Characterisation of multidrug-resistant Mycobacterium tuberculosis isolates from Johannesburg, South Africa, by spoligotyping

Abstract number: 1733_1332

Mlambo C., Warren R., Victor T., Duse A., Streicher E., Marais E.

Objective: The development of drug resistance and the emergence of multidrug-resistant tuberculosis (MDR-TB) is a threat to TB control globally. The estimated proportion of MDR-TB cases in South Africa ranges from a median of 1.6% (range 1–2.6%) among new cases to a median of 6.6% (range 4–13.9%) among re-treatment cases, depending on the Province. There is however, limited information on Mycobacterium tuberculosis genotypes currently circulating in the country. The objective of the study was to determine the population structure of MDR-TB strains in the greater Johannesburg area, using molecular techniques.

Methods: Spacer oligonucleotide typing (spoligotyping) was used to analyse 270 consecutive MDR-TB isolates collected from June 2004 to February 2006 at the National Health Laboratory Service TB division, which receives the bulk of samples in the region. The spoligotyping results were compared to the World Spoligotyping Database of the Institut Pasteur de Guadelope.

Results: A total of 247 (92%) different spoligotypes were found in the spoligotyping database, whereas the remaining 23 (8%) were orphan types. A major proportion of the strains (23%) belonged to the LAM family. The proportions of the strains that belonged to the remaining families are as follows: 20% to T, 14% to Beijing, 9% to EAI and 8% to the S/F28 family. The remaining strains belonged either to the CAS family, X family or the U family. Strains from the Beijing family are spread throughout the world and are often associated with drug resistance.

The drugs recommended for treatment of TB in South Africa are isoniazid, rifampicin, ethambutol and streptomycin. Our study showed that the majority of strains (57%) from patients who have MDR-TB were resistant to all the first-line drugs.

Conclusion: This is the first study to detail the molecular types of MDR-TB strains in Johannesburg. It highlights the diversity of the strains that are circulating in the area and the high proportion of MDR-TB strains that are resistant to all the first line anti-TB drugs. These findings could have a significant impact on TB disease control programmes in the region, especially as these strains are the precursors to extensively resistant strains (XDR TB).