Rapid Diagnosis of Invasive Fungal Disease in the ICU

Transcription

1 Rapid Diagnosis of Invasive Fungal Disease in the ICU Anna Lau Centre for Infectious Diseases & Microbiology & The University of Sydney Westmead Hospital NSW, Australia

2 IFD in the ICU Invasive candidiasis ~10% ICU infections (? underestimated) 2/3 nosocomial Candidemia 3 rd most common nosocomial BSI in ICU Aust: ICU-acquired candidemia 56% crude 30 d mortality (median 7 d) (Marriott et al, Crit Care 2009) Excess costs ~US$1-4 billion/yr ~55% non-c. albicans candidemia (15 species) ACS, PATH (Chen et al, EID 2006; Horn et al, CID 2009) C. glabrata 48%

3 Rationale for early diagnosis Early and appropriate antifungal intervention improves outcomes Risk factors Prolonged ICU LOS Greater disease acuity Broad-spectrum antibiotic receipt TPN receipt Corticosteroid & other immunosuppressive agents Haemodialysis Central venous catheterisation Gastrointestinal perforation Abdominal surgery Pancreatitis Burns Diabetes Prolonged mechanical ventilation (Ostrosky-Zeichner et al, Crit Care Med 2006) Candidemia is late and acute in onset Culture-directed treatment adjustments do not improve outcomes in critically ill pts empiric, pre-emptive therapy

4 Blood culture Gold standard Isolate, susceptibility testing, optimise therapy Slow (24-72 h) Insensitive (~50% IC; <10% IA; 40% Fusarium detected) BACTEC system (Horvath et al, JCM 2007) 15 Candida sp.; 10/100/1000 cfu into O 2, AnO 2 and mycology 479/648 (74%) flagged pos (98% O 2, 27% AnO 2, 97% M) Pos terminal subcultures 161/169 (95%) C. lipolytica neg all media Presumptive id C. glabrata if AnO 2 flagged before O 2 (Sens 94.9%; Spec 97.5%; PPV 93.3%; NPV 98.3%) (Foster et al, JMM 2007) *** 1-10 cfu/ml blood: 10 ml inoculation only 100 cfu

5 Rapid identification methods Direct from blood culture PNA FISH (AdvanDx) Germ tube Nucleic acid detection Surrogate markers (1 3)-β-D-glucan Candida mannan; Candida anti-mannan Nucleic acid detection

6 Identification direct from BC: PNA FISH Peptide nucleic acid fluorescence in situ hybridisation (AdvanDx Inc., USA) Synthetic DNA mimics (probes) Hybridise to complementary DNA target seq 28S rdna polymorphisms Candida species probes FDA approved for clinical use Fluorescence microscopy or flow cytometry

7 Identification direct from BC: PNA FISH probes C. albicans probe Dual-labeled probe C. albicans/c. glabrata Yeast Traffic Light probe C. albicans/c. parapsilosis C. glabrata/c. krusei C. tropicalis Shepard et al, JCM 2008;

8 Identification direct from BC: PNA FISH Advantages % sens, spec, PPV, NPV Easy & accurate h Minimal space & training Daily quality control slides Rx costs US$1837/pt caspofungin use (Alexander et al, DMID 2006) (Della-Latta et al, ECCMID 2008) Limitations Blood culture/culture isolates only US$30-80 Start-up equipment & ongoing costs Cross-rx: N. delphensis, C. bracarensis, C. nivariensis (C. glabrata) C. orthopsilosis (C. albicans) (Shepard JCM 2008; Gherna JCM 2009; Wu ECCMID 2007; Wilson JCM 2005)

9 Identification direct from BC: Germ tube test Traditionally performed on colonies from solid media (24-48 h) Presumptive id C. albicans C. albicans ~45% candidemias Practical, rapid (<3 h), cheap, simple 5% C. albicans germ tube neg False pos (C. dubliniensis, C. tropicalis) Ref N Sens Spec Terlecka et al, Mycoses % 100% Sheppard et al, %* 100% JCM 2008 Lee et al, ECCMID % 100% *neg GT on BC, pos GT on subculture Density of growth

