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Korkmaz E, Ergon MC. Investigation of antifungal susceptibility of Aspergillus species isolated from systemic clinical specimens by different methods. Indian J Med Microbiol 2024; 50:100642. [PMID: 38830536 DOI: 10.1016/j.ijmmb.2024.100642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 05/30/2024] [Accepted: 05/31/2024] [Indexed: 06/05/2024]
Abstract
PURPOSE Due to the potential for Aspergillus species to cause lethal infections and the rising rates of antifungal resistance, the significance of antifungal susceptibility tests has increased. We aimed to assess the sensitivities of Aspergillus species to amphotericin B (AMB), voriconazole (VOR), itraconazole (ITZ), and caspofungin (CAS) using disk diffusion (DD) and gradient diffusion (GD) methods and compare them with broth microdilution (BMD) as the reference susceptibility method. METHODS The study involved 62 Aspergillus fumigatus, 28 Aspergillus flavus, and 16 Aspergillus terreus isolates, totaling 106 Aspergillus isolates. BMD and DD methods were performed in accordance with CLSI M38-A2 and CLSI M51-A documents, respectively. The GD method utilized nonsupplemented Mueller Hinton agar (MHA) as the medium. RESULTS In the BMD method, the lowest minimal inhibitory concentration (MIC)90 or minimal effective concentration (MEC)90 values were observed for VOR and CAS (0.5 μg/mL and 0.06 μg/mL, respectively). AMB and ITZ MIC90 values were both 2 μg/mL. In our comparison of the GD method with the BMD method at ±2 dilution, we observed essential agreement rates of 91.6%, 99.1%, 100%, and 38.6% for AMB, VOR, ITZ, and CAS, respectively. When comparing DD and BMD methods, we found categorical agreement rates of 65.1%, 99.1%, 77.3%, and 100% for AMB, VOR, ITZ, and CAS, respectively. For GD and BMD methods, these rates were 79.2%, 99.1%, 87.8%, and 100%. CONCLUSIONS Given the high essential and categorical agreement rates, we posit that the GD method is a viable alternative to the BMD method for AMB, ITZ and VOR but not for CAS. In addition, the use of nonsupplemented MHA in the GD method proves advantageous due to its cost-effectiveness and widespread availability compared to other growth media.
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Affiliation(s)
- Emine Korkmaz
- Dokuz Eylül University Faculty of Medicine, Department of Medical Microbiology, İzmir, Turkey.
| | - M Cem Ergon
- Dokuz Eylül University Faculty of Medicine, Department of Medical Microbiology, İzmir, Turkey.
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Meletiadis J, Siopi M, Kanioura L, Jørgensen KM, Perlin DS, Mouton JW, Arendrup MC. Development and multicentre validation of an agar-based screening method for echinocandin susceptibility testing of Aspergillus species. J Antimicrob Chemother 2020; 74:2247-2254. [PMID: 31106352 DOI: 10.1093/jac/dkz154] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 02/15/2019] [Accepted: 03/18/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Reference antifungal susceptibility testing of echinocandins against Aspergillus spp. relies on the determination of the minimal effective concentration, which is difficult to perform, time-consuming and subjective. We developed and evaluated in a multicentre study an agar-based screening method for echinocandin susceptibility testing of Aspergillus spp. METHODS Forty WT isolates [10 Aspergillus fumigatus species complex (SC), 10 Aspergillus flavus SC, 10 Aspergillus terreus SC and 10 Aspergillus niger SC] and 4 non-WT A. fumigatus isolates with or without known fks alterations were used. The optimal test conditions and stability over time were evaluated in preliminary studies monitoring colony growth. Twenty-microlitre aliquots of 1-2 McFarland inocula in 0.1% Tween 20 aqueous solution were added to each well and plates were incubated for 24/48 h at 35 ± 2°C. Subsequently, all isolates were tested blindly at three centres using four-well screening plates, containing anidulafungin, caspofungin, micafungin or no antifungal in each of the four wells, respectively. RESULTS WT isolates produced fluffy colonies on drug-free agar wells only. The non-WT isolates produced fluffy colonies on echinocandin-containing and control agar wells. Using the echinocandin concentrations of 0.25 mg/L anidulafungin, 1 mg/L caspofungin and 0.125 mg/L micafungin, and the compact (non-fluffy) versus fluffy colony morphology endpoint, all centres successfully discriminated non-WT and WT strains even after 24 h. Among the three echinocandins, anidulafungin produced the clearest endpoints. CONCLUSIONS The four-well plate agar method is suitable for echinocandin susceptibility screening of Aspergillus spp. and can be used to detect echinocandin non-WT isolates.
