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Guide to the Application of Genotyping to Tuberculosis Prevention
and Control
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Tuberculosis Genotyping Case Studies: How TB Programs
Have Used Genotyping
In this chapter, we will provide examples of how TB programs have
used genotyping to assist them in conducting important TB control
activities. Specifically, this chapter provides examples of how
genotyping results have helped identify new, previously unrecognized
transmission links between patients with TB, how they have been
used effectively during outbreak investigations, and how these results
can be used in the future to detect outbreaks at early stages. We
will also describe how genotyping has been used to monitor epidemiologic
trends, evaluate program performance, and identify instances of
false-positive cultures that can result from mislabeling clinical
specimens, cross-contamination of cultures, or other problems.
In the past, most programs have submitted only selected M. tuberculosis
isolates for genotyping. Although selective genotyping provides
new insights into TB transmission, the power of genotyping is increased
considerably when isolates from all patients with culture-positive
TB are genotyped, even before contact investigations or outbreak
investigations raise the suspicion that there might be a link between
patients. In reading the case studies that follow, pay attention
to what advantages accrue to programs that institute selective genotyping
and what advantages accrue only to programs that institute universal
genotyping.
Most of the data that has been gathered about the utility of TB
genotyping is based on the genotyping approach used by the TB programs
that participated in the National Tuberculosis Genotyping and Surveillance
Network (NTGSN) (Castro 2002). A special issue of the journal
Emerging Infectious Diseases was devoted to presenting the findings
of the NTGSN study and is available at
www.cdc.gov/ncidod/EID/vol8no11/contents_v8n11.htm.
The NTGSN study was based on IS6110-based RFLP analysis
supplemented by spoligotyping for certain isolates. Data are still
limited about how this past approach will compare with the current
approach used by the CDC Tuberculosis Genotyping Program, which
is based on spoligotyping and MIRU analysis of all isolates, with
IS6110-based RFLP for only selected isolates (see Chapter
5, Developing a Tuberculosis Genotyping Program, for
details about when RFLP is helpful). The first three of the following
examples were reported by TB programs that are using the current
approach; the others come from the National Tuberculosis Genotyping
and Surveillance Network.
Last Reviewed: 05/18/2008 Content Source: Division of Tuberculosis Elimination
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
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