Genotyping analyses of tuberculosis cases in U.S.- and foreign-born Massachusetts residents

State-level prevalence estimates of latent tuberculosis infection in the United States by medical risk factors, demographic characteristics and nativity

INTRODUCTION

Preventing tuberculosis (TB) disease requires treatment of latent TB infection (LTBI) as well as prevention of person-to-person transmission. We estimated the LTBI prevalence for the entire United States and for each state by medical risk factors, age, and race/ethnicity, both in the total population and stratified by nativity.

METHODS

We created a mathematical model using all incident TB disease cases during 2013-2017 reported to the National Tuberculosis Surveillance System that were classified using genotype-based methods or imputation as not attributed to recent TB transmission. Using the annual average number of TB cases among US-born and non-US-born persons by medical risk factor, age group, and race/ethnicity, we applied population-specific reactivation rates (and corresponding 95% confidence intervals [CI]) to back-calculate the estimated prevalence of untreated LTBI in each population for the United States and for each of the 50 states and the District of Columbia in 2015.

RESULTS

We estimated that 2.7% (CI: 2.6%-2.8%) of the U.S. population, or 8.6 (CI: 8.3-8.8) million people, were living with LTBI in 2015. Estimated LTBI prevalence among US-born persons was 1.0% (CI: 1.0%-1.1%) and among non-US-born persons was 13.9% (CI: 13.5%-14.3%). Among US-born persons, the highest LTBI prevalence was in persons aged ≥65 years (2.1%) and in persons of non-Hispanic Black race/ethnicity (3.1%). Among non-US-born persons, the highest LTBI prevalence was estimated in persons aged 45-64 years (16.3%) and persons of Asian and other racial/ethnic groups (19.1%).

CONCLUSIONS

Our estimations of the prevalence of LTBI by medical risk factors and demographic characteristics for each state could facilitate planning for testing and treatment interventions to eliminate TB in the United States. Our back-calculation method feasibly estimates untreated LTBI prevalence and can be updated using future TB disease case counts at the state or national level.

A genotypic and spatial epidemiologic analysis of Massachusetts' Mycobacterium tuberculosis cases from 2012 to 2015

BACKGROUND

Massachusetts had a rate of 2.8 cases of tuberculosis (TB) per 100,000 individuals in 2015. Although TB in Massachusetts is on the decline, the case rate remains far above the 2020 National TB Target of 1.4 per 100,000. To reduce the TB case rate in Massachusetts, it is necessary to understand the local epidemiology and transmission risks.

METHODS

We used an existing TB case database of Massachusetts TB cases in the time frame from 2012 to 2015, which links de-identified patient demographic information with TB genotypes obtained from the United States Centers for Disease Control and Prevention's (CDC) TB Genotyping Information Management System database. Two or more cases with identical genotypes, which were close in space (within 50 km), as determined in a geographic information system (GIS), and time (3 years), were considered TB clusters.

RESULTS

We analyzed 543 genotyped cases. We identified a total of 85 cases that met the TB cluster criteria, and a total of 33 clusters. US-born individuals (p = 0.003), homeless individuals (p = 0.001) and those reporting illicit substance use (p = 0.001) and alcohol use (p = 0.001) were more likely to appear in a TB cluster.

CONCLUSION

Through a combined genotypic and spatial epidemiological approach, we identified populations and individuals more likely to be in a TB cluster. Testing populations identified as at risk for being in a TB cluster, and providing appropriate treatment, may decrease the overall TB case rate and support efforts to achieve national 2020 TB targets.

Estimated rate of reactivation of latent tuberculosis infection in the United States, overall and by population subgroup

We estimated the rate of reactivation tuberculosis (TB) in the United States, overall and by population subgroup, using data on TB cases and Mycobacterium tuberculosis isolate genotyping reported to the Centers for Disease Control and Prevention during 2006-2008. The rate of reactivation TB was defined as the number of non-genotypically clustered TB cases divided by the number of person-years at risk for reactivation due to prevalent latent TB infection (LTBI). LTBI was ascertained from tuberculin skin tests given during the 1999-2000 National Health and Nutrition Examination Survey. Clustering of TB cases was determined using TB genotyping data collected by the Centers for Disease Control and Prevention and analyzed via spatial scan statistic. Of the 39,920 TB cases reported during 2006-2008, 79.7% were attributed to reactivation. The overall rate of reactivation TB among persons with LTBI was estimated as 0.084 (95% confidence interval (CI): 0.083, 0.085) cases per 100 person-years. Rates among persons with and without human immunodeficiency virus coinfection were 1.82 (95% CI: 1.74, 1.89) and 0.073 (95% CI: 0.070, 0.075) cases per 100 person-years, respectively. The rate of reactivation TB among persons with LTBI was higher among foreign-born persons (0.098 cases/100 person-years; 95% CI: 0.096, 0.10) than among persons born in the United States (0.082 cases/100 person-years; 95% CI: 0.080, 0.083). Differences in rates of TB reactivation across subgroups support current recommendations for targeted testing and treatment of LTBI.

