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Download Do we have a good test of susceptibility for yeasts?
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Identification, Susceptibility & Resistance Dr Caroline B. Moore Mycology Reference Centre University Hospital of South Manchester The University of Manchester Yeasts Why bother with identification & susceptibility testing? • Significant number of invasive fungal infections • Increase in ‘at-risk’ patient population Why bother with identification & susceptibility testing? • Significant number of invasive fungal infections • Increase in ‘at-risk’ patient population • Increase in non-C. albicans species • Increase in ‘rarer’ species Proportion of nosocomial Candida infections caused by different species in a teaching hospital C.albicans 50 C.tropicalis 45 C.parapsilosis 40 C.glabrata Percentage 35 C.krusei 30 25 20 15 10 5 0 87-88 88-89 89-90 90-91 Year Berrouane et al. J Clin Micro 1999; 37:531 91-92 92-93 93-94 Why bother with identification & susceptibility testing? • Significant number of invasive fungal infections • Increase in ‘at-risk’ patient population • Increase in non-C. albicans species • Increase in ‘rarer’ species • Increase in drug resistance Increasing fluconazole resistance in Intensive Care Unit 600 100 90 500 80 70 400 DDD 300 50 40 200 30 20 100 10 1996 1995 1994 1993 0 1992 0 % FCZ Res Fluconazole 60 Moore et al. ECMM 1998 Amphotericin C. tropicalis C. glabrata C. albicans C. krusei Why bother with identification & susceptibility testing? • Significant number of invasive fungal infections • Increase in ‘at-risk’ patient population • Increase in non-C. albicans species • Increase in ‘rarer’ species • Increase in drug resistance • More drug choices available • Informed therapeutic choice How do we identify yeasts? • Culture morphology Chromagar How do we identify yeasts? • Germ tube test • Microscopic morphology • Other tests Terminal chlamydospores Arthrospores How do we identify yeasts? • Traditional methods – Wickerham tests Auxacolor • Commercial kits – numerous! Vitek-2 API ID 32C • Molecular methods MICs He uses statistics like a drunken man uses lamp-posts ... For support rather than illumination Do we have a good test of susceptibility for yeasts? • CLSI (NCCLS) M27-A3 method – USA standard • EUCAST Document E-Def 7.1 method – European standard Extensive clinical correlation work Do we have a good test of susceptibility for yeasts? • Disc diffusion – no MIC obtained – screening method • E-test strips – MIC value obtained – problematic endpoints Do we have a good test of susceptibility for yeasts? • An array of commercial formats – Vitek-2 – YeastOne – Fungitest – Others… Some are more equal than others! • Molecular methods Candida albicans • • • • • Most common cause of candidosis (50-70%) Can cause a wide range of diseases May cause vaginal and oral/oesophageal thrush Produces germ tubes Attributable mortality (18-25%) – differences in patient age and underlying illness Candida albicans • Azole susceptibility can depend on HIV status C.albicans C.albicans FLU-resistant FLU ITR VOR POS AMB 5FC CASP ++ ++ ++ ++ ++ ++ ++ - + ++ + ++ ++ ++ Rates of resistance seen in our laboratory 1992-2006 flucytosine 6% fluconazole 1.2% 5% of C. albicans with reduced susceptibility Candida parapsilosis complex • Candida parapsilosis, Candida orthopsilosis, Candida metapsilosis • 2nd most common species in blood, related to catheters and glucose solutions including TPN • Often seen in neonates • Generally do not cause thrush • Less pathogenic than C. albicans Candida parapsilosis complex FLU ITR VOR POS AMB C.parapsilosis ++ ++ ++ ++ ++ Rates of resistance seen in our laboratory 1992-2006 fluconazole 0.4% 5FC CASP + - Candida glabrata • • • • 3rd or 4th most common species in blood Increasing in many institutions Common cause of thrush, particularly vaginal Generally thought as unable to produce pseudohyphae in vitro • Evidence of ability to grow as filamentous organism Candida glabrata • Usually reduced susceptibility to fluconazole • Responds poorly to amphotericin B C.glabrata FLU ITR VOR