10 Identification direct from BC: Nucleic acid detection Multiplex platforms Fungal species Fungal/bacterial 2 new rapid platforms MT-PCR NASBA-MB

11 Identification direct from BC: MT-PCR Multiplex-tandem PCR Nested PCR 11 fungal targets TAT <3 h <2 h without NA ext* Automated ~AUD$10/specimen (batched 6) 100% sensitivity, specificity (n=70) Missed detection of C. lambica, C. nivariensis & K. ohmeri Lau et al, JCM 2008; AusDiagnostics

12 Identification direct from BC: NASBA-MB Nucleic acid sequence based amplification-molecular beacon RNA template Isothermal system 41 C 3 enzymes (AMV-RT, RNase H; T7 RNA polymerase) TAT <3 h Potential for non-specific amplification N = 570 Probe Sens Spec PPV NPV Pan-gram pos 99.7% 100% 100% 90.7% Pan-gram neg 98.6% 95.9% 99.4% 99.4% Pan-fungal (n=10) 100% 100% 100% 100% Pan-Candida 100% 100% 100% 100% Pan-Asp N/A N/A N/A 100%? Adv over Gram s stain Zhao et al, JCM 2009

13 Rapid identification direct from BC: Summary Method TAT Cost/sample Adv Disadv PNA FISH h US $30-80 Simple, accurate, commercial Germ Tube <3 h AUD <$2 Simple, presumptive id Ca Cross rx, FM/FC False pos/neg, Ca only MT-PCR 2-3 h AUD $10 batched 11 major fungal bloodstream path, automated Miss rare sp. NASBA-MB <3 h AUD $10 Simple, isothermal RNA, genus id only *Large-scale, multi-centre clinical validations required

14 Surrogate markers for rapid screening & diagnosis Direct from whole blood or serum Serological assays (1 3)-β-D-glucan Candida mannan Ag; Candida anti-mannan Ab C. albicans germ tube Ab (CAGTA) Nucleic acid detection

15 (1 3)-β-D-glucan Cell wall All fungi except C. neoformans, Zygomycetes Presence in bloodstream = IFD Not present in bacterial, viral or mammalian cells Activates factor G of the horseshoe crab coagulation cascade Colorimetric detection Fungitell (Associates of Cape Cod, USA) FDA approved 2003 Fungitec-G (Seikagaku, Japan)

16 (1 3)-β-D-glucan: Fungitell Serum (1 pg/ml) Cut-off value 80 pg/ml Excellent NPV useful for excluding IFD Proven detection of IC, IA, fusariosis, trichosporonosis, PCP Ref Patients (n) Sens Spec PPV NPV Odabasi AML or MDS on AF CID 2004* prophylaxis (283) (16/4/33) Ostrosky- Zeichner JCM 2005 Persat JCM 2008 Desmet** JCM 2009 Proven/prob (163) 69.9%* Proven/prob IPA (70) Haem/ICU (122) BSI (27) PCP (20) 100% 90% (single pos) 64.4% 68% 85.2% 100% 96% (2 seq pos) 99% (3 seq pos) 87.1%* 92.4% 78% 70.5% HIV/haem malig PCP (28) 100% 96.4% *cut-off value 60 pg/ml; **100 pg/ml 43% 100% 83.8%* 89% 75.1%* 73% Proven+prob: BDG+ median 10 d before clinical diagnosis Prov+prob+pos: 70% BDG+ median 3 d before clinical diagnosis

17 Comparative evaluation IPA: 48/70 (68.6%) pos BDG 39/70 (55.7%) pos GM ELISA Candidemia: 20/27 (74.1%) pos BDG 11/27 (40.7%) pos mannan ELISA Persat et al, JCM 2008

