Case. Case. Case. Case. Reference lab AST. Nelesh Govender, NICD 2013/03/08. Candida species: Antifungal susceptibility testing in 2013

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1 Nelesh Govender, NICD 13/3/8 se ndida species: Antifungal susceptibility testing in 13 Nelesh Govender National Institute for Communicable Diseases and University of the Witwatersrand, Johannesburg Elderly man Mitral valve replacement in 11 Repeat valve surgery in January 12 Post-operative admission to ICU ndida parapsilosis cultured from valve tissue obtained at surgery (= prosthetic valve fungal endocarditis) Fluconazole MIC = 8 µg/ml (S*) Voriconazole MIC =.5 µg/ml (S*) Amphotericin B MIC =.5 µg/ml (no breakpoints) Severe renal impairment *CLSI M27-S3 8 se IDSA recommendation for prosthetic valve IE AmB ± flucytosine OR caspofungin Valve replacement, if possible Suppressive treatment with fluconazole (if isolate S) for minimum 6 weeks post-surgery orlifelong if surgery not possible se Fluconazole mg daily chosen because caspofungin was not available Repeat blood cultures negative Initial clinical resolution During prolonged ICU admission: MRSA sepsis, treated with linezolid Break-through ndida parapsilosis bloodstream infection Fluconazole MIC = 16 µg/ml (SDD*) Voriconazole MIC = 4 µg/ml (R*) Amphotericin B MIC =.5 µg/ml (no breakpoints) Isolate submitted to reference lab for re-testing Pappas PG, et al. ClinInfect Dis 9. *CLSI M27-S3 8 Reference lab AST se MIC (μg/ml) tegory* Fluconazole 64 Resistant Voriconazole.5 Intermediate Anidulafungin 1 Susceptible Micafungin 1 Susceptible spofungin.5 Susceptible Amphotericin B.47 No breakpoints Flucytosine.25 Susceptible Posaconazole.3 No breakpoints Itraconazole.12 Susceptible Repeat valve replacement and patient changed to caspofungin Patient died due to sepsis-related complications *CLSI M27-S4 13 SASCM meeting, Protea Hotel ORT 1

2 Nelesh Govender, NICD 13/3/8 Outline CLSI vs. EUCAST Revised CLSI species-specific clinical breakpoints for: Fluconazole Voriconazole Echinocandins Detection of resistance in species with no CBPs CLSI vs. EUCAST standards for AFST Different? CLSI M27-A3 1 EUCAST EDef7.1 2 Test format No Broth microdilution Broth microdilution Wells Yes Round-bottomed Flat-bottomed Medium No RPMI 16 broth RPMI 16 broth Glucosecontent of medium Yes.2% 2.% Inoculum density Yes CFU/ml 5 CFU/ml Incubation temperature No 35 o C 35 o C MIC endpoint No 5% inhibition relative to growth control 5% inhibition relative to growth control Endpoint reading Yes Visual Spectrophotometric 1. CLSI M27-A Rodriguez-Tudela JL et al. Clin Microbiol Infect 8. Fluconazole PK/PD Dose range: 5 mg to mg daily Linear PK, i.e. direct correlation between dose and serum concentrations Very good distribution to CSF AFST, 13 FLUCONAZOLE BREAKPOINTS Time-dependent, concentration-independent fungistatic activity with prolongedin-vivo post-antifungal effect AUC/ MIC is the predictive PD parameter for efficacy (target = 25) AUC is almost exactly equal to daily dose in milligrams dose/ MIC is a surrogate PD parameter PfallerMA, et al. Drug Resist Updates 1. Molecular mechanisms of azole resistance Fluconazole ECVs and CBPs Resistance mechanism Molecularbasis CDR gene-encoded MDRgene-encoded S SDD R Altered target ERG11 Over-expression of target ERG11 promoter Bypass pathway ERG3 ECV ECV - ECV Respiratory deficiency with increased efflux pump expression Mitochondrial DNA Pfaller MA. American J Med 12. PfallerMA, et al. Drug Resist Updates 1. Pfaller MA. American J Med 12. SASCM meeting, Protea Hotel ORT 2

