Previous Article | Next Article 
Journal of Clinical Microbiology, May 2009, p. 1338-1343, Vol. 47, No. 5
0095-1137/09/$08.00+0 doi:10.1128/JCM.02490-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Mycobacterium tuberculosis Transmission Is Not Related to Household Genotype in a Setting of High Endemicity
B. J. Marais,1,2*
A. C. Hesseling,2
H. S. Schaaf,1,2
R. P. Gie,1,2
P. D. van Helden,2,3 and
R. M. Warren2,3
Department of Paediatrics and Child Health, Tygerberg Children's Hospital,1 Desmond Tutu Tuberculosis Research Centre, Stellenbosch University, Tygerberg, South Africa,2 DST/NRF Centre of Excellence in Biomedical Tuberculosis Research/MRC Centre for Molecular Biology and Human Genetics, Department of Biomedical Sciences, Stellenbosch University, Tygerberg, South Africa3
Received 26 December 2008/ Returned for modification 4 February 2009/ Accepted 17 February 2009
Among the different strains of Mycobacterium tuberculosis, Beijing has been identified as an emerging genotype. Enhanced transmissibility provides a potential mechanism for genotype selection. This study evaluated whether the Beijing genotype is more readily transmitted than other prevalent genotypes to children in contact with an adult tuberculosis (TB) index case in the child's household. We conducted a prospective, community-based study at two primary health care clinics in Cape Town, South Africa, from January 2003 through December 2004. Bacteriologically confirmed new adult pulmonary TB cases were genotyped by IS6110 DNA fingerprinting; household contacts less than 5 years were traced and screened for M. tuberculosis infection and/or disease. A total of 187 adult index cases were identified from 174 households with children aged less than 5 years. Of 261 child contacts aged 0 to 5 years, 219 (83.9%) were completely evaluated and the isolate from the index case was successfully genotyped. M. tuberculosis infection (induration of 
10 mm by Mantoux tuberculin skin test) was documented in 118/219 (53.9%) children; 34 (15.5%) had radiographic signs suggestive of active TB. There was no significant difference in the ratio of infected children among those exposed to the Beijing genotype (51/89; 57.3%) and those exposed to non-Beijing genotypes (55/115; 47.8%) (odds ratio, 1.5; 95% confidence interval, 0.8 to 2.7). Genotyping was successful for six children diagnosed with active TB; the isolates from only two children had IS6110 fingerprints that were identical to the IS6110 fingerprint of the isolate from the presumed index case. We found no significant association between the M. tuberculosis genotype and transmissibility within the household. However, undocumented M. tuberculosis exposure may have been a major confounding factor in this setting with a high burden of TB.
* Corresponding author. Mailing address: Department of Paediatrics and Child Health, Faculty of Health Sciences, Stellenbosch University, P.O. Box 19063, Tygerberg 7505, South Africa. Phone: 27-21-938 9155. Fax: 27-21-838 9138. E-mail: bjmarais{at}sun.ac.za
Published ahead of print on 4 March 2009.
Journal of Clinical Microbiology, May 2009, p. 1338-1343, Vol. 47, No. 5
0095-1137/09/$08.00+0 doi:10.1128/JCM.02490-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»