Use of tuberculosis genotyping for postoutbreak monitoring

CONTEXT

Review of routinely collected tuberculosis genotyping results following a known outbreak is a potential mechanism to examine the effectiveness of outbreak control measures.

OBJECTIVE

To assess differences in characteristics between outbreak and postoutbreak tuberculosis cases.

DESIGN

Retrospective.

SETTING

United States.

PARTICIPANTS

All tuberculosis cases identified as a result of >5-person outbreaks investigated by the Centers for Disease Control and Prevention during 2003 to 2007 (original outbreak cases), and subsequent culture-positive tuberculosis cases with matching Mycobacterium tuberculosis genotypes reported in the same county during 2004 to 2008 (postoutbreak cases).

MAIN OUTCOME MEASURE

Proportion of demographic, social, and clinical characteristics of tuberculosis outbreak cases compared to postoutbreak cases. SECONDARY: Proportion of demographic, social, and clinical characteristics of epidemiologically linked versus nonlinked cases.

RESULTS

Six outbreaks with 111 outbreak cases and 110 postoutbreak cases were identified. Differences between outbreak and postoutbreak cases were gender (69% vs 85% male; P < .01), birth origin (3% vs 11% foreign-born; P = .02), disease severity (48% vs 62% sputum smear-positive; P = .04), homelessness (38% vs 51%; P = .05), and injection drug use (4% vs 11%; P = .04). For 5 of the 6 outbreaks, the status of epidemiologic relationships among postoutbreak cases was available (n = 89). The postoutbreak cases with a known epidemiologic link to the original outbreak were in younger persons (aged 39 vs 47 years; P < .01), and a larger proportion reported injection drug use (18% vs 4%; P = .04) or noninjection drug use (44% vs 18%; P < .01) than those without a reported link.

CONCLUSIONS

Health jurisdictions can utilize genotyping data to monitor and define the characteristics of postoutbreak cases related to the original outbreak.

A national study of socioeconomic status and tuberculosis rates by country of birth, United States, 1996-2005

BACKGROUND

Tuberculosis (TB) in developed countries has historically been associated with poverty and low socioeconomic status (SES). In the past quarter century, TB in the United States has changed from primarily a disease of native-born to primarily a disease of foreign-born persons, who accounted for more than 60% of newly-diagnosed TB cases in 2010. The purpose of this study was to assess the association of SES with rates of TB in U.S.-born and foreign-born persons in the United States, overall and for the five most common foreign countries of origin.

METHODS

National TB surveillance data for 1996-2005 was linked with ZIP Code-level measures of SES (crowding, unemployment, education, and income) from U.S. Census 2000. ZIP Codes were grouped into quartiles from low SES to high SES and TB rates were calculated for foreign-born and U.S.-born populations in each quartile.

RESULTS

TB rates were highest in the quartiles with low SES for both U.S.-born and foreign-born populations. However, while TB rates increased five-fold or more from the two highest to the two lowest SES quartiles among the U.S.-born, they increased only by a factor of 1.3 among the foreign-born.

CONCLUSIONS

Low SES is only weakly associated with TB among foreign-born persons in the United States. The traditional associations of TB with poverty are not sufficient to explain the epidemiology of TB among foreign-born persons in this country and perhaps in other developed countries. TB outreach and research efforts that focus only on low SES will miss an important segment of the foreign-born population.

Estimating the burden of tuberculosis among foreign-born persons acquired prior to entering the U.S., 2005-2009

BACKGROUND

The true burden of reactivation of remote latent tuberculosis infection (reactivation TB) among foreign-born persons with tuberculosis (TB) within the United States is not known. Our study objectives were to estimate the proportion of foreign-born persons with TB due reactivation TB and to describe characteristics of foreign-born persons with reactivation TB.