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Affiliation(s)
- Joseph Meletiadis
- Clinical Microbiology Laboratory, Attikon University General Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece.,Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Maria Siopi
- Clinical Microbiology Laboratory, Attikon University General Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Lamprini Kanioura
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands
| | | | - David S Perlin
- Public Health Research Institute, New Jersey Medical School, Rutgers Biomedical and Health Sciences, Newark, NJ, USA
| | - Johan W Mouton
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Maiken Cavling Arendrup
- Unit of Mycology, Statens Serum Institut, Copenhagen, Denmark.,Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark.,Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
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Chadeganipour M, Mohammadi R. A 9-Year Experience of Aspergillus Infections from Isfahan, Iran. Infect Drug Resist 2020; 13:2301-2309. [PMID: 32765006 PMCID: PMC7368557 DOI: 10.2147/idr.s259162] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 06/25/2020] [Indexed: 12/28/2022] Open
Abstract
Purpose Aspergillosis is an important fungal disease affecting millions of individuals worldwide. The genus of Aspergillus consist of various complexes, causing a wide spectrum of diseases from superficial infections in immunocompetent hosts to life-threatening disseminated infections among immunocompromised patients. This study aimed to identify Aspergillus species by phenotypic (total isolates) and molecular tests (35 isolates), obtained from patients in Isfahan (the third-largest city of Iran) between 2010 and 2018, and determine the susceptibility of 35 clinical isolates to itraconazole (ITR), amphotericin-B (AMB), and voriconazole (VOR). Patients and Methods Based on clinical signs, a total of 2385 suspected cases were included in this retrospective study from January 2010 to December 2018. Direct microscopic examination with potassium hydroxide, sabouraud dextrose agar with chloramphenicol, and czapekdox agar media was applied to identify etiologic agents. Thirty-five Aspergillus species collected from January 2016 to December 2018 were identified by PCR-sequencing of ITS1-5.8SrDNA-ITS2 region, and their susceptibility to ITR, AMB, and VOR was determined using E-test. Results Based on direct microscopy and positive culture, 132 out of 2385 suspected cases had Aspergillus infection (5.5%). Fifty-four patients were male, and 78 patients were female. Patients in the age groups of 41–50 and 21–30 years had the highest and lowest frequencies, respectively. Aspergillus flavus/oryzae (n=54), A. fumigatus (n=24), A. niger (n=15), and A. terreus (n=12) were the most prevalent Aspergillus species, respectively. Among 35 Aspergillus species, the MIC ranges of AMB, ITR, and VOR for A. flavus/oryzae, A. niger, and A. terreus were (0.5–4 μg/mL; 0.5–16 μg/mL; 0.25–8 μg/mL), (1 μg/mL, 1 μg/mL, 1 μg/mL), and (4–4 μg/mL, 0.5–1 μg/mL, 0.5–1 μg/mL), respectively. Conclusion Aspergillus infections have a wide spectrum of clinical manifestations and often occur in immunocompromised patients. Accurate identification at the species level is essential since the emergence of cryptic species is connected to different patterns of AFST that affect patient treatment outcomes. Azole-resistant Aspergillus spp. is a global concern, and the detection of the route of resistance is pivotal to prevent and control infection.
