Pulmonary tuberculosis in Harare, Zimbabwe: analysis by spoligotyping

Abstract

Background-Over the last 10 years there has been a fourfold increase in cases of tuberculosis in Harare, Zimbabwe. The use of molecular epidemiology to understand tuberculosis transmission in this epidemic has been hampered by the availability of suitable culture facilities. A study was therefore undertaken to explore the potential of spoligotyping, a polymerase chain reaction based technique that does not require tuberculosis culture. Methods-Adults attending a chest clinic with clinical or radiological pulmonary tuberculosis and one smear positive sputum were enrolled over one month. Demographic, socioeconomic, and clinical data were gathered using a standardised questionnaire. Molecular fingerprinting of genomic DNA recovered from sputum was performed by spoligotyping. Results-Sixty one subjects (median age 28 years (range 18-73); 61% men) were recruited and 57 provided adequate sputum samples. Recent rural-urban migration or immigration was not common; 40% of subjects lived in crowded living conditions. DNA suitable for spoligotyping was recovered from 28 patients and 20 diVerent genotypes of Mycobacterium tuberculosis were identified. Fifteen patients were infected with an M tuberculosis strain shared by one or more individuals. Patients infected with a shared spoligotype were not closely linked geographically within Harare, but were more likely to live in overcrowded conditions (69% versus 23%; odds ratio 6.85 (95% CI 1.2 to 47), p = 0.026). Analysis of the patients' original rural family homes revealed two geographically related spoligotype clusters. Conclusions-Spoligotyping may yield valuable molecular typing information in populations where tuberculosis culture is not available. This novel technique requires further development and evaluation in larger epidemiological studies. (Thorax 1998;53:346-350)

High Rates of Clustering of Strains Causing Tuberculosis in Harare, Zimbabwe: a Molecular Epidemiological Study

“…This is substantially higher than the estimates of recent transmission reported from other studies. The proportions of new cases due to recent infection have been estimated in cities and countries where the rates of endemic TB are low and have been found to be 38 to (20) and 50% of 371 patients (42) in South Africa; 62% of patients in Tunisia (24); and 53.6% of 28 TB patients in a small study conducted in Harare in 1995 (25). Our high rate of clustering suggesting recent transmission probably reflects the high prevalence of HIV infection (74%) in our urban population and the relatively young age (median age, 31 years) of our urban population living in generally overcrowded, high-density housing.…”

“…However, there are few data to support this, as few detailed molecular epidemiological studies have been undertaken in countries with high rates of both TB and HIV infection. It has been shown that despite the more limited strain diversity in sub-Saharan Africa, there is still adequate strain variability among M. tuberculosis isolates from patients living in developing countries to permit the application of molecular approaches to the tracking of TB transmission (24,25). Our objectives were, first, to examine the pattern of TB transmission (i.e., the relative frequency of reactivation versus that of recent infection) and the role of HIV infection using two molecular typing methods, spoligotyping and analysis of VNTRs, in tandem with epidemiological data and, second, to identify the risk factors for recent transmission in a well-characterized cohort of smear-positive TB patients in Harare, Zimbabwe.…”

Evaluation and Utilization as a Public Health Tool of a National Molecular Epidemiological Tuberculosis Outbreak Database within the United Kingdom from 1997 to 2001

“…298-PA 02, 1997. ), to 32% of 239 TB patients in San Paulo, Brazil, of whom approximately half were HIV infected (18), 25% of 84 patients in Honduras (37), 33% of 51 patients in Guadeloupe (41), 45% of 38 patients in Havana, Cuba (34), 41% in a study of 41 HIVpositive TB patients from Nairobi, Kenya (26), 45% of 246 isolates clustered in South Africa (48), 62% in Tunisia (28), and 53.6% in a small study of 28 TB patients in Harare, Zimbabwe (30). In a recent study, using a combination of spoligotyping and VNTR on isolates from Harare, Zimbabwe, 78.6% of 187 patients were identified as being part of a cluster (P. J. Easterbrook, A. L. Gibson, and F. A. Drobniewski, unpublished results); this high rate of clustering suggested a high rate of recent transmission.…”

“…Combinations of these methods may prove as discriminating as RFLP IS6110. Some methods such as spoligotyping have added value in that they are able to identify to subspecies level M. bovis BCG and M. tuberculosis and can be used to analyze dead cultures, smear-positive smears, and formalin-fixed specimens (30,32). They aid in our understanding of evolution at the molecular level.…”

“…In general, RFLP methods are the most discriminating (32) but are slow, as they require viable organisms and, as there is no amplification stage, sufficient mycobacterial growth to extract enough DNA for analysis. More-rapid techniques employ a nucleic acid amplification step first (which is usually PCR) and so can be performed on cultures with little bacterial growth, on nonviable organisms, or with limited success, on heavily smear-positive sputum (30,47). The principal methods are divided into those such as spaceroligonucleotide typing (spoligotyping) (31) and variable number tandem repeat (VNTR) (24), which can be codified and stored electronically for comparative purposes, and rapid and/ or arbitrary primed methods.…”