3 Nelesh Govender, NICD 13/3/8 --: Fluconazole ECVs and CBPs : Fluconazole ECVs and CBPs S SDD R SDD R ECV ECV - ECV Pfaller MA. American J Med 12. Pfaller MA. American J Med 12. Dose/MIC vs. outcome Validation of CBPs PfallerMA, et al. Drug Resist Updates 1. Pfaller MA. American J Med 12. Voriconazole PK/PD Two loading doses followed by 4mg/kg IV or - mg PO q12h Non-linear PK, i.e. nodirect correlation between dose and serum concentrations Reasonable distribution to CSF AFST, 13 VORICONAZOLE BREAKPOINTS Time-dependent, concentration-independent fungistatic activity with prolonged in-vivo postantifungal effect AUC/ MIC is the predictive PD parameter for efficacy (target 25) PfallerMA, et al. DiagnostMicrobiolInfect Dis 11. SASCM meeting, Protea Hotel ORT 3

4 Nelesh Govender, NICD 13/3/8 Molecular mechanisms of azole resistance Voriconazole ECVs and CBPs Resistance mechanism Altered target Molecularbasis CDR gene-encoded MDRgene-encoded ERG11 Over-expression of target ERG11 promoter Bypass pathway Respiratory deficiency with increased efflux pump expression ERG3 Mitochondrial DNA 1 ECV ECV - ECV - Pfaller MA. American J Med 12. PfallerMA, et al. Drug Resist Updates Simulated data : WT voriconazole MIC distribution of 5 ndida species --: Voriconazole ECVs and CBPs : Voriconazole ECVs and CBPs 1 ECV ECV - 1 ECV Simulated data : WT voriconazole MIC distribution of 5 ndida species Validation of CBPs AFST, 13 ECHINOCANDIN BREAKPOINTS Pfaller MA. American J Med 12. SASCM meeting, Protea Hotel ORT 4

5 Nelesh Govender, NICD 13/3/8 Echinocandin PK/PD Molecular mechanisms of resistance One loading dose followed by 5- mg IV daily Linear PK, i.e. direct correlation between dose and serum concentrations Poor distribution to urine, CSF and eye Concentration-dependent fungicidal activity with prolongedin-vivo post-antifungal effect AUC/ MIC is the predictive PD parameter for efficacy (target 1-) PfallerMA, et al. Drug Resistance Updates 11. Shapiro R S et al. Microbiol. Mol. Biol. Rev. 11;75: Echinocandin ECVs and CBPs --: Echinocandin ECVs and CBPs 1 1 ECV -- ECV S 1 1 ECV -- S I R ECV Simulated data : WT echinocandin MIC distribution of 5 ndida species Simulated data : WT echinocandin MIC distribution of 5 ndida species 1 1 : Micafungin ECVs and CBPs ECV : spofungin and Anidulafungin ECVs and CBPs S I R ECV Simulated data : WT echinocandin MIC distribution of 5 ndida species Simulated data : WT echinocandin MIC distribution of 5 ndida species SASCM meeting, Protea Hotel ORT 5

6 Nelesh Govender, NICD 13/3/8 1 1 : Echinocandin ECVs and CBPs ECV Simulated data : WT echinocandin MIC distribution of 5 ndida species Validation of CBPs Only three phase III studies (invasive candidiasis) Smaller patient numbers PfallerMA, et al. Drug Resistance Updates 11. What do when there are no CBPs Use ECVs to determine if the isolate is non-wt and less likely to respond to antifungal treatment, e.g. amphotericin B ECV = 2 µg/ml se (revisited) ndida parapsilosis cultured from valve tissue obtained at surgery (= prosthetic valve fungal endocarditis) Fluconazole MIC = 8 µg/ml (R) Voriconazole MIC =.5 µg/ml (I) Amphotericin B MIC =.5 µg/ml (probably WT strain) Avoid azoles Based on revised CBPs (CLSI M27-S4) Fungistatic drug not ideal for IE Summary CLSI and EUCAST methods are different but yield similar 24-h MICs CLSI and EUCAST CBPs have been harmonised to a large extent by using a similar evidence base Species-specific CBPs for common species Drug-specific CBPs in some instances ECVs have been determined for ndidaspecies (including many uncommon species) can use these cut-offs to detect potential mutants and for epidemiologic surveillance SASCM meeting, Protea Hotel ORT 6