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Affiliation(s)
- Mostafa Chadeganipour
- Department of Medical Parasitology and Mycology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Rasoul Mohammadi
- Department of Medical Parasitology and Mycology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.,Infectious Diseases and Tropical Medicine Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
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Meletiadis J, Siopi M, Kanioura L, Jørgensen KM, Perlin DS, Mouton JW, Arendrup MC. A multicentre study to optimize echinocandin susceptibility testing of Aspergillus species with the EUCAST methodology and a broth microdilution colorimetric method. J Antimicrob Chemother 2020; 75:1799-1806. [PMID: 32330938 PMCID: PMC7303820 DOI: 10.1093/jac/dkaa102] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 02/20/2020] [Accepted: 02/26/2020] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The determination of the minimal effective concentration (MEC) of echinocandins against Aspergillus species is subjective, time consuming and has been associated with very major errors. METHODS The MECs/MICs of 40 WT [10 each of Aspergillus fumigatus species complex (SC), Aspergillus flavus SC, Aspergillus terreus SC and Aspergillus niger SC] and 4 non-WT A. fumigatus isolates were determined with EUCAST E.Def 9.3.1 read microscopically, macroscopically, spectrophotometrically and colorimetrically in three centres. The optimal conditions for spectrophotometric (single- versus multi-point readings) and colorimetric (XTT/menadione concentration and stability, incubation time) methods were evaluated in preliminary studies using different cut-offs for the determination of macroscopic, spectrophotometric and colorimetric MIC endpoints compared with the microscopically determined MEC. Inter-centre and inter-method essential (within one 2-fold dilution) agreement (EA) and categorical agreement (CA) were determined. RESULTS Both macroscopic and spectrophotometric endpoint readings showed poor inter-centre EA (53%-66%) and low CA (41%-88%) in distinguishing WT from non-WT A. fumigatus SC isolates, while significant differences compared with the microscopic MECs were observed for all echinocandins (EA 6%-54%). For the colorimetric method, the optimal conditions were 400 mg/L XTT/6.25 μΜ menadione, incubation for 1-2 h until the drug-free control reached an absorbance at 450/630 nm of >0.8 and use of 50% inhibition of XTT conversion as a cut-off for all species and echinocandins. All non-WT isolates had high XTT MICs >1 mg/L, whereas the overall inter-centre EA and CA were 72%-89% and 100%, respectively. CONCLUSIONS The XTT colorimetric assay improved the antifungal susceptibility testing of echinocandins against Aspergillus spp., reliably detecting non-WT isolates.
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Affiliation(s)
- Joseph Meletiadis
- Clinical Microbiology Laboratory, Attikon University General Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Maria Siopi
- Clinical Microbiology Laboratory, Attikon University General Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Lamprini Kanioura
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands
| | | | - David S Perlin
- Center for Discovery and Innovation, Hackensack Meridian Health, Nutley, NJ, USA
| | - Johan W Mouton
- Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Maiken Cavling Arendrup
- Unit of Mycology, Statens Serum Institut, Copenhagen, Denmark
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
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Dannaoui E, Espinel-Ingroff A. Antifungal Susceptibly Testing by Concentration Gradient Strip Etest Method for Fungal Isolates: A Review. J Fungi (Basel) 2019; 5:jof5040108. [PMID: 31766762 PMCID: PMC6958406 DOI: 10.3390/jof5040108] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 11/13/2019] [Accepted: 11/16/2019] [Indexed: 12/23/2022] Open
Abstract
Antifungal susceptibility testing is an important tool for managing patients with invasive fungal infections, as well as for epidemiological surveillance of emerging resistance. For routine testing in clinical microbiology laboratories, ready-to-use commercial methods are more practical than homemade reference techniques. Among commercially available methods, the concentration gradient Etest strip technique is widely used. It combines an agar-based diffusion method with a dilution method that determinates a minimal inhibitory concentration (MIC) in µg/mL. Many studies have evaluated the agreement between the gradient strip method and the reference methods for both yeasts and filamentous fungi. This agreement has been variable depending on the antifungal, the species, and the incubation time. It has also been shown that the gradient strip method could be a valuable alternative for detection of emerging resistance (non-wild-type isolates) as Etest epidemiological cutoff values have been recently defined for several drug-species combinations. Furthermore, the Etest could be useful for direct antifungal susceptibility testing on blood samples and basic research studies (e.g., the evaluation of the in vitro activity of antifungal combinations). This review summarizes the available data on the performance and potential use of the gradient strip method.
