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Open Access Research article

DNA restriction fragment length polymorphism analysis of Mycobacterium tuberculosis isolates from HIV-seropositive and HIV-seronegative patients in Kampala, Uganda

Benon B Asiimwe12, Moses L Joloba2, Solomon Ghebremichael13, Tuija Koivula4, David P Kateete2, Fred A Katabazi2, Alexander Pennhag3, Ramona Petersson3 and Gunilla Kallenius13*

Author Affiliations

1 Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77, Stockholm, Sweden

2 Department of Medical Microbiology, Makerere University Medical School, P O Box 7072, Kampala, Uganda

3 Department of Bacteriology, Swedish Institute for Infectious Diseases Control, SE-171 82, Solna, Sweden

4 Centre for Microbiological Preparedness, Swedish Institute for Infectious Diseases Control, SE-171 82, Solna, Sweden

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BMC Infectious Diseases 2009, 9:12  doi:10.1186/1471-2334-9-12

Published: 5 February 2009

Abstract

Background

The identification and differentiation of strains of Mycobacterium tuberculosis by DNA fingerprinting has provided a better understanding of the epidemiology and tracing the transmission of tuberculosis. We set out to determine if there was a relationship between the risk of belonging to a group of tuberculosis patients with identical mycobacterial DNA fingerprint patterns and the HIV sero-status of the individuals in a high TB incidence peri-urban setting of Kampala, Uganda.

Methods

One hundred eighty three isolates of Mycobacterium tuberculosis from 80 HIV seropositive and 103 HIV seronegative patients were fingerprinted by standard IS6110-RFLP. Using the BioNumerics software, strains were considered to be clustered if at least one other patient had an isolate with identical RFLP pattern.

Results

One hundred and eighteen different fingerprint patterns were obtained from the 183 isolates. There were 34 clusters containing 54% (99/183) of the patients (average cluster size of 2.9), and a majority (96.2%) of the strains possessed a high copy number (≥ 5 copies) of the IS6110 element. When strains with <5 bands were excluded from the analysis, 50.3% (92/183) were clustered, and there was no difference in the level of diversity of DNA fingerprints observed in the two sero-groups (adjusted odds ratio [aOR] 0.85, 95%CI 0.46–1.56, P = 0.615), patients aged <40 years (aOR 0.53, 95%CI 0.25–1.12, P = 0.100), and sex (aOR 1.12, 95%CI 0.60–2.06, P = 0.715).

Conclusion

The sample showed evidence of a high prevalence of recent transmission with a high average cluster size, but infection with an isolate with a fingerprint found to be part of a cluster was not associated with any demographic or clinical characteristics, including HIV status.