18 (1 3)-β-D-glucan: Limitations No standardisation on cut-off values Patient population Type of IFD (Ostrosky-Zeichner et al, CID 2005) Species dependent (less sensitive for C. parapsilosis) panfungal character: combination with other diagnostic tests Very expensive duplicate/triplicates, serial testing False positives Hemodialysis with cellulose membranes Exposure to glucan containing materials (eg. gauze) Immunoglobulin preparations Albumin, coagulation factors, plasma protein fractions Gram positive bacteria (Streptococci) Pickering et al, JCM 2005

19 Other serological tests Test Sens Spec Platelia Candida mannan Ag EIA (Bio-Rad) 40% 98% Can-Tec LA test (Ramco Laboratories) % 98% Candida enolase 54-75% 100% Platelia Candida anti-mannan Ab EIA (Bio-Rad) 53% 94% SysCan3 (Rockeby Biomed) Healthy 74% IC 15% 75% 60% CAGTA IFA (Vircell) 77-89% % *performance dependant on patient subgroups Lau et al, Fut Microbiol 2009; Sendid et al, JCM 2004; Prella et al, DMID 2005; Philip et al, JCM 2005; Zargoza et al, CMI 2009

20 Commercial kit: LC SeptiFast kit First IVD PCR (Roche Diagnostics) for whole blood BAL for A. fumigatus (Steinmann et al, Transpl Infect Dis 2009) Multiplex PCR (25 species) Dual ITS-directed FRET probes Melt curve analysis 30 cfu/ml (except C. glabrata 100 cfu/ml)

21 Clinical evaluation: LC SeptiFast kit FUNGAL DETECTION ONLY Ref N pts studied Total Both BC & SF BC only SF only Westh CMI , general 37 5 (2 Ca/Cp; 1 Ct) 5 (2 Ca; 3 Cp) Louie 200, ED, ICU, 6 2 (Ca/Cp) 2 (Cg/Cp) 2 (Cp) CCM 2008 general Mancini JMM 2008 Casalta EJCMID 2008 Tsalik JCM 2009 Dierkes BMC ID neutropenic with haem malig (Af) 63, endocarditis (Cp) 0 27 (13 Ca; 12 Af; 2 Cp) 263, ED (Cg) 3 (Cg/Ck/Af) 77, general (3 Ca; 1 Ct) 6 (2 Ca; 1 Cg/Ck/Ct/Af)

22 Clinical evaluation: LC SeptiFast kit 100% species correlation fungi only Median time to pos: BC 2 d plus ID SeptiFast 18 h (if performed daily) Sensitivity for fungal detection SF 86% (32/37) vs BC 27% (10/37) (Westh et al, CMI 2009) Does DNAemia reflect true infection? Available for clinical use in Europe only $$ Adjunct to blood culture Warrants further clinical validation

23 Retrospective detection of candidemia by MT-PCR MT-PCR directly on EDTA WB (255), serum (29), plasma (24) (from 109 pts proven candidemia) MT-PCR pos 52/74 (70%) pts before BC flag+ and sp. ID Sens: 75% Spec: 97% PPV: 95% NPV: 85% Serum 71%, plasma 75%, WB 54% Lau et al JCM % neg where pos BC drawn sim - low fungal load - hepatic clearance - short ½ life circulating DNA

24 Whole blood v serum v plasma? No consensus Better performance in serum samples Free DNA (Metwally et al, JMM 2008; Kasai et al, JCM 2006; Bougnoux et al, JCM 1999; Lau et al, JCM 2010) Faster DNA extraction (1 h) Lack of standardisation

25 Rapid diagnosis IFD in ICU: Summary Method Adv Disadv Clinical risk factors (1 3)-β-D-glucan Data readily available, colonisation parameters improves performance Panfungal marker, excellent NPV, commercialised, treatment response Common in ICU Limited evaluation, false pos Mannan/antimannan >80% sens and spec in combined use Limited evaluation, requires serial testing NA detection Rapid, high specificity No standardisation, limited validation of commercial kits, $$ Culture Gold standard, antifungal susceptibility testing Insensitive, slow Combination of clinical risk prediction rules and non-culture based methods Use in conjunction with culture