METHODS

We conducted a cross-sectional study of patients with an M. tuberculosis isolate genotyped by the U.S. National TB Genotyping Service, 2005-2009. TB cases were attributed to reactivation TB if they were not a member of a localized cluster of cases. Localized clusters were determined by a spatial scan statistic of cases with isolates with matching TB genotype results. Crude odds ratios and 95% confidence intervals were used to assess relations between reactivation TB and select factors among foreign-born persons.

MAIN RESULTS

Among the 36,860 cases with genotyping and surveillance data reported, 22,151 (60%) were foreign-born. Among foreign-born persons with TB, 18,540 (83.7%) were attributed to reactivation TB. Reactivation TB among foreign-born persons was associated with increasing age at arrival, incidence of TB in the country of origin, and decreased time in the U.S. at the time of TB diagnosis.

CONCLUSIONS

Four out of five TB cases among foreign-born persons can be attributed to reactivation TB and present the largest challenge to TB elimination in the U.S. TB control strategies among foreign-born persons should focus on finding and treating latent tuberculosis infection prior to or shortly after arrival to the United States and on reducing the burden of LTBI through improvements in global TB control.

Impact of immigration on the molecular epidemiology of tuberculosis in Rhode Island

While foreign-born persons constitute only 11% of the population in the state of Rhode Island, they account for more than 65% of incident tuberculosis (TB) annually. We investigated the molecular-epidemiological differences between foreign-born and U.S.-born TB patients to estimate the degree of recent transmission and identify predictors of clustering. A total of 288 isolates collected from culture-confirmed TB cases in Rhode Island between 1995 and 2004 were fingerprinted by spoligotyping and 12-locus mycobacterial interspersed repetitive units. Of the 288 fingerprinted isolates, 109 (37.8%) belonged to 36 genetic clusters. Our findings demonstrate that U.S.-born patients, Hispanics, Asian/Pacific islanders, and uninsured patients were significantly more likely to be clustered. Recent transmission among the foreign-born population was restricted and occurred mostly locally, within populations originating from the same region. Nevertheless, TB transmission between the foreign-born and U.S.-born population should not be neglected, since 80% of the mixed clusters of foreign- and U.S.-born persons arose from a foreign-born source case. We conclude that timely access to routine screening and treatment for latent TB infection for immigrants is vital for disease elimination in Rhode Island.

[Molecular epidemiology of tuberculosis in Almeria (Spain). Factors associated with recent transmission]

BACKGROUND

Molecular epidemiology is used in tuberculosis (TB) to identify clusters in which the cases are assumed to belong to the same recent transmission chain. An endogenous reactivation of latent TB is considered when the Mycobacterium tuberculosis isolates have a unique genotype.

OBJECTIVE

To describe factors associated with recent transmission of TB in Almeria, from 2003-2007.

METHODS

We conducted an observational prospective study that included patients with Mycobacterium tuberculosis positive culture. The strains were genotyped by Restriction Fragment Length Polymorphism and spoligotyping. Adjusted odds ratio and 95% confidence intervals were calculated to study factors associated with cluster groups, using a multivariate logistic regression model.

RESULTS

We analysed 427 isolates, of which 71% were from males and 56.2% of them belonged to foreign residents. Furthermore, 44% were classified as a cluster. The resistance to isoniazid was 8.4%. The factors associated with clusters were age, principally the group under 10 years (adjusted OR=12.75; 95% CI, 2.52-64.58) and the group aged between 50-59 years (adjusted OR=13.85; 95% CI, 3.04-63.17), and born in Spain (adjusted OR=2.17; 95% CI, 1.41-3.36).

CONCLUSIONS

In Almeria, native population, children under 10 years old and patients aged between 50-59 years have more probability to belong to the same recent transmission chain. The molecular epidemiology can be used to find out which population groups need more control and this information must be used in tuberculosis prevention programs.

Revisiting rates of reactivation tuberculosis: a population-based approach

RATIONALE

Reactivation tuberculosis (TB) occurs as a result of reactivation of latent TB infection (LTBI), and was reported to occur in the United States at a rate of 0.10 to 0.16 cases per 100 person-years in the 1950s; it has not been measured since.

OBJECTIVES

To calculate the rate of reactivation TB in a U.S. community.

METHODS

A population-based tuberculin skin test survey for LTBI was performed in western Palm Beach County, Florida, from 1998 to 2000 along with a cluster analysis of TB case isolates in the same area from 1997 to 2001. Reactivation (unclustered) TB was presumed to have arisen from the population with LTBI.

