DR.RAGHAVENDRA.H.GOBBUR

PROFESSOR OF PEDIATRICS

B.L.D.E.UNIVERSITY’S Shri.B.M.Patil MEDICAL COLLEGE ,BIJAPUR rhgobbur@gmail.com

Newer modalities in TB diagnosis Guest lecture given at state PEDICON 2011

DR.RAGHAVENDRA.H.GOBBUR PROFESSOR OF PEDIATRICS B.L.D.E.UNIVERSITY’S Shri.B.M.Patil MEDICAL COLLEGE ,BIJAPUR. rhgobbur@gmail.com

Newer modalities in TB diagnosis

• IGRA assay Interferon (IFN)-γ Assay• Microscopy LED• Culture :Liquid Medias: BACTEC,• BAC T/ALERT 3D, MGIT• DNA NAAT: Real-time PCR, LIPA• Enzyme Assay: ADA

QUANTIFERON-TB GOLD in place of Mantoux test .

INTERFERON G ASSAY (IGRA)

IFN-γ

QUANTIFERON-TB GOLD .

IN VITRO TEST

ESAT-6 ,CFP-10 synthetic peptides are used

(Absent in BCG and most NTM)

stimulate T-cells from infected people

releasing IFN-γ, from These T-cells

*early secretory antigenic target-6

**culture filtrate protein-10

LTBI V/S DISEASE ?

- TST V/S IGRA

QUANTIFERON-TB GOLD .• Objective , and controlled test

Reduces subjectivity in TB diagnosis• Simple diagnostic cut-off (> .35 IU/ml IFN-γ = + )

Straight forward positive/negative interpretation • Eliminates 2 step testing• No ‘booster’ effects in-vitro• Faster turn-around, results in 24 - 48 hours• Results are electronic (computer generated reports)

INDIAN STUDY USING QUANTIFERONTB GOLD• Dogra S, Narang P, Mendiratta DK, Chaturvedi P, Reingold AL, Colford JM Jr, Riley LW, Pai M.

Comparison of a

• whole blood interferon-gamma assay with tuberculin skin testing • . ( J Infect 2007; 54:267–76.)• Compared QFT to the TST in 105 children ( suspected of TB, or had contact with an index

case).

• 11 children (10.5%) were QFT positive, whereas the• TST was positive in 15 (15%) at ≥5mm, 11 (10.5%) at ≥10mm, or 4 (4%) at • ≥15mm• .

• Concordance of TST with QFT was high (95%) at the 10mm TST cut off

• All subjects with≥15mm TST , were QFT positive. • There were• no indeterminate QFT results, despite 40% children being <4 years old

, and 57% of them being malnourished.

SUMMARY of IGRA TESTING IGRAs are recommended for1. Contacts of active TB Close contacts (HIGH RISK) TST OR IGRA if either is positive, treat for “L TB I” (latent infection) Casual contacts (LOW RISK) can have IGRA confirmation if TST is positive to verify infection v/s BCG or MOTT2. Immune compromised “suspected child" TST first, if negative do IGRA and if IGRA positive treat as LTBI

M.TB. STAINING BY ZEIL-NEILSON STAIN

• >1,000 Organism per ml sputum required for ordinary microscope.

• Fluorescent, LED microscope detects even 100 M.TB. organism per ml

AFB + SPUTAM SMEAR

FIND and Carl Zeiss fluorescent LED microscope based on the proven Primo Star platform.( FIND/Zeiss microscope offers superior optics, reflected light illumination, easy switch from bright field to fluorescent light)

MYCOBACTERIAL CULTUREMYCOBACTERIAL CULTURE

Culture remains the gold standard for lab confirmation of TB

Advantages:

Increases number of case detection Detects cases among smear negative patients Establishes viability of organisms Distinguishing between Mycobacterial species Helps in performing DST (drug sensitivity test) Helps in diagnosing cases of treatment failure

Limitations:

Expensive Require enriched media Require considerable expertise Time consuming

Processing of sputum with CPC MethodProcessing of sputum with CPC Method

If delay of more than 48 hours between collection and processing is anticipated, the sputum should be collected with 1%CPC and 2%NaCl2

CPC acts as homogenizing and decontaminating agent

It helps in retaining viability of Tubercle bacilli up to 7 days

These specimens should not be treated with NaOH ( Petroff’s)

Culture: Extra-Pulmonary SamplesCulture: Extra-Pulmonary Samples

Aseptically collected samplesBody fluids:Spinal ,Pleural, Pericardial, Synovial, ascitic, Blood, Pus & Bone marrowTissues:Lymph node, Needle biopsies or Tissue biopsiesSpecimens known to contain contaminating flora:Gastric lavage, Bronchial washings & Urine

L J MEDIA

CORD LIKE GROWTH OF M.TB. IN MEDIA

NEWER CULTURE METHODS for M.TB.NEWER CULTURE METHODS for M.TB.

• Microscopic Observation of Broth Culture &• MODS Micro Colony Detection System (slide culture)• Septi-check AFB : Non radiometric, Non automated• MGIT 960 : Automated. monitors every 60min.

O2 utilization, Intensification of O2 quenching fluorescent dye

• MB/BAC T - ALERT : Non radiometric, colorimetric detection of CO2

• BACTEC Radiometric

BACTEC 460 TB System(radio metric)BACTEC 460 TB System(radio metric) Developed in 1969 by Deland and Wagner.

Principle BACTEC 12B vial , utilize 14C labeled substrate (fatty acid) On inoculation, mycobacteria, grow & release 14CO2. The BACTEC instrument measures quantitatively the radioactivity

on a scale ranging from 0-999, as GI.(Growth Indicator) The daily increase in GI is proportional to growth in the medium. DST Drug Susceptibility Test When ATT is introduced in the medium reduced production of 14CO2 and decrease in GI.

MB BACT-ALERT 3DLIGHT EMITTING SENSORS

The MGIT 960 System

The MGIT 960 system is a non-radiometric automated system that uses the MGIT media & sensors to detect the fluorescence.

Advantages:

-The system holds 960 plastic tubes which are continuously monitored.

- Early detection with the machine monitoring & reading the tubes every hour.

II Mycobacteria Growth Indicator Tube (MGIT)

Tube contains modified Middle brook 7H9 broth base with OADC enrichment & PANTA antibiotic mixture.

All types of clinical specimens, pulmonary as well as extra-pulmonary ( except blood ) could be cultured on this type of media.

The OADC supplement

O ----- Oleic acid ( Metabolic stimulant)

A ----- Albumin ( to bind toxic free fatty acid )

D ---- Dextrose (Energy source )

C ----- Catalase ( Destroy toxic peroxides that may be present in the medium )

The PANTA antibiotic mixture

P ---- Polymyxin B A ---- Amphotericin B N ---- Nalidixic acid T ---- Trimethoprim A ---- Azlocillin+/- Vancomycin

The antibiotic mixture inhibits the growth of contaminating bacteria.

Principle of the procedure:(MGIT)

A fluorescent compound (which is sensitive to O2) is embedded in silicone on the bottom of the tube.

The actively respiring microorganisms consume the oxygen & allow the fluorescence to be observed using UV trans-illuminator lamp.

III Polymerase Chain Reaction (PCR) & Gene probe

Nucleic acid Amplification Tests polymerase enzymes amplify specific DNA sequences, using Nucleic acid probes, using DNA extracted from MTB in the sample.

Advantages:

- Rapid procedure ( 3 – 4 hours)

- High sensitivity (1-10 bacilli / ml sputum)

CDC recommends NAAT for all suspected TB cases

PCR ASSAY The thermal cycling, DNA melting separates the strands of DNA double helix at 95°C Heat-stable DNA Taq polymerase, ( Bacteria Thermus aquaticus.) Enzymatically assembles new DNA strands(selectively amplify ) using DNA primers ( DNA oligonucleotides.) & template(each strand) at 55 °C The selectivity of PCR results from the use of primers that are complementary to the DNA region targeted for amplification under specific thermal cycling conditions.

