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U.S. Department of Health and Human Services

  

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TB Notes 1, 2002

Updates From the Surveillance and Epidemiology Branch

TB Epidemiologic Studies Consortium

The first meeting of the new TB Epidemiologic Studies consortium (TBESC) was held December 5-7 in Atlanta, Georgia. This meeting was critical for setting the consortium in motion. The primary purpose of the TBESC is to design and carry out epidemiologic, behavioral, economic, laboratory, and operational research to evaluate interventions to prevent TB. The TBESC consists of 22 collaborating sites. The ability to combine the work of researchers with different areas of expertise and focus on specific problems will give the TBESC a unique ability to have an important impact. With the task of developing a research agenda, the TBESC will not be working in a vacuum. Rather, it has clear guidance from the Institute of Medicine report which provides a framework to use in developing the research agenda. The TBESC is modeled as an investigator-driven collaboration of peer intellectual contribution. The idea is that researchers and TB controllers can do more together than individually. We hope that the partnerships created by TBESC will make for more successful science.

The TBESC consists of a formal partnership between academic centers and TB control programs. This partnership is distinct from other federally funded activities, such as the relationship that NIH has with academic centers or that DTBE has with TB control programs through its cooperative agreements. We hope this mixture will help the TBESC conduct the highest quality research with strong programmatic relevance. DTBE has been working to bring this concept to fruition for over 2 years. The founding principal has been to develop a group of experts who can be involved in all the activities related to advancing TB control:

  • debating a research agenda
  • designing and conducting research studies
  • publishing the scientific findings
  • implementing the research results
  • measuring the impact

The TBESC was modeled after the TB Trials Consortium (TBTC). However, the scientific focus of the TBTC is on clinical trials, while the TBESC's activities will be more diverse. In addition, the TBTC started from a single study and grew into a smoothly functioning consortium; the TBESC started out as a consortium and is now developing the ground rules that will be used to guide its activities. The TBESC will be managed through a contractual relationship between CDC and consortium members.

— Reported by Scott J.N. McNabb, PhD, MS
Division of TB Elimination


The Importance of DNA Fingerprinting in TB Control Efforts

The following was adapted from an article presented at the meeting of the National TB Controllers Association in June 2001.

Overview
DNA fingerprinting has been used successfully in conjunction with traditional laboratory and epidemiologic methods to differentiate M. tuberculosis strains, to help identify new TB case-patients, and to confirm suspected laboratory contamination events. The restriction fragment length polymorphism (RFLP) technique, which is based on a repeating genetic element called insertion sequence 6110 (IS6110), is detectable only in species of the M. tuberculosis complex. This genetic element occurs in varying numbers of copies and in different positions on the chromosome, and thus results in a unique genotype, or fingerprint, that is useful for characterizing the strain of M. tuberculosis that has infected a particular individual. Though RFLP has limitations (e.g., high cost, length of time required to culture the organism, and specialized training and laboratory equipment needed), it has been used with success to characterize M. tuberculosis strains worldwide and to help in public health follow-up.

Application of Genotyping to TB Control Efforts
Genotyping technology has been used effectively in outbreak investigations and in the identification of TB cases falsely reported as positive owing to laboratory cross-contamination. Genotyping can be used to augment traditional contact investigations and to further our understanding of risk factors and transmission patterns by identifying new contacts who would not be detected by routine contact investigations alone; these data could also be used to identify TB disease attributable to relapse (versus recent infection). In addition, DNA fingerprinting can be used as a surveillance tool to assess the effectiveness of TB control programs by examining strain variation throughout a geographic area over time. For example, if TB control efforts were effective, one would predict that the strains of M. tuberculosis in circulation in the area would not be genetically similar. This will be particularly useful in areas with current low incidences as we come closer to eliminating TB in the United States.

Incorporating Genotyping into TB Control Efforts in the US
The incorporation of genotyping methodology into routine TB control efforts represents a challenge. Although these techniques may continue to evolve, those currently in use have shown their utility as effective tools for both epidemiologic and program management purposes. An educational campaign should be initiated to disseminate information regarding current genotyping methodology to TB controllers and public health workers, so that they may better interpret and use these data in routine TB control efforts. To this end, CDC is now providing technical assistance in the development of a hands-on manual for TB controllers.

Genotyping Network Update
The National Tuberculosis Genotyping and Surveillance Network (NTGSN) was established in 1996 as a 5-year project involving seven regional genotyping laboratories and sentinel surveillance sites in the United States. M. tuberculosis isolates from the TB patients at each sentinel site were genotyped using one or more molecular technologies. Routine surveillance data were collected for each culture-positive case-patient. In addition, follow-up interviews were conducted for case-patients that had M. tuberculosis isolates that were genetically identical to isolates of other patients in the surveillance area. The project period is now at an end, and findings from the project will be presented later this year in a special issue of the CDC journal Emerging Infectious Diseases.

Reported by Scott McNabb, PhD, MS
Division of TB Elimination

 


Released October 2008
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