Principles and Practice of Antimicrobial Susceptibility Testing. Microbiology Technical Workshop 25 th September 2013

Transcription

1 Principles and Practice of Antimicrobial Susceptibility Testing Microbiology Technical Workshop 25 th September 2013

2 Scope History Why Perform Antimicrobial Susceptibility Testing? How to Perform an Antimicrobial Susceptibility Test Isolate Method (phenotypic, special tests, genotypic) Drug Standards (how breakpoints are derived; CLSI, EUCAST, BSAC, CDS) Understanding An Antimicrobial Susceptibility Test Categorical interpretation rule Summary

3 History

4 Source: Source: Sir Alexander Fleming ( )

5 When I woke up just after dawn on September 28, 1928, I certainly didn't plan to revolutionize all medicine by discovering the world's first antibiotic, or bacteria killer. ButIsupposethatwasexactly whatidid.

6 Why Perform Antimicrobial Susceptibility Testing?

7 Empiric Therapy Investigations Definitive Therapy

8 Patient LAM 89 year old Chinese female Previously hospitalized 2 months ago for cystitis Urine culture ESBL positive E. coli Blood cultures negative Now admitted from the A&E with fever, dysuria and increased urinary frequency for 3 days Urine microscopy RBC 3, WBC > 2000, EC 0 Urine culture no bacterial growth Started empirically on IV Piperacillin/tazobactam

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10 Predict treatment outcome Guide selection of most appropriate agent Provide alternatives drug allergy, oral option

11 How to Perform an Antimicrobial Susceptibility Test

12 Isolate Method Drug Standards Results

13 Isolate Identity of bacterial isolate Normal flora Clinically significant number of colonies Predictable antibiotic susceptibility profile

14 Method Phenotypic Zone diameter Minimum inhibitory concentration (MIC) Special tests Genotypic Source: CLSI M100-S23E Performance Standards for Antimicrobial Susceptibility Testing - 23rd Informational Supplement

15 Source: Source: Disk Diffusion

16 Source: Etest(Epsilometer test)

17 Source:

18 Source: Source: Broth Macrodilution

19 Source: Source: Automated (Vitek2) Source:

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21 Source: D-Test for inducible clindamycin resistance

22 Cephalosporin Clavulanic acid Cephalosporin ESBL Detection (double-disk approximation)

23 Source: Source: Source: Source:

24 Drug Species to be tested Institution formulary Commonly used antimicrobials Availability of antimicrobial agent for testing Tailored to specific needs of institution Infectious disease physicians Clinical microbiologists Pharmacists Committees concerned with institutional formulary

25 Source:

26 Standards MIC distribution Wild-type Epidemiological cut-off (ECOFF) Pharmacokinetic Pharmacodynamic Clinical data

27 susceptible resistant increasing concentration of antibiotic

28 susceptible resistant increasing concentration of antibiotic

29 Source:

30 Source:

31 Source:

32 Standard Location Media Inoculum CLSI America, several areas of Europe, Asia, Australia Mueller-Hinton agar Mueller-Hinton agar with 5% sheep blood EUCAST Europe Mueller-Hinton agar Mueller-Hinton agar with 5% defibrinatedhorse blood + 20 mg/l β-nad BSAC United Kingdom Iso-Sensitest agar Iso-Sensitestagar with 5% defibrinatedhorse blood + 20 mg/l NAD CDS Australia Sensitest agar Sensitest agar with 5% horse blood 0.5 McFarland 0.5 McFarland 0.5 McFarland then dilute (refer to Table) Refer to Figure

33 Source: (Version 12 May 2013)

34 Source: (Version 12 May 2013)

35 Source: (Version 12 May 2013)

36 Source: (Sixth Edition)

37 Source: (Sixth Edition)

38 Source: CLSI M100-S23E Performance Standards for Antimicrobial Susceptibility Testing - 23rd Informational Supplement CLSI

39 Source: CLSI M100-S23E Performance Standards for Antimicrobial Susceptibility Testing - 23rd Informational Supplement

40 Source: EUCAST

41 Source:

42 Source: (Version 12 May 2013) BSAC

43 Source: (Sixth Edition) CDS

44 Source: (Sixth Edition)

45 Source: (Sixth Edition) Source: (Sixth Edition)

46 Understanding An Antimicrobial Susceptibility Test

47 Identify Test Report

48 Categorical Interpretation Category Interpretation Susceptible High likelihood of therapeutic success Resistant High likelihood of therapeutic failure Intermediate Uncertain therapeutic effect Drug concentration at body sites Buffer zone Susceptible-dose dependent (S-DD) Antifungal susceptibility testing Susceptibility dependent on achieving maximal possible blood level Nonsusceptible Often seen with new antimicrobial agents

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50 Source: Rex and Pfaller CID Has Antifungal Susceptibility Testing Come of Age?

51 Summary Antimicrobial susceptibility tests allows us to Predict treatment outcome Guide selection of most appropriate agent Provide alternatives Factors to consider Isolate Method Drug Standards Understanding the results Categorical interpretation rule

52 Source: Thank you for your attention! Dr Jamie Tan Registrar Department of Pathology Singapore General Hospital