RR

REALTIME-PCR ASSAY• A TB specific primer and probe mix is provided and

this can be detected through the FAM channel.• The primer and probe mix exploits the so-called

TaqMan® principle.• During PCR amplification, forward and reverse primers

hybridize to the TB DNA/Cdna• . A fluorogenic probe is included in the same reaction

mixture , it consists of a DNA probe labelled with a • 5`-dye (reporter) and a 3`-quencher. (5’3’DQ)• During PCR amplification, the probe is cleaved and the

Reporter dye and Quencher are separated.• The resulting increase in fluorescence can be detected

on a range of real-time PCR platforms

PCR ASSAY• The PrimerDesign™ genesig Kit for Mycobacterium

Tuberculosis (TB) Genomes is designed• for the in vitro quantification of TB genomes. • The kit is designed to have the broadest detection profile

possible whilst remaining specific to the TB genome.• The primers have 100% homology with all other reference

sequences in the NCBI database.• Fig 1 Accession numbers for detected TB isolates.• CP000717.1, CP000611.1, AM408590.1, U43540.1,

AE000516.2, BX842583.1, BX842577.1,• BX842572.1, BX248339.1, U35021.1, U35017.1,

AF041819.1, BX248346.1, BX248334.1,

Disadvantages:

- Very expensive.- Require specialist training & equipment.- False positive results.( CONTAMINATION)

- Can not differentiate between living & dead bacilli. .

- Sputum specimens (3%--7%) might contain inhibitors that prevent or reduce amplification and cause false-negative NAA results.

RAPID RECOGNITION OF DRUG RESISTANCE

• PCR PROBES ARE AVAILABLE

• KAT-gene INH RESISTANCE• RPO gene RIFAMPICIN RESISTANCE• GYR –A FLUROQUINOLOE RESISTANCE• LIPA( Line Probe Assay ) amplified DNA is applied to

strips with probe for M.TB. And Rif. resistance

MODS versus other culture methodsMODS versus other culture methods**

Method

Pos.eachMethod(%)

Pos. byatleast one

cult.(%)

Sens. %

Mediandetection

days

Auramine 0 76 98 78

MODS 89 97 92 9 (4-31)

MGIT 88 95 93 10 (3-39)

LJ 73 96 76 24 ( 6-59)

Micro COL

7H1175 96 78 14.5(4-28)

PCR 81 90 90* Based on 172 samples

Caviedes.L. et al J..Clin.Microbiol. 2000, 38, 1203

Identification of M. tuberculosisIdentification of M. tuberculosisfrom the growthfrom the growth

Growth temperature 35o-37oC onlyNo pigmentationNiacin positiveCatalase negative at 68oCNo growth on LJ medium containing PNBPositive reaction for nitrate reduction

Differentiation of MycobacteriaDifferentiation of Mycobacteria

M.tuberculosis NTM

Colony morphology

Rough, eugonic Mostly smooth

Growth at 37oC + +/ -

Growth at 25oC - +

Pigmentation - +/ -

Niacin + -

PNB - +

Nitrate reduction + -

Catalase at 68oC - +

Can high drug dosage still have an effect on resistant strains?

Isoniazid Mutants katG – high MIC

inhA – low MIC

Early clinical trial

Guinea-pig study

Quinolones Mutants Mainly in gyrA – low MIC

Evaluation of different methods of diagnosis

As regards the time:

MGIT shortest time to positivity at 13.3 days

BACTEC 460 system 14.8 days

& for L J medium 25.6 days .

As regards the no. of culture yield:

The best yield, was with BACTEC 460, followed by BACTEC MGIT 960 , & then with L J medium.

