Mycobacterium tuberculosis transmission is not related to household genotype in a setting of high endemicity
Date
2009
Authors
Marais B.J.
Hesseling A.C.
Schaaf H.S.
Gie R.P.
Van Helden P.D.
Warren R.M.
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
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. Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Description
Keywords
isoniazid, pyrazinamide, rifampicin, adolescent, adult, article, bacterial strain, bacterial transmission, bacterium isolate, child, controlled study, DNA fingerprinting, endemic disease, genotype, health center, household, human, infant, lung tuberculosis, Mycobacterium tuberculosis, preschool child, prevalence, priority journal, screening test, skin induration, South Africa, thorax radiography, tuberculin test, Adolescent, Adult, Aged, Aged, 80 and over, Child, Preschool, DNA Fingerprinting, DNA, Bacterial, Family Health, Genotype, Humans, Infant, Infant, Newborn, Infectious Disease Transmission, Vertical, Middle Aged, Mycobacterium tuberculosis, South Africa, Tuberculosis, Young Adult, Mycobacterium tuberculosis
Citation
Journal of Clinical Microbiology
47
5
47
5