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Second Line Drugs Susceptibility Testing: Study Progress Report Alex Sloutsky

Second Line Drugs Susceptibility Testing: Study Progress Report Alex Sloutsky Massachusetts State TB Laboratory Paris, 2005. B ACKGROUND: Clinical significance of DST.

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Second Line Drugs Susceptibility Testing: Study Progress Report Alex Sloutsky

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  1. Second Line Drugs Susceptibility Testing: Study Progress Report Alex Sloutsky Massachusetts State TB Laboratory Paris, 2005

  2. BACKGROUND: Clinical significance of DST • It is common among clinicians to assume that if culture is resistant to a particular drug in vitro, this drug will be ineffective in vivo. • In reality, prognostic value of pretreatment DST can vary greatly depending on patient-specific factors: - proportion of resistant bacteria - whether resistance is acquired or primary • Clinical significance of susceptibility testing becomes an issue due to spread of MDR TB.

  3. Resiissstaannsensitivity • DST reports list drugs as either “sensitive” or “resistant” which indicates that there are two widely different phenotypes. • In reality, resistant strains exhibit a continuum of phenotypes, some of which may be very similar to sensitive, wild-type strains. • The task of the laboratory is to classify the level of resistance of a strain of M. tuberculosis in relation to the established “resistance criteria” to a specific drug. • These “breakpoints” determine clinically significant level of resistance to a drug, i.e. high enough to affect the efficacy of treatment if the patient is treated with that drug

  4. Study Design: MSLI Lab • Well-defined representative samples of clinical isolates of M. tuberculosis: • PR strains have been obtained from patients who failed treatment with the regimens containing the corresponding drug; • Probably susceptible (PS) strains: from patients who have never taken anti-TB drugs (unless infected with drug resistant organisms). • Source of strains: KIT (Korea), Philippines (TDF), Latvia, Hong Kong, Boston (PIH collection). Total planned:250 strains. • MIC to 6 drugs are to be determined: ETH, PAS, KAN, CAP, CYC, OFL by two methods: Agar Plate Proportions and BACTEC. • 8 concentrations of each drug used to determine the MIC breakpoint.

  5. WORKLOAD AND WORKFLOW: Agar Plate Proportions Method Total time allotted per week is 14 hours

  6. WORKLOAD AND WORKFLOW: BACTEC Total time allotted per week for BACTEC is 46 hours

  7. BUDGET

  8. PROJECTED DURATION AND CURRENT STATUS OF THE PROJECT Total time per week for 6 strains tested by both methods is 60 hours. It was anticipated that it would take 250/6 = 42 weeks to completion (with no repeat testing and no data analysis). Personnel hired and trained Supplies purchased Forms for recording results created Up to date: 272 cultures tested by APP method (< 10 to be repeated) and 40 tested by BACTEC. ~230 cultures to go will take ~40 weeks or 10 months

  9. DATABASE

  10. Preliminary Data Analysis

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