1 / 17

British Society for Microbial Technology

British Society for Microbial Technology. The laboratory diagnosis of tuberculosis 25 years of progress. D A Mitchison St George’s, University of London. With assistance from FINDdiagnostics. Diagnostic testing at different levels of health system. Sputum: 25 years ago (1985).

brit
Download Presentation

British Society for Microbial Technology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. British Society for Microbial Technology The laboratory diagnosis of tuberculosis 25 years of progress D A Mitchison St George’s, University of London With assistance from FINDdiagnostics

  2. Diagnostic testing at different levels of health system

  3. Sputum: 25 years ago (1985) • Poor countries: Microscopy alone • Richer countries. Microscopy, LJ culture , DST • Advanced countries. Microscopy, Liquid culture, ID, DST

  4. Sputum bacteriology UK (1985) • Direct smears • Culture on LJ slopes (3-6 weeks) • Identification as M. tuberculosis • (Chemical; PNB, niacin, catalase) • Drug susceptibility tests (DSTs) • (Rifampicin screen)

  5. 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

  6. Direct smears Fluorescence v. Bright field microscopy Fluorescence: Introduced in 1940s. 5x more rapid than Bright field BUT: Mercury vapour bulb: Expensive. Limited life. Gradual decline. LED illumination introduced during past 5 years Find/Zeus collaboration

  7. Culture: solid v. liquid Solid: LJ slopes. 7H11 slopes or plates. Liquid: Early attempts high contamination. 1971 Selective medium paper (Mitchison et al J Med Microbiol 1971; 5: 165) Penta used in Bactec machine Automated liquid systems v. solid media Sensitive. Rapid. Contamination. NTMs v. TB.

  8. Genetic systems Sensitivity

  9. Culture, identification & DSTs HAINMDTBDR plusPCR & Line probe based 1. Identifies as TB complex. 2.DSTs for RIF & INH (95%) Can be used directly on sputum avoiding culture

  10. What to do about MDR TB?(MDR = Resistance to INH & RIF) Genetic tests for reserve drugs not adequate yet. Therefore cultures in liquid or on solid medium necessary as well as genetic techniques.

  11. Reserve drugs

  12. MGIT 960 Reserve Critical Concentrations 1Rusch-Gerdes S et al. JCM 2006;44:688-92. 2Rodrigues C et al. IJTLD; 2008;12:1449-55. 3Kruuner A et al. JCM 2006;44:811-8.

  13. DSTs Phenotypic Classic on LJ slopes or 7H11 plates. Takes 7 weeks +. MGIT or other automated liquid tests. Microcolony methods • Liquid medium: Mods. Sensitive, time consuming, ?dangerous • Solid medium: Thin layer agar (TLA): Quicker. Less dangerous

  14. Phenotype DSTThin-layer agar plate (TLA) method 7H11 thin layer plates made selective Each plate with up to 6 strains in quadrants Control: no drug PNB (p-nitrobenzoate): TB inhibited. INH 0.2 µg/ml RIF 2.0 µg/ml SM 2.0 µg/ml PZA 2,000 µg/ml nicotinamide etc

  15. What is drug resistance? Defined from distribution of MICs on ‘wild’ strains

  16. Studies of early bactericidal activity define the ‘therapeutic’ margin

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

More Related