MEASUREMENTS AND MAIN RESULTS

The rate of reactivation TB among persons with LTBI without HIV infection was 0.040 cases per 100 person-years (95% confidence interval [CI], 0.024-0.067) using the n method and 0.058 cases per 100 person-years (95% CI, 0.038-0.089) using the n-1 method. HIV infection was the strongest risk factor for reactivation (rate ratio [RR], 57; 95% CI, 27-120; P < 0.001). Among persons without HIV infection, reactivation was increased among those older than 50 years (RR, 3.8; 95% CI, 1.3-11) and among those born in the United States (RR, 3.2; 95% CI, 1.1-9.3).

CONCLUSIONS

Rates of reactivation TB in this area have declined substantially since the 1950s. The greatest part of this decline may be attributed to the disappearance of old, healed TB in the population. If similar declines are seen in other areas of the United States, the cost-effectiveness of screening and treatment of LTBI may be substantially less than previously estimated.

Transmission permeability of tuberculosis involving immigrants, revealed by a multicentre analysis of clusters

In recent years, the number of cases of tuberculosis (TB) among immigrants in Spain has increased markedly, and led to this analysis of the recent transmission patterns of TB in the immigrant population in Madrid. The countries from which the highest number of immigrant cases have been reported were Ecuador (21%), Romania (16%), Morocco (12%), Peru (11%) and Bolivia (9%). Fifty-one per cent of the cases were from South America. In a multicentre study (2004-2006), IS6110 restriction fragment length polymorphism and spoligotyping were used to genotype the Mycobacterium tuberculosis isolates from 632 immigrant cases from 47 countries. A total of 183 cases (29%) were grouped into 59 clusters, which are markers of potential transmission events. Most of the clusters (81%) included patients living in different healthcare districts, and 54% of the clusters were multinational. When a sample of 478 autochthonous cases was included, 53% of the clusters involving immigrants also included autochthonous cases. This study revealed marked transmission permeability among nationalities and between the immigrant and the autochthonous populations.

Transmission classification model to determine place and time of infection of tuberculosis cases in an urban area

We conducted a population-based study in the Rotterdam region of The Netherlands to determine the place and time of infection of tuberculosis (TB) cases using conventional epidemiological and genotyping information. In particular, we focused on the extent of misclassification if genotyping was not combined with epidemiological information. Cases were divided into those with a unique mycobacterial DNA fingerprint, a clustering fingerprint, and an unknown fingerprint. We developed transmission classification trees for each category to determine whether patients were infected in a foreign country or recently (<or=2 years) or remotely (>2 years) infected in The Netherlands. Of all TB cases during the 12-year study period, 38% were infected in a foreign country, 36% resulted from recent transmission in The Netherlands, and 18% resulted from remote infection in The Netherlands, while in the remaining cases (9%) either the time or place of infection could not be determined. The conventional epidemiological data suggested that at least 29% of clustered cases were not part of recent chains of transmission. Cases with unknown fingerprints, almost all culture negative, relatively frequently had confirmed epidemiological links with a recent pulmonary TB case in The Netherlands and were more often identified by contact tracing. Our findings highlight the idea that genotyping should be combined with conventional epidemiological investigation to establish the place and time of infection of TB cases as accurately as possible. A standardized way of classifying TB into recently, remotely, and foreign-acquired disease provides indicators for surveillance and TB control program performance that can be used to decide on interventions and allocation of resources.

Advanced survey of tuberculosis transmission in a complex socioepidemiologic scenario with a high proportion of cases in immigrants

BACKGROUND

An increase in the incidence of tuberculosis (TB) in immigrants has changed the socioepidemiologic scenario in Spain. It is generally assumed that TB in immigrants is the result of importation of infection, but the role of recent transmission is rarely considered. Standard contact tracing is not suitable for the survey of transmission in this complex scenario.

METHODS

During the study period (2003-2006), we genotyped 356 (90.4%) of 394 isolates from patients with microbiologically confirmed TB in Almería, the province with the highest percentage of TB cases among immigrants in Spain. The epidemiologic survey of TB transmission was performed by active data collection using standardized interviews of the patients with TB and subsequent interviews of the clustered patients (who were clustered on the basis of the restriction fragment-length polymorphism types of their isolates) to identify transmission locations (supported by nominal and/or photographic recognition by the clustered patients).

RESULTS

Of all 356 genotyped isolates, 131 (36.8%) were clustered, suggesting recent transmission. The difference between the clustering rate for immigrants (32.8%) and that for native patients (41.6%) was not statistically significant (P = .087); of the 45 clusters, 15 (33.3%) involved only immigrants, 17 (37.8%) involved only autochthonous patients, and 13 (28.9%) involved both immigrants and autochthonous patients. The advanced system to investigate the clustered patients succeeded in detecting links in 10 of the 12 clusters that involved >4 patients, whereas the conventional approach, based on contact tracing, could detect links in only 2 clusters.

