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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
Investigation of a Multistate Tuberculosis Outbreak: The
Importance of Comparing Genotype Results Between Adjacent TB Programs
From June 1998 through June 1999, 15 young African-Americans from
Baltimore, Maryland and New York City developed TB with isolates
that had a matching RFLP pattern (McElroy 2002). All but one of
the patients were members of the transgender community and belonged
to a social organization that regularly met to dance and participate
in dressing competitions known as “balls.”
Since members of this social organization traveled widely, health
officials were concerned that transmission of this outbreak strain
could be occurring in other cities. To search for additional patients
whose isolates might match the outbreak genotype, the investigators
took advantage of the National Tuberculosis Genotyping and Surveillance
Network database, which contains over 6,000 unique RFLP images.
This search revealed four previously unrecognized matches—three
were found to be close contacts of a transgender person who was
involved in the outbreak (one lived in the same house, one worked
at the same location, and the third worked as a custodian on the
same floor as the patient). The fourth patient with a matching genotype,
a 42-year-old man, died before he could be interviewed.
Additional isolates for genotyping were obtained from laboratories
in New York City, Atlanta, and Philadelphia by searching existing
TB records for patients that fit the outbreak profile. This search
came up with eight additional patients, all from New York City,
with isolates matching the outbreak strain. Interviews revealed
that all but one were part of the same transgender social group.
During the investigation, five additional patients who had epidemiologic
links to the original outbreak-associated patients, developed TB,
and the genotypes of their isolates matched the outbreak strain
(Figure 2.1). Another patient, a 7-year-old girl, developed clinical
TB but never had a positive culture result. Although no isolate
was available to prove that she was infected with the outbreak strain,
this is likely, since she became ill while living with her sister,
one of the outbreak patients. This outbreak investigation shows
the importance of being able to compare genotyping results between
adjacent TB programs.
![Epidemic curve of investigation of a multistate TB outbreak among transgender persons involving cases from New Jersey, Maryland, New York City, and Baltimore. A search of the National Tuberculosis Genotyping and Surveillance Network genotyping database led to the identification of four additional outbreak-related cases (McElroy 2002).](https://webarchive.library.unt.edu/eot2008/20090122072524im_/http://www.cdc.gov/tb/genotyping/images/Year_of_Diagnosis.gif)
Figure 2.1. Epidemic curve of investigation of a
multistate TB outbreak among transgender persons involving cases
from New Jersey, Maryland, New York City, and Baltimore. A search
of the National Tuberculosis Genotyping and Surveillance Network
genotyping database led to the identification of four additional
outbreak-related cases (McElroy 2002).
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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