POS AMB + + + + + 5FC CASP ++ ++ Rates of resistance seen in our laboratory 1992-2006 fluconazole 53% Candida tropicalis • Usually 4th most common species in blood, much commoner in some institutions • Generally does not cause thrush • More invasive than other Candida species • High attributable mortality (33-50%) • High frequency (~80-100%) of infection if coloniser during neutropenia Candida tropicalis • Usually fluconazole susceptible, but may develop resistance quickly C.tropicalis FLU ITR VOR POS AMB + ++ ++ ++ ++ 5FC CASP ++ ++ Rates of resistance seen in our laboratory 1992-2006 flucytosine 20% fluconazole 46% Candida krusei • 5th most common species in blood • Does not cause thrush, except in late-stage AIDS • High mortality in leukaemic patients Candida krusei • May be a breakthrough species • Always fluconazole resistant and amphotericin intermediate C.krusei FLU ITR VOR POS AMB - + + + + 5FC CASP + ++ Cryptococcus neoformans • Neurotropic fungus • Most common predisposing factor is AIDS • Also organ transplant recipients or cancer patients receiving chemotherapeutics • Produces a polysaccharide capsule - major virulence factor Cryptococcus neoformans • Combination therapy generally used Crypto. neoformans FLU ITR VOR POS AMB + + ++ ++ ++ 5FC CASP + - Image Courtesy of Carsten Kettner Rhodotorula mucilaginosa Saccharomyces species Malassezia species High degree of mortality Species of…. Trichosporon Geotrichum Blastoschizomyces Can be intrinsically resistant to some antifungal drugs Moulds - the Aspergilli Increasing incidence of invasive aspergillosis in hematopoietic stem cell transplant recipients 14 12 Incidence (%) 10 Allograft recipients 8 Autograft recipients 6 4 2 0 1990 1991 1992 1993 1994 1995 1996 1997 1998 Year Marr et al. Clin Infect Dis 2002; 34:909 What tests do we have to identify moulds? • morphology • microscopy Experience! • additional tests • molecular methods Aspergillus Wide spectrum of disease – dependent on immune status • Allergic bronchopulmonary aspergillosis • Pulmonary aspergilloma • Invasive aspergillosis Can be a secondary pathogen in cases of carcinoma or TB Aspergillus fumigatus complex most common cause of aspergillosis ~90% of cases Aspergillus niger complex Common cause of ear infections Aspergillus terreus complex Cause of superficial, eye, ear and systemic infections Aspergillus flavus complex Cause of pulmonary and sinus infections In vitro susceptibility of filamentous fungi ITR VOR POS AMB 5FC CASP FLU Asp. fumigatus ++ ++ ++ ++ +/- ++ - Asp. niger ++ ++ ++ ++ - ++ - Asp. terreus ++ ++ ++ - - ++ - Asp. flavus ++ ++ ++ ++ - ++ - Azole resistance in A. fumigatus complex Itraconazole • recent literature 0 - 5% • 7% RMLM 1992 – 2007 (n = 519) • significant increase in resistance since 2004 – now 13% Itraconazole resistant isolates • 58% cross-resistant to voriconazole • 66% cross-resistant to posaconazole Data from Dr Susan Howard MIC mg/L Azole cross resistance of Asp. fumigatus complex Mosquera & Denning. Antimicrob Agents Chemother 2002; 46:556 Other Aspergilli Klich MA. Identification of common Aspergillus species (2002). CBS. Non-Aspergillus moulds Increasing frequency of non-Aspergillus mould infections in hematopoietic stem cell transplant recipients 16 14 Infections (no.) 12 10 Fusarium spp 8 Zygomycetes Scedosporium spp 6 4 2 0 1985-1989 1990-1994 1995-1999 Time period Marr et al. Clin Infect Dis 2002; 34:909 Fusarium spp. Range of disease from cutaneous through to disseminated infection Scedosporium spp. Can cause subcutaneous infections but dissemination may occur in immunocompromised host Mucorales Cunninghamella Rhizomucor Rhizopus Absidia Mucor etc… In vitro susceptibility of filamentous fungi ITR VOR POS AMB 5FC CASP FLU Asp. fumigatus ++ ++ ++ ++ +/- ++ - Asp. niger ++ ++ ++ ++ - ++ - Asp. terreus ++ ++ ++ - - ++ - Asp. flavus ++ ++ ++ ++ - ++ - Fusarium - + +/- +/- - - - +/- + +/- - - +/- - - - + + - - - Scedosporium Mucorales Others… Acremonium Wangiella Penicillium Paecilomyces Phialophora Cladophialophora Alternaria Plus many more… Take time to ‘know’ the fungus in your hospital…. Better the devil….
