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Guide to the Application of Genotyping to Tuberculosis Prevention and Control										Related Pages
										**CDC Tuberculosis Genotyping Laboratory Procedures**
**Science Behind TB Genotyping**
Genotyping is based on an analysis of DNA. Mycobacteria reproduce by binary fission, which means that in almost all cases each new bacillus has identical DNA, just as human identical twins are genetically identical to each other. However, changes in the DNA occur spontaneously at low frequency. Over time, these changes, known as DNA mutations, have accumulated to produce the diversity of *M. tuberculosis* strains currently circulating in the world.
The diversity of strains provides a means to identify instances of recent transmission of TB as well as the chains of transmission that occur among persons with TB. This diversity also helps to elucidate the patterns and dynamics of TB transmission. When a person with TB improves but then becomes ill again, this diversity can differentiate reactivation with the same strain of *M. tuberculosis* from reinfection with a different strain. Genotyping can also be used to identify false-positive cultures.
Advances in DNA analytic methods have made it possible for TB programs to obtain rapid and reliable genotyping results. These advances include
the determination of the complete DNA sequence of *M. tuberculosis* in 1998;
the development of IS*6110*-based RFLP genotyping, which provided a discriminatory typing method and led to a standardized system for genotyping *M. tuberculosis* isolates; and
the development of two new methods, spoligotyping and MIRU analysis, which are based on PCR and provide much more rapid results than RFLP analysis.
							
					
						Page last reviewed:  September 1, 2012					Content source: 	Division of Tuberculosis Elimination, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention homeGuide to the Application of Genotyping to Tuberculosis Prevention and Control
Acknowledgments
Introduction to Tuberculosis Genotypingplus icon
Introduction to this Guide
Overview of Tuberculosis Genotyping
Overview of the CDC Tuberculosis Genotyping Program
TB Program Eligibility and Application Procedures
Tuberculosis Genotyping Case Studiesplus icon
Investigation of a Genotyping Cluster in a Low-Incidence State
Apparent Genotyping Cluster among Recent Immigrants from the Philippines
False-Positive Culture Investigation
Algorithm to Detect False-Positive Cultures
A Misdiagnosis that was Identified with Genotyping
Genotyping Used to Improve Contact and Cluster Investigations
Identification of Nontraditional Transmission Settings
Investigation of a Multistate Tuberculosis Outbreak
Homeless Shelter Outbreak Investigation
Using Genotyping to Evaluate the Impact of a Screening Program
CDC Tuberculosis Genotyping Laboratory Proceduresplus icon
Science behind Tuberculosis Genotyping
Description of Genotyping Methods
Submission of Isolates
Genotyping Results, Designation of Clusters, and Reporting
Suspected False-Positive Cultures
IS*6110*-based RFLP Analysis
Combining Genotyping and Epidemiologic Data to Improve Our Understanding of TB Transmissionplus icon
Definitions
Reading the Genotyping Laboratory Report
Comparing Genotyping and Epidemiologic Results from Two TB Patients
Comparing Genotyping and Epidemiologic Results from Three or More TB Patients
Clustering as a Surrogate Measure of Recent Transmission
Developing a Tuberculosis Genotyping Programplus icon
Developing a Written Plan
Initial Decisions
Establishing Procedures for:plus icon
Submitting Isolates
Receiving and Acting on Genotyping Results
Requesting RFLP Analysis
Submitting Additional Isolates from the Same Patient
Comparing Genotyping Results between Jurisdictions
False-Positive Cultures
Database Management and Quality Control
Special Issues
Applying Genotyping Results to Tuberculosis Control Practicesplus icon
Evaluating Matching Genotypes
Evaluating Nonmatching Genotypes
Suspected False-Positive Culture Investigations
Expanded Contact Investigations
Outbreak Investigations
Cluster Investigations
Monitoring Trends
Appendicesplus icon
Appendix A: Glossary and Abbreviations
Appendix B: References and Useful Resourcesplus icon
References Cited in the Guide
NTGSN Special Issue References
Information on Packaging and Shipping Infectious Substances
Core Steps of an Outbreak Investigation
Consultants Available to Offer Guidance To receive email updates about this page, enter your email address: Email Address			What's this?				Submit


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