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Affiliation(s)
- Eric Dannaoui
- Paris-Descartes University, Faculty of Medicine, 75006 Paris, France
- APHP, European Georges Pompidou Hospital, Parasitology-Mycology Unit, Microbiology Department, 75015 Paris, France
- Correspondence: ; Tel.: +33-15-6093-948; Fax: +33-15-6092-446
| | - Ana Espinel-Ingroff
- Virginia Commonwealth University (VCU) Medical Center, Richmond, VA 23219, USA;
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Jenks JD, Spiess B, Buchheidt D, Hoenigl M. (New) Methods for Detection of Aspergillus fumigatus Resistance in Clinical Samples. CURRENT FUNGAL INFECTION REPORTS 2019; 13:129-136. [PMID: 31552129 PMCID: PMC6759225 DOI: 10.1007/s12281-019-00342-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
PURPOSE OF REVIEW The incidence of invasive aspergillosis has increased substantially over the past few decades, accompanied by a change in susceptibility patterns of Aspergillus fumigatus with increasing resistance observed against triazole antifungals, including voriconazole and isavuconazole, the most commonly used antifungal agents for the disease. Culture-based methods for determining triazole resistance are still the gold standard but are time consuming and lack sensitivity. We sought to provide an update on non-culture-based methods for detecting resistance patterns to Aspergillus. RECENT FINDINGS New molecular-based approaches for detecting triazole resistance to Aspergillus, real-time polymerase chain reaction (PCR) to detect mutations to the Cyp51A protein, have been developed which are able to detect most triazole-resistant A. fumigatus strains in patients with invasive aspergillosis. SUMMARY Over the last few years, a number of non-culture-based methods for molecular detection of Aspergillus triazole resistance have been developed that may overcome some of the limitations of culture. These molecular methods are therefore of high epidemiological and clinical relevance, mainly in immunocompromised patients with hematological malignancies, where culture has particularly limited sensitivity. These assays are now able to detect most triazole-resistant Aspergillus fumigatus strains. Given that resistance rates vary, clinical utility for these assays still depends on regional resistance patterns.
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Affiliation(s)
- Jeffrey D. Jenks
- Department of Medicine, University of California San Diego, San Diego, CA 92103, USA
| | - Birgit Spiess
- Department of Hematology and Oncology, Scientific Laboratory, University Hospital Mannheim, Heidelberg University, Pettenkoferstraße 22, 68169 Mannheim, Germany
| | - Dieter Buchheidt
- Department of Hematology and Oncology, Scientific Laboratory, University Hospital Mannheim, Heidelberg University, Pettenkoferstraße 22, 68169 Mannheim, Germany
| | - Martin Hoenigl
- Department of Medicine, University of California San Diego, San Diego, CA 92103, USA
- Section of Infectious Diseases and Tropical Medicine, Medical University of Graz, Graz, Austria
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Denardi LB, Keller JT, de Azevedo MI, Oliveira V, Piasentin FB, Severo CB, Santurio JM, Alves SH. Comparison Between Etest and Broth Microdilution Methods for Testing Itraconazole-Resistant Aspergillus fumigatus Susceptibility to Antifungal Combinations. Mycopathologia 2017; 183:359-370. [PMID: 28994001 DOI: 10.1007/s11046-017-0208-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 10/02/2017] [Indexed: 11/30/2022]
Abstract
The checkerboard broth microdilution assay (BMD) is the most frequently used method for the in vitro evaluation of drug combinations. However, its use to evaluate the effect of antifungal drugs on filamentous fungi is sometimes associated with endpoint-reading difficulties, and different degrees of interaction are assigned to the same drug combination. We evaluated combinations of the azoles, itraconazole, posaconazole, and voriconazole, with the echinocandins, anidulafungin, caspofungin, and micafungin, against 15 itraconazole-resistant Aspergillus fumigatus clinical strains via the checkerboard BMD and Etest assay. Readings after 24 and 48 h, considering the two reading endpoints, the minimum inhibitory concentration (MIC) and minimum effective concentration (MEC), were performed for both methods. Our results showed that the correlation coefficients between the BMD and Etest methods were quite diverse to the drug combinations tested. The highest correlation coefficients of the Etest with the BMD assays (MEC and MIC reading) were the Etest-MIC reading at 24 h and the Etest-MEC reading at 48 h. Improvements in experimental conditions may increase the correlation between the two methods and ensure that Etest assay can be safely used in the evaluation of antifungal combinations against Aspergillus species.
