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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
Apparent Genotyping Cluster Among Recent Immigrants from the Philippines:
IS6110-based RFLP Needed to Discriminate Between Isolates
Belonging to the Manila Strain
Previous results from the National Tuberculosis Genotyping and
Surveillance Network and other studies showed that spoligotyping
alone was not particularly helpful in distinguishing between isolates
that belonged to a group generally referred to as the Beijing family
of M. tuberculosis isolates. Data from CDC suggest that MIRU
analysis, especially when combined with RFLP analysis, will be more
discriminatory than spoligotyping alone. At the same time, we are
beginning to see new genotyping families that contain isolates that
are often not distinguished by spoligotyping plus MIRU analysis.
The following case study describes patients with isolates from one
such family, which has been named the Manila strain family because
of its predominance in patients from Manila.
During 2000--2003, isolates from seven patients were identified
as belonging to the same PCR cluster (i.e., each isolate had the
same spoligotype and MIRU type). On the basis of the spoligotype
and MIRU type, the CDC recognized that these isolates belonged to
the Manila family. Analysis of data from the initial case-patient
interviews revealed that they were all recent immigrants from the
Philippines, but they lived in different regions of Wisconsin. The
contact investigations of the cases did not reveal epidemiologic
links between any of the patients.
Because no epidemiologic links were identified for these PCR-clustered
cases, the TB program requested that the seven isolates be analyzed
by RFLP, which revealed seven distinct patterns. Therefore, despite
identical spoligotypes and MIRU types, these seven isolates were
shown to be genetically distinct by RFLP analysis. The TB program
did not undertake a cluster investigation, since the seven isolates
were shown not to belong to the same genotyping cluster.
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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