CONCLUSIONS

Recent transmission among immigrants and transmission permeability between the immigrant and autochthonous populations were found. Epidemiologic strategies that combine universal genotyping and refined surveys of the clustered patients are needed to investigate transmission patterns in complex scenarios.

Risk of Progression to Active Tuberculosis Among Foreign-Born Persons With Latent Tuberculosis

BACKGROUND

Increased risk for tuberculosis (TB) disease has been identified in foreign-born persons in the United States, particularly during the first 5 years after their arrival in the United States. This could be explained by undetected TB disease at entry, increased prevalence of latent TB infection (LTBI), increased progression from LTBI to TB, or a combination of these factors.

METHODS

We performed a cluster analysis of TB cases in Boston and a case-control study of risk factors for TB with an unclustered isolate among Boston residents with LTBI to determine whether such persons have an increased risk for reactivation of disease.

RESULTS

Of 321 case patients with TB seen between 1996 and 2000, 133 isolates were clustered and 188 were not. In multivariate analysis, foreign birth was associated with an unclustered isolate (odds ratio [OR], 2.2; 95% confidence interval [CI], 1.2 to 3.8; p < 0.01), while being a close contact of a TB case was negatively associated (OR, 0.22; 95% CI, 0.07 to 0.73; p = 0.02). When 188 TB patients with unclustered isolates were compared to 188 age-matched control subjects with LTBI, there was no association between the occurrence of TB and foreign birth (OR, 0.71; 95% CI, 0.42 to 1.3); among foreign-born persons, there was no association between the occurrence of TB and being in the United States <or= 5 years (OR, 0.90; 95% CI, 0.56 to 1.44).

CONCLUSIONS

We conclude that the increased risk for TB among foreign-born persons in the United States may be attributable to the increased prevalence of LTBI among foreign-born persons or the increased prevalence of active disease at arrival in the United States, but not to an increased rate of reactivation among persons with LTBI.

Analysis of changes in recent tuberculosis transmission patterns after a sharp increase in immigration

We conducted a population-based molecular epidemiological study of tuberculosis (TB) in Madrid, Spain (2002 to 2004), to define transmission patterns and factors associated with clustering. We particularly focused on examining how the increase in TB cases among immigrants in recent years (2.8% in 1997 to 1999 to 36.2% during the current study) was modifying transmission patterns. Mycobacterium tuberculosis isolates obtained from patients living in nine districts of Madrid (1,459,232 inhabitants) were genotyped. The TB case rate among foreign-born people was three to four times that of Spanish-born people, and the median time from arrival to the onset of treatment was 22.4 months. During the study period, 227 (36.3%) patients were grouped in 64 clusters, and 115 (50.7%) of them were in 21 clusters with mixed Spanish-born and foreign-born patients. Three of the 21 mixed clusters accounted for 21.1% of clustered patients. Twenty-two of 38 (57.9%) immigrants in mixed clusters were infected with TB strains that had already been identified in the native population in 1997 to 1999, including the three most prevalent strains. Factors identified as independent predictors of clustering were homelessness (odds ratio [OR], 2.3; 95% confidence interval [95% CI], 1.2 to 4.5; P = 0.011) and to be born in Spain (OR, 1.8; 95% CI, 1.2 to 2.6; P = 0.002). The results indicated that (i) TB transmission was higher in Spanish-born people, associated mainly with homelessness, (ii) that foreign-born people were much less likely to be clustered, suggesting a higher percentage of infection before arriving in Spain, and (iii) that an extensive transmission between Spanish- and foreign-born populations, caused mainly by autochthonous strains, was taking place in Madrid.

Identifying Mycobacterium tuberculosis complex strain families using spoligotypes

We present a novel approach for analysis of Mycobacterium tuberculosis complex (MTC) strain genotyping data. Our work presents a first step in an ongoing project dedicated to the development of decision support tools for tuberculosis (TB) epidemiologists exploiting both genotyping and epidemiological data. We focus on spacer oligonucleotide typing (spoligotyping), a genotyping method based on analysis of a direct repeat (DR) locus. We use mixture models to identify strain families of MTC based on their spoligotyping patterns. Our algorithm, SPOTCLUST, incorporates biological information on spoligotype evolution, without attempting to derive the full phylogeny of MTC. We applied our algorithm to 535 different spoligotype patterns identified among 7166 MTC strains isolated between 1996 and 2004 from New York State TB patients. Two models were employed and validated: a 36-component model based on global spoligotype database SpolDB3, and a randomly initialized model (RIM) containing 48 components. Our analysis both confirmed previously expert-defined families of MTC strains and suggested certain new families. SPOTCLUST, which is available online, can be further improved by incorporating data obtained using additional strain genetic markers and epidemiological information. We demonstrate on New York City (NYC) patient data how the resulting models can potentially form the basis of TB control tools using genotyping.