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Affiliation(s)
- Laura Bedin Denardi
- Postgraduate Program in Pharmaceutical Sciences, Health Sciences Center, Federal University of Santa Maria, Santa Maria, RS, 97105-900, Brazil.
- Mycological Research Laboratory, Federal University of Santa Maria, UFSM, Santa Maria, RS, Brazil.
| | - Jéssica Tairine Keller
- Postgraduate Program in Pharmaceutical Sciences, Health Sciences Center, Federal University of Santa Maria, Santa Maria, RS, 97105-900, Brazil
- Mycological Research Laboratory, Federal University of Santa Maria, UFSM, Santa Maria, RS, Brazil
| | - Maria Isabel de Azevedo
- Postgraduate Program in Pharmacology, Health Sciences Center, Federal University of Santa Maria (UFSM), Santa Maria, RS, Brazil
- Mycological Research Laboratory, Federal University of Santa Maria, UFSM, Santa Maria, RS, Brazil
| | - Vanessa Oliveira
- Mycological Research Laboratory, Federal University of Santa Maria, UFSM, Santa Maria, RS, Brazil
| | - Fernanda Baldissera Piasentin
- Postgraduate Program in Pharmaceutical Sciences, Health Sciences Center, Federal University of Santa Maria, Santa Maria, RS, 97105-900, Brazil
- Mycological Research Laboratory, Federal University of Santa Maria, UFSM, Santa Maria, RS, Brazil
| | | | - Janio Morais Santurio
- Postgraduate Program in Pharmacology, Health Sciences Center, Federal University of Santa Maria (UFSM), Santa Maria, RS, Brazil
- Mycological Research Laboratory, Federal University of Santa Maria, UFSM, Santa Maria, RS, Brazil
| | - Sydney Hartz Alves
- Postgraduate Program in Pharmaceutical Sciences, Health Sciences Center, Federal University of Santa Maria, Santa Maria, RS, 97105-900, Brazil
- Mycological Research Laboratory, Federal University of Santa Maria, UFSM, Santa Maria, RS, Brazil
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Gautier M, Normand AC, Ranque S. Previously unknown species of Aspergillus. Clin Microbiol Infect 2016; 22:662-9. [PMID: 27263029 DOI: 10.1016/j.cmi.2016.05.013] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 05/11/2016] [Accepted: 05/14/2016] [Indexed: 12/16/2022]
Abstract
The use of multi-locus DNA sequence analysis has led to the description of previously unknown 'cryptic' Aspergillus species, whereas classical morphology-based identification of Aspergillus remains limited to the section or species-complex level. The current literature highlights two main features concerning these 'cryptic' Aspergillus species. First, the prevalence of such species in clinical samples is relatively high compared with emergent filamentous fungal taxa such as Mucorales, Scedosporium or Fusarium. Second, it is clearly important to identify these species in the clinical laboratory because of the high frequency of antifungal drug-resistant isolates of such Aspergillus species. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) has recently been shown to enable the identification of filamentous fungi with an accuracy similar to that of DNA sequence-based methods. As MALDI-TOF MS is well suited to the routine clinical laboratory workflow, it facilitates the identification of these 'cryptic' Aspergillus species at the routine mycology bench. The rapid establishment of enhanced filamentous fungi identification facilities will lead to a better understanding of the epidemiology and clinical importance of these emerging Aspergillus species. Based on routine MALDI-TOF MS-based identification results, we provide original insights into the key interpretation issues of a positive Aspergillus culture from a clinical sample. Which ubiquitous species that are frequently isolated from air samples are rarely involved in human invasive disease? Can both the species and the type of biological sample indicate Aspergillus carriage, colonization or infection in a patient? Highly accurate routine filamentous fungi identification is central to enhance the understanding of these previously unknown Aspergillus species, with a vital impact on further improved patient care.
