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Guide to the Application of Genotyping to Tuberculosis Prevention and Control										Related Pages
										**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).**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).
							
					
						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
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