National Tuberculosis Control Program in Denmark and the United States: Epidemiologic Basis

Horwitz, O; Edwards, Phyllis Q.; Lowell, Anthony M.

doi:10.2307/4594837

Cited by 15 publications

(4 citation statements)

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“…Even though these large urban areas have a high proportion of patients infected with human immunodeficiency virus (HIV), who are known to be more susceptible to in-fections and at greater risk of latent TB infection rapidly progressing to active disease, these figures greatly exceed general assumptions regarding transmission (~10%; [10]). Both studies concentrating on these big cities are based on the assumptions that deoxyribonucleic acid (DNA) fingerprinting using the IS6110 sequence as a probe provides ac-curate typing of M. tuberculosis isolates and, furthermore, that the identification of cluster strains necessarily implies recent transmission.…”

mentioning

confidence: 87%

Transmission of tuberculosis in the metropolitan area of Zurich: a 3 year survey based on DNA fingerprinting

Pfyffer¹,

Strässle²,

Rose³

et al. 1998

Eur Respir J

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Restriction fragment length polymorphism (RFLP) analysis of Mycobacterium tuberculosis based on the insertion sequence IS6110 has recently been standardized and become an important molecular tool in answering questions such as: 1) transmission of the disease in community [1,2] and international settings [3] as well as via the nosocomial route [4,5]; 2) reactivation versus reinfection of tuberculosis (TB) [6]; and 3) cross contamination of cultures in the laboratory [7].Large population-based studies undertaken in New York [8] and San Francisco [9] utilizing IS6110-based RFLP analyses have revealed clusters, which inferred that recen-tly transmitted TB encompassed 30-40% of TB cases. Even though these large urban areas have a high proportion of patients infected with human immunodeficiency virus (HIV), who are known to be more susceptible to in-fections and at greater risk of latent TB infection rapidly progressing to active disease, these figures greatly exceed general assumptions regarding transmission (~10%; [10]). Both studies concentrating on these big cities are based on the assumptions that deoxyribonucleic acid (DNA) fingerprinting using the IS6110 sequence as a probe provides ac-curate typing of M. tuberculosis isolates and, furthermore, that the identification of cluster strains necessarily implies recent transmission.Most recent concepts of molecular epidemiology utilizing additional genetic markers, such as the polymorphic GC-rich repetitive sequence (PGRS; [11,12]) and/or the 36 base pair (bp) direct repeat (DR; [13,14]) have, however, demonstrated that DNA fingerprinting with the IS-6110 technique was not always sufficient, particularly, in those cases where isolates have fewer than six copies of IS6110 [15][16][17]. Use of supplementary fingerprinting techniques markedly decreased clustering and, thus, put the transmission links suggested by molecular biology more in line with epidemiological data.In the present study RFLP patterns of M. tuberculosis strains isolated from TB patients of the metropolitan area of Zurich (population 1.2 million; area: 1,729 km 2 ) over a period of 3 yrs were analysed to determine the frequency of recent transmission, which eventually reflects the effectiveness of current measures of TB control, i.e., on case finding and management, contact tracing and preventive therapy strategies. Methods Patient populationThe study cohort included 444 patients of the Canton of Zurich, all being treated for TB between 1991 and 1993 (278 males, 166 females; 216 Swiss-born (48.6%), 228 foreign-born (51.4%)). Restriction fragment length polymorphism (RFLP) analysis was performed by using IS6110 and the polymorphic GC-rich sequence (PGRS) as genetic markers. Transmission of tuberculosis in the metropolitan area ofNinety nine isolates shared by 77 patients (21.3%) were associated with 28 IS6110-defined clusters. However, secondary typing of low copy number isolates decreased the number of clusters to 25, encompassing 81 isolates from 63 (17.5%) patients. By deoxyribonucleic acid (DNA) fin...

