Guide to the Application of Genotyping to Tuberculosis Prevention
Combining Genotyping and Epidemiologic
Data to Improve Our Understanding of
Comparing Genotyping Results from Three or More TB Patients
In the previous discussion, we focused on possible transmission
between just two TB patients. When a genotyping cluster grows to
include three or more patients, additional information becomes available
that can shed light on how the patientsí cases might be related.
As additional TB patients are diagnosed and found to belong to
a previously identified genotyping cluster, more information about
possible epidemiologic links becomes available. The greater the
number of leads an investigator has to follow-up, the greater the
chance of identifying a shared link among patients in a cluster.
Data on additional patients is also helpful in identifying endemic
strains that are often found in the absence of evidence of recent
transmission. When a TB program first initiates a genotyping program,
it will be difficult to identify endemic strains until data from
many patients are gathered and analyzed. After several years, a
TB program will be able to identify M. tuberculosis strains
that are commonly detected in their area but are rarely associated
with patients who share known epidemiologic links.