American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America: Controlling Tuberculosis in the United States

During 1993-2003, incidence of tuberculosis (TB) in the United States decreased 44% and is now occurring at a historic low level (14,874 cases in 2003). The Advisory Council for the Elimination of Tuberculosis has called for a renewed commitment to eliminating TB in the United States, and the Institute of Medicine has published a detailed plan for achieving that goal. In this statement, the American Thoracic Society (ATS), Centers for Disease Control and Prevention (CDC), and the Infectious Diseases Society of America (IDSA) propose recommendations to improve the control and prevention of TB in the United States and to progress toward its elimination. This statement is one in a series issued periodically by the sponsoring organizations to guide the diagnosis, treatment, control, and prevention of TB. This statement supersedes the previous statement by ATS and CDC, which was also supported by IDSA and the American Academy of Pediatrics (AAP). This statement was drafted, after an evidence-based review of the subject, by a panel of representatives of the three sponsoring organizations. AAP, the National Tuberculosis Controllers Association, and the Canadian Thoracic Society were also represented on the panel. This statement integrates recent scientific advances with current epidemiologic data, other recent guidelines from this series, and other sources into a coherent and practical approach to the control of TB in the United States. Although drafted to apply to TB-control activities in the United States, this statement might be of use in other countries in which persons with TB generally have access to medical and public health services and resources necessary to make a precise diagnosis of the disease; achieve curative medical treatment; and otherwise provide substantial science-based protection of the population against TB. This statement is aimed at all persons who advocate, plan, and work at controlling and preventing TB in the United States, including persons who formulate public health policy and make decisions about allocation of resources for disease control and health maintenance and directors and staff members of state, county, and local public health agencies throughout the United States charged with control of TB. The audience also includes the full range of medical practitioners, organizations, and institutions involved in the health care of persons in the United States who are at risk for TB.

The transmission of tuberculosis in the light of new molecular biological approaches

This review briefly summarises the recent achievements in tuberculosis epidemiology associated with the introduction of molecular methods, and considers the implications of these methods for the understanding of occupational tuberculosis transmission. Special attention is paid to the relative contribution of recently transmitted tuberculosis; risk factors for recent transmission; and the occurrence and frequency of exogenous reinfection. There is a need for occupational epidemiological studies, which should combine the methods of "classical" epidemiology with those of molecular epidemiology.

Impact of genotyping of Mycobacterium tuberculosis on public health practice in Massachusetts

Massachusetts was one of seven sentinel surveillance sites in the National Tuberculosis Genotyping and Surveillance Network. From 1996 through 2000, isolates from new patients with tuberculosis (TB) underwent genotyping. We describe the impact that genotyping had on public health practice in Massachusetts and some limitations of the technique. Through genotyping, we explored the dynamics of TB outbreaks, investigated laboratory cross-contamination, and identified Mycobacterium tuberculosis strains, transmission sites, and accurate epidemiologic links. Genotyping should be used with epidemiologic follow-up to identify how resources can best be allocated to investigate genotypic findings.

DNA fngerprinting of Mycobacterium tuberculosis: lessons learned and implications for the future

DNA fingerprinting of Mycobacterium tuberculosis--a relatively new laboratory technique--offers promise as a powerful aid in the prevention and control of tuberculosis (TB). Established in 1996 by the Centers for Disease Control and Prevention (CDC), the National Tuberculosis Genotyping and Surveillance Network was a 5-year prospective, population-based study of DNA fingerprinting conducted from 1996 to 2000. The data from this study suggest multiple molecular epidemiologic and program management uses for DNA fingerprinting in TB public health practice. From these data, we also gain a clearer understanding of the overall diversity of M. tuberculosis strains as well as the presence of endemic strains in the United States. We summarize the key findings and the impact that DNA fingerprinting may have on future approaches to TB control. Although challenges and limitations to the use of DNA fingerprinting exist, the widespread implementation of the technique into routine TB prevention and control practices appears scientifically justified.