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confidence: 87%

Transmission of tuberculosis in the metropolitan area of Zurich: a 3 year survey based on DNA fingerprinting

Pfyffer¹,

Strässle²,

Rose³

et al. 1998

Eur Respir J

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“…39:1683, 2001). Other than studies in South East Asian countries, which have reported single-copy strain prevalences of up to 20% (13,22,34), most studies have reported less than 5% single-copy strains (5,16,19,20). Not all IS6110 single-copy isolates are genetically identical or clonal in origin (18).…”

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confidence: 99%

“…The proportion of recently transmitted cases is reported to vary widely from 10% to 58% (3,4,7,8,10,15,17,20,25,26) in developed countries and from 20% to 36% in developing countries (12,16,32). In addition to the relatively low clustering, the transmission pattern may also differ in our setting.…”

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confidence: 99%

Molecular Epidemiology of Tuberculosis in a Rural Area of High Prevalence in South India: Implications for Disease Control and Prevention

et al. 2002

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Molecular and conventional epidemiologic techniques were used to study the mechanisms and risk factors for tuberculosis transmission in a rural area with high prevalence in south India. Restriction fragment length polymorphism analysis with IS6110 and direct repeat probes was performed with 378 Mycobacterium tuberculosis isolates from patients. Forty-one percent of M. tuberculosis isolates harbored a single copy of IS6110. Of 378 patients, 236 had distinct strains; 142 (38%) shared a strain with other patients, indicating recent infection. Older patients, those detected by a house-to-house community survey, and those hospitalized in a sanatorium were more likely to have had a recent infection. These findings suggest that the majority of the tuberculosis cases in south India were due to reactivation; therefore, efforts to control tuberculosis should be sustained.Each year, nearly 3.5 million new cases of infectious tuberculosis (TB) occur worldwide (11). Molecular epidemiologic studies of Mycobacterium tuberculosis strains by using DNA fingerprinting have provided valuable information about the mechanisms of transmission of TB. Most of these studies, however, have been conducted in countries with a low incidence of tuberculosis and usually in urban settings with pockets of high transmission. In such settings, 35 to 50% of new TB cases are the result of recent person-to-person or exogenous transmission (1,12,25). Few molecular epidemiologic studies have been conducted in countries with a high incidence of TB (10,16).India has the highest number of incident TB cases in the world. The limited numbers of molecular epidemiologic studies conducted in India were laboratory based and comprised small numbers of patients (9, 24). Risk factors for exogenous transmission of TB have not been documented in the country. This study combined molecular and conventional epidemiologic techniques to investigate the mechanisms and risk factors for TB transmission in a rural area of high prevalence in south India.The study site was Tiruvallur District, where the world's largest Mycobacterium bovis BCG trial was conducted (28). The total population of the study area is 580,000. The incidence of smear-positive TB is 76 per 100,000 in the population (29). The study subjects were all TB patients undergoing treatment according to the Revised National Tuberculosis Control Program guidelines (21) at one of the 17 primary health centers in the study area from July 1999 to June 2000. Within a week of commencing treatment, two sputum samples were collected from each patient for mycobacterial culture on Lowenstein-Jensen (LJ) medium. The samples that yielded positive cultures were further confirmed to be typical M. tuberculosis strains (2) and tested for drug susceptibility. The DNA extraction and restriction fragment length polymorphism (RFLP) analysis were performed by standard protocols (9,18,24,30). Two investigators independently analyzed the patterns by visual inspection. For quality control, RFLP was repeated with an additional specimen fo...

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“…The open pulmonary tuberculosis patient constitutes a major health hazard wherever he or she is found and is the primary source of new cases of tuberculosis in any community. In the past, strenuous efforts have been made to identify, isolate, and treat such individuals (Styblo, 1980;Horwitz et al , 1973), but such preventive measures are expensive and time consuming and in many communities have been judged to have only limited efficacy (Holm, 1969;Anon., 1982a). However, in some communities it may be the only cost-effective method for controlling the spread of this disease (Hock and Loy, 1981).…”

Section: Pathogenesis Of Mycobacterial Infectionsmentioning

confidence: 99%

Immunology of Mycobacterial Infections

Collins

1988

Infection

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National Tuberculosis Control Program in Denmark and the United States: Epidemiologic Basis

Cited by 15 publications

References 1 publication

Transmission of tuberculosis in the metropolitan area of Zurich: a 3 year survey based on DNA fingerprinting

Transmission of tuberculosis in the metropolitan area of Zurich: a 3 year survey based on DNA fingerprinting

Molecular Epidemiology of Tuberculosis in a Rural Area of High Prevalence in South India: Implications for Disease Control and Prevention

Immunology of Mycobacterial Infections

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