Introduction to Tuberculosis Genotyping 

National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention

Division of Tuberculosis Elimination

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Objectives

At the end of the presentation, participants will be 

able to 

Explain the basics of tuberculosis (TB) genotyping

Describe how TB genotyping can be useful in TB control

Explain how genotyping results are obtained

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QUESTION:What is TB Genotyping?

Laboratory method to detect TB infection

A blood test to detect drug-resistant TB

Laboratory approach to analyze genetic material (DNA) of Mycobacterium tuberculosis (M. tuberculosis)

Tool to help understand transmission of M. tuberculosis

Both c and d

  DNA = deoxyribonucleic acid

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ANSWER:TB Genotyping Is

Laboratory method to detect TB infection

A blood test to detect drug-resistant TB

Laboratory approach to analyze genetic material (DNA) of M. tuberculosis

Tool to help understand transmission of M. tuberculosis

Both c and d

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  DNA = deoxyribonucleic acid

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TB Genotyping

Only for culture-confirmed TB

The technique requires material from a culture

Matching genotypes may indicate that TB cases are related

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Genotypes and M. tuberculosis Transmission

Genotyping helps us understand transmission relationships between TB cases

We expect genotypes from transmission-related TB cases to match

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Matching Game –Do the Pictures Match?

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Unauthorized use of these images is prohibited.

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Genotype Clusters

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How Can Genotyping be Useful in TB Control? (1)

Assist with contact investigations

Confirm or refute patient connections

Find previously unidentified contacts

Detect and prevent outbreaks

Refute outbreaks

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Distinguish relapse from new infection

Detect false-positive culture results

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How Can Genotyping be Useful in TB Control? (2)

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Case Scenario 1: A Household (1)

Persons diagnosed with TB spent most of their time together at the same house

Likely related by transmission

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| Mother   | Genotype 1 |
|----------|------------|
| Son      | Genotype 1 |
| Neighbor | Genotype 1 |

Case Scenario 1: A Household (2)

Genotype results for TB cases linked to household:

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All cases had matching genotypes

All spent time together in the same house

These cases were likely transmission-related 

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Case Scenario 1: A Household (3)

Interpretation of Genotyping Results

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Contact investigation did not find any other cases

Two other family members were diagnosed and treated for TB infection

Neighbor with TB did not identify any other contacts aside from this family

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Case Scenario 1: A Household (4)

Back to the Household

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| Mother    | Genotype 1 |
|-----------|------------|
| Son       | Genotype 1 |
| Neighbor  | Genotype 1 |
| Patient A | Genotype 1 |
| Patient B | Genotype 1 |

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Case scenario 1: A Household (5)

Review of Genotype Data for County A – 2013 

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Five cases with matching genotypes within 6 months

Cases may all be related by transmission, but

When?

Where?

More information is needed

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Case Scenario 1: A Household (6)

What do the Genotype Results Indicate?

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Investigate to understand relationship of Patient A and Patient B to the other patients in the cluster

Identify likely locations of transmission

Determine if there are missed contacts

Review

Public health records

Contact investigation logs

Estimated infectious periods

Re-interview TB patients and contacts

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Case Scenario 1: A Household (7)

Next Steps

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Case Scenario 2: A Workplace (1)

Within one month

Three women diagnosed with TB

All work at the same casino

All work on the same evening shift

One woman’s boyfriend also diagnosed with TB

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Case Scenario 2: A Workplace (2)QUESTION: Are these TB cases related by transmission?

Yes

No

Maybe

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Yes

No

Maybe!

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Case Scenario 2: A Workplace (3)ANSWER: Are these TB cases related by transmission?

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| Employee 1 | Genotype 2 |
|------------|------------|
| Employee 2 | Genotype 3 |
| Employee 3 | Genotype 4 |
| Boyfriend  | Genotype 5 |

Case Scenario 2: A Workplace (4) Genotype Results for TB Cases Linked to Casino 

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Case Scenario 2: A Workplace (5) QUESTION: How to interpret the genotype results?

The genotype data are wrong

The genotype data could be wrong, since cases are linked epidemiologically

These cases are not related by transmission

I don’t know

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The genotype data are wrong

The genotype data could be wrong, since cases are linked epidemiologically

These cases are not related by transmission

I don’t know

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Case Scenario 2: A Workplace (6) ANSWER: How to interpret the genotype results?

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Case Scenario 2: A Workplace (7) Interpretation of Genotype Results

Genotype results from all cases were different

These cases are not related by transmission

This was a coincidence

Four contact investigations are needed

Three in same work site

Not an outbreak

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How are Genotyping Results Obtained?

Specimen

TB isolated 

from culture

TB genotype test result

Person with suspected TB

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Take Home Points

TB genotyping can be useful in TB control

Find additional contacts

Detect and prevent outbreaks

Refute outbreaks

Interpreting genotyping results can be as simple as, “Do the pictures match?”

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Unauthorized use of this image is prohibited.

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CDC Resources on Genotyping

CDC TB genotyping website

www.cdc.gov/tb/programs/genotyping/default.htm

TB genotyping best practices

www.cdc.gov/tb/publications/factsheets/statistics/Genotyping_BestPractices.pdf

TB Genotyping Information Management System (TB GIMS) 

https://ajtv-nifm-web2.cdc.gov/TBGIMS/

Email CDC

tbgenotyping@cdc.gov

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For more information please contact the Centers for Disease Control and Prevention

1600 Clifton Road NE, Atlanta,  GA  30329

Telephone: 1-800-CDC-INFO (232-4636)/TTY: 1-888-232-6348

Web:  http://www.cdc.gov

Or  TBGenotyping@cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

Division of Tuberculosis Elimination

Thank you!

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