As regards contamination rate:

L J medium (17%) had the highest contamination rate (Tortoli E, Cichero P,Et al. 1999) then the MGIT 960 ( 10.0% )

Compared with radiometeric system (3.7%)

SUMMARYUseful newer modalities

3idiots?

• QUANTIFERON-TB GOLD

• MB BACT-ALERT 3D LIGHT EMITTING SENSORS

• PCR PROBES for antibiotic resistance • INH,REF,ETH,FLORO Q

Tuberculosis (TB) Diagnostic Tests in Use, Recently Endorsed by the World Health Organization (WHO), and in Later Stages of Development.

Dorman S E Clin Infect Dis. 2010;50:S173-S177

© 2010 by the Infectious Diseases Society of America

Tuberculosis (TB) Diagnostic Tests in Use, Recently Endorsed by the World Health Organization (WHO), and in Later Stages of Development.

• BACTEC Myco/F Sputa Culture Medium, for �use with the BACTEC 9000MB System to detect mycobacteria species in clinical samples.

• BACTEC Myco/F Lytic.

• Dogra S, Narang P, Mendiratta DK, Chaturvedi P, Reingold • AL, Colford JM Jr, Riley LW, Pai M. Comparison of a whole • blood interferon-gamma assay with tuberculin skin testing • for the detection of tuberculosis infection in hospitalized • children in rural India. J Infect 2007; 54:267–76.• An Indian study that compared QFT to the TST in 105 children who • were suspected of having TB, or had contact with an index case. • In this study 11 children (10.5%) were QFT positive, whereas the TST • was positive in 15 (15%) at ≥5mm, 11 (10.5%) at ≥10mm, or 4 (4%) at • ≥15mm. Concordance of TST with QFT was high (95%) at the 10mm • TST cut-off. All ≥15mm TST subjects were QFT positive. • There were no indeterminate QFT results, despite 40% of the children • being <4 years old and 57% of them being malnourished.

SUMMARYIGRAs are recommended for1. Contacts of active TBClose contacts (HIGH RISK) can get both TST and IGRA and if either is positive, be treated for LTBICasual contacts (LOW RISK) can have IGRA confirmation if TST positive to verify infection vs BCG or MOTT2. Immune compromisedTST first, if negative do IGRA and if IGRA positive treat as LTBI3. Low risk people who are TST positiveDo an IGRA, if positive consider as LTBI

FIND and Carl Zeiss Micro Imaging GmbH have co- developed a fluorescent LED microscope based on the proven Primo Star platform. FIND/Zeiss microscope offers superior optics, reflected light illumination, easy switch from brightfield to fluorescent light

Components of the post-research-and-development process for promising new tuberculosis (TB) diagnostic technologies.

Dorman S E Clin Infect Dis. 2010;50:S173-S177

© 2010 by the Infectious Diseases Society of America

Reporting of culture resultsReporting of culture results

Reading

No Growth

1 – 19 colonies

20-100 colonies

>100 colonies

Confluent growth

Contaminated

Report

• Negative

• Positive ( No.of colonies)

• Positive (1+)

• Positive (2+)

• Positive (3+)

• Contaminated

INDIAN STUDY USING QUANTIFERONTB GOLD• Dogra S, Narang P, Mendiratta DK, Chaturvedi P, Reingold AL, Colford JM Jr, Riley LW, Pai M.

Comparison of a

• whole blood interferon-gamma assay with tuberculin skin testing • for the detection of tuberculosis infection in hospitalized • children in rural India. J Infect 2007; 54:267–76.• Compared QFT to the TST in 105 children ( suspected of TB, or had contact with an index

case). • 11 children (10.5%) were QFT positive, whereas the• TST was positive in 15 (15%) at ≥5mm, 11 (10.5%) at ≥10mm, or 4 (4%) at • ≥15mm.

• Concordance of TST with QFT was high (95%) at the 10mm • TST cut-off. All ≥15mm TST subjects were QFT positive. • There were no indeterminate QFT results, despite 40% of the children • being <4 years old and 57% of them being malnourished.

Thank you