Laboratory Diagnosis for MDR TB

Transcription

1 Laboratory Diagnosis for MDR TB Neha Shah MD MPH Centers for Disease Control and Prevention Division of Tuberculosis Elimination California Department of Public Health Guam March 07

2 Objectives Describe laboratory methods used for the detection, identification, genotyping, and drug susceptibility testing of M. tuberculosis.

3 Acknowledgements Slides unabashedly borrowed from Pennan Barry and Ed Desmond Tables blatantly cut/pasted from Curry MDR Survival Guide Google images Real people Family Pennan Barry Ed Desmond Jennifer Flood CA MDR Consult Service Jennifer Flood Lisa True Gayle Shack Leslie Henry Gisela Schecter Kristen Wendorf Pennan Barry 3

4 Who should you test? 4

5 MDR TB California, Country/Region No. % Former Soviet Republics 8 4. Laos 4.3 Korea, North and South 4. Burma 3.4 India 0.6 Central America 9. Peru.0 Ethiopia.9 Vietnam 7.9 Philippines.6 Kampuchea.4 China (incl Taiwan) 7. Mexico United States 8 0.

6 Increased Risk for MDR-TB History of previous TB treatment, particularly if recent Poor response to standard 4-drug treatment Culture remains (+) after months treatment Known exposure to MDR-TB case HIV (+) Higher incidence of Rifampin mono resistance

7 Other indications for resistance testing Increased stakes of drug resistance Laboratory issues. Case with large numbers of contacts (e.g., corrections, healthcare facilities, schools). Patients in whom unidentified drug resistance has increased risk, e.g., age < years, immunocompromised 3. Contacts with risks for rapid progression to active TB disease in whom effective preventive window treatment is needed (e.g., aged < years, or immunocompromised persons). Cultures mixed with other bacteria. Smear-positive but culture negative 7

8 What test to order? 8

9 Terminology Growth-based susceptibility tests = culture-based susceptibility tests = phenotypic susceptibility tests = DSTs Molecular tests for drug resistance Molecular susceptibility tests Genotypic susceptibility tests 9

10 Case 47 yo male from Nigeria History previously treated in Nigeria, symptomatic Date Smear Molecular Growth-based 0/3 + Xpert: RIF RES Low level INH RES RIF sensitive 0/3 + MDDR: rpob 3 = RES 0/3 + Lineprobe: No mutations Low-level INH RES RIF sensitive / + PSQ: rpob mutations (6 and 3) RIF RES Low-level INH RES 0

11 Growth-based susceptibility testing Reference standard for drug-susceptibility testing Differences in test method Differences in drug concentration Long turn around time

12 Benefits of Molecular Tests for Drug Resistance Reduced time to detection of resistance Time from empiric (first-line) treatment to MDR treatment 40 days less (median) Less transmission Less acquired resistance while DSTs pending Less ineffective LTBI treatment given to contacts Banerjee et al, J Clin Micro, 00

13 Molecular Tests 3

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16 Molecular Tests for Drug Resistance Non-sequencing (reports presence of a mutation) Molecular beacons: Cepheid Xpert MTB/Rif - - FDA authorized Line probes: Hain MTBDRplus and MTBDRsl, Innogenetics INNO-LiPA Rif.TB Laboratory developed tests

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18 Molecular Tests for Drug Resistance Sequencing (reports specific mutation) Pyrosequencing (PSQ) e.g., California, New York public health labs CDC s Molecular Detection of Drug Resistance (MDDR) Whole genome sequencing

19 Molecular Testing for Rifampin (rpob) Rifampin cornerstone of TB treatment Resistance requires a longer duration of therapy Rif resistance without INH resistance rare ~90% (4 of 9) Rif resistant cases MDR (California, 0-0) MDR Rif Mono-R 0% 0% 40% 60% 80% 00%

20 Xpert 0

21 Xpert Probes: Coverage of rpob Codo n #

22 Xpert Probes: Coverage of rpob Codo n # Most common resistance mutation (3 TTG) Location of missense mutation

23 Xpert Probes: Coverage of rpob Codo n # Most common silent mutation (4 TTT) Most common resistance mutation (3 TTG) Location of silent mutation Location of missense mutation

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27 Xpert Performance Rifampin Resistance Pooled median sensitivity: 9% (9% CrI: 90, 97) Pooled median specificity: 98% (9% CrI: 97, 99) Steingart 04 Cochrane Review ( Xpert-SR.pdf) 7

