of the usefulness of the IS6110-RFLP typing method is its specificity6., 8. which is depends on the number of bands obtained. Previously,3 we found 38% of M. tuberculosis strains with low or no copies of IS6110. These strains were collected from Khorasan province which is 930 km in north east of Tehran. In the present study, only seven strains (5.4%) were found with low or no copies of IS6110. Whereas, the remaining isolates (94.5%) contained more than six copies.
Acknowledgements
This work was supported by a grant from UNESCO-IUMS Mircens-SGM short-term fellowship We gratefully thanks Center of National de Reference des Mycobateries, Institute Pasteur, Paris (France) for providing all chemicals and Laboratory facilities.
References (26)
- et al.
Differences in the prevalence of IS6110 insertion sites in M. tuberculosis strains: low and high copy number of IS6110
Tub Lung Dis
(1998) - Ministry of Health and Medical Education. Iran: Diseases Control Unit,...
- Global Tuberculosis Control. Geneva, Switzerland: World Health Organization (WHO),...
- et al.
Transmission pattern of tuberculosis using RFLP-based IS6110
Arch Irn Med
(2001) - et al.
IS6110-RFLP and spoligotyping of Mycobacterium tuberculosis isolates in Iran
Scand J Infect Dis
(2000) - (1998)
- et al.
Strain identification of Mycobacterium tuberculosis by DNA fingerprinting : recommendations for a standardized methodology
J Clin Microbiol
(1999) - et al.
Molecular epidemiology of tuberculosis in the Netherlands: a national wide study from 1993 through 1997
J Infect Dis
(1999) - et al.
Epidemiology of tuberculosis in Hamburg, Germany: long-term population-based analysis applying classical and molecular epidemiological techniques
J Clin Microbiol
(2002) - et al.
IS6110-RFLP typing of clinical isolates of M. tuberculosis in Madras, South India
Tub Lung Dis
(1993)
Simultaneous detection and strain differentiation of M. tuberculosis for diagnosis and epidemiology
J Clin Microbiol
Spoligotyping followed by doubled-repetitive elements PCR as rapid alternative to IS6110 fingerprinting for epidemiological studies of tuberculosis
J Clin Microbiol
Public Health Mycobacteriology: a guide for a level III laboratory
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