28 Sequencing-based testing 8

29 How Does Molecular Testing Work? Codons Amino Acids Mutations in single bases can lead to resistance

30 vce.bioninja.com.au Genetic Code

31 Types of mutations Silent Codon change No amino acid change Not associated with drug resistance Missense Codon change Amino acid change Some are associated with resistance 3

32 Drugs/Loci Antimicrobial agent Isoniazid (INH) INH and Ethionamide Gene/locus katg inha promoter Sensitivity Specificity (Sequencing) (Sequencing) Assays Hain, PSQ, MDDR INH ahpc promoter PSQ Rifampin (RIF) rpob Xpert, Hain, PSQ, MDDR Ethambutol (EMB) embb Hain, MDDR Pyrazinamide (PZA) pnca MDDR Fluoroquinolones gyra Hain, PSQ, MDDR Amikacin (AMK) rrs Hain, PSQ, MDDR Capreomycin (CAP) rrs tlya. 9.0 MDDR Lin, et al., Clin Lab Med. 04 Jun;34(): doi: 0.06/j.cll ; Lin, et al., J Clin Micro. 04;:47 3

33 Understanding sequence-based results 33

34 Approach to gyra If no mutations then LFX or MFX If mutation present: Request MFX MIC Use MFX mg but don t count it If MIC < 4 then continue MFX at high dose If MIC 4 then discontinue MFX IJTLD (3):47-40, 0 Poissy et al Antimicrob Agents and Chemo: Nov. 00,

35 Discordant Results 3

36 Why do I get different results? Drug Growth-based testing Molecular testing Ethambutol Frequent discordance 78.8 sensitive PZA Very hard to get culture correct to grow Numerous mutations Scattered everywhere Some resistant strains do not have mutations RIF Can be sensitive when mutation found Low-level resistance Silent mutations New mutations with unknown significance 36

37 Growth-based susceptibility testing

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39 Case 70 yo asymptomatic man from India with abnormal preimmigration CXR, no TB history Domestic CXR with multifocal infiltrates Sputum smear positive x 3 Xpert positive: rifampin resistant What do you do next? Start MDR treatment Pyrosequencing or MDDR Start RIPE Repeat Xpert on another specimen Start treatment for mono-rif resistance 39

40 Case Treatment held; PSQ available within days and clinically stable Pyrosequencing: katg mutation: INH R rpob 3TTG mutation = RIF R gyra (FQ): no mutations rrs (amikacin): no mutations What do you do next? Start MDR treatment Order MDDR Start RIPE Repeat Xpert on another specimen Order second line DSTs Cancel DSTs (already have molecular results) 40

41 Case 3 70 yo man from Mexico in US x years with 4 weeks of cough, no TB history CXR with multifocal infiltrates Sputum smear positive x 3 Xpert positive, rifampin resistant What do you do next? Start MDR treatment Pyrosequencing or MDDR Start RIPE Repeat Xpert on another specimen Start treatment for mono-rif resistance 4

42 Case 3 RIPE started PSQ: katg/inha: no mutation = INH Sens rpob: 4TTT silent mutation: RIF Sens 4

43 Case 4 US born high school student coughing x 6 months Sputum smear negative x 3 CXR: bilateral cavities Xpert positive: rifampin resistance What do you do next? Start MDR treatment Pyrosequencing or MDDR Start RIPE Repeat Xpert on another specimen 43

44 Case 4 PSQ showed no RIF mutations or INH mutations RIPE started Large contact investigation planned dose INH/Rifapentine regimen planned for infected contacts 44

45 How to interpret molecular test for resistance Put into clinical and epidemiologic context! Confirm non-sequencing tests (e.g., Xpert) with sequencing test Consider Rif resistance on Xpert to be MDR (not just rifampin monoresistant) Can usually treat based on sequencing test results; follow the growth based DST results 4

46 Case 3 year old male from Mexico diagnosed with smear-positive, pulmonary TB PSQ results katg mutation: Associated with INH resistance rpob mutation 6AAC: Not associated with RIF or RFB resistance. Growth-based DST results: INH resistance only Treated with RIF, EMB, PZA for 9 months End of treatment sputum: smear and culturepositive 46

47 Studies of Discordant Rifampin Results

48 Summary Drug resistance can be identified faster with molecular tests Confirm nonsequencing results (e.g., Xpert) with sequencing Beware the silent mutation! Keep clinical picture in mind investigate further if result unexpected Consult experts for unusual mutations 48

49 Consult experts when you feel like your head is going to explode! 49

50 Questions The findings and conclusions in this presentation are those of the presenter and do not necessarily represent the views of CDC.