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Affiliation(s)
- M Gautier
- Aix Marseille Univ, Univ Montpellier 1, IRBA, IP-TPT, Marseille, France; Parasitologie & Mycologie, Hôpital de la Timone, Assistance Publique-Hôpitaux de Marseille, Marseille, France
| | - A-C Normand
- Parasitologie & Mycologie, Hôpital de la Timone, Assistance Publique-Hôpitaux de Marseille, Marseille, France
| | - S Ranque
- Aix Marseille Univ, Univ Montpellier 1, IRBA, IP-TPT, Marseille, France; Parasitologie & Mycologie, Hôpital de la Timone, Assistance Publique-Hôpitaux de Marseille, Marseille, France.
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Comparing Etest and Broth Microdilution for Antifungal Susceptibility Testing of the Most-Relevant Pathogenic Molds. J Clin Microbiol 2015. [PMID: 26202113 DOI: 10.1128/jcm.00925-15] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Invasive mold infections are life-threatening diseases for which appropriate antifungal therapy is crucial. Their epidemiology is evolving, with the emergence of triazole-resistant Aspergillus spp. and multidrug-resistant non-Aspergillus molds. Despite the lack of interpretive criteria, antifungal susceptibility testing of molds may be useful in guiding antifungal therapy. The standard broth microdilution method (BMD) is demanding and requires expertise. We assessed the performance of a commercialized gradient diffusion method (Etest method) as an alternative to BMD. The MICs or minimal effective concentrations (MECs) of amphotericin B, voriconazole, posaconazole, caspofungin, and micafungin were assessed for 290 clinical isolates of the most representative pathogenic molds (154 Aspergillus and 136 non-Aspergillus isolates) with the BMD and Etest methods. Essential agreements (EAs) within ±2 dilutions of ≥90% between the two methods were considered acceptable. EAs for amphotericin B and voriconazole were >90% for most potentially susceptible species. For posaconazole, the correlation was acceptable for Mucoromycotina but Etest MIC values were consistently lower for Aspergillus spp. (EAs of <90%). Excellent EAs were found for echinocandins with highly susceptible (MECs of <0.015 μg/ml) or intrinsically resistant (MECs of >16 μg/ml) strains. However, MEC determinations lacked consistency between methods for strains exhibiting mid-range MECs for echinocandins. We concluded that the Etest method is an appropriate alternative to BMD for antifungal susceptibility testing of molds under specific circumstances, including testing with amphotericin B or triazoles for non-Aspergillus molds (Mucoromycotina and Fusarium spp.). Additional study of molecularly characterized triazole-resistant Aspergillus isolates is required to confirm the ability of the Etest method to detect voriconazole and posaconazole resistance among Aspergillus spp.
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Perkhofer S, Mrazek C, Hartl L, Lass-Flörl C. In Vitro Susceptibility Testing in Fungi: What is its Role in Clinical Practice? Curr Infect Dis Rep 2011; 12:401-8. [PMID: 21308547 DOI: 10.1007/s11908-010-0134-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An increasing number of patients are undergoing transplantation procedures or receiving aggressive immunosuppression and chemotherapy. The growing population of immunocompromised hosts has led to a rise in the prevalence of invasive fungal infections due to yeasts and molds. The introduction of new antifungal agents and recent reports of resistance emerging during treatment of fungal infections have highlighted the need for in vitro susceptibility testing. Various testing procedures have been proposed, including macrodilution and microdilution, agar diffusion, disk diffusion, and Etest (AB Biodisk, Solna, Sweden). Establishing clinical correlation with antifungal susceptibility testing, however, is a huge challenge because susceptibility techniques do not take into account the dynamic and complex biology of fungi exposed to an antifungal in vivo. This paper reviews the available methods for antifungal susceptibility testing of yeasts and filamentous fungi and the data regarding the clinical implications of in vitro testing.
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Affiliation(s)
- Susanne Perkhofer
- Division of Hygiene and Medical Microbiology, Innsbruck Medical University, Fritz Pregl Strasse 3, 6020, Innsbruck, Austria,
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Howard SJ, Arendrup MC. Acquired antifungal drug resistance inAspergillus fumigatus:epidemiology and detection. Med Mycol 2011; 49 Suppl 1:S90-5. [DOI: 10.3109/13693786.2010.508469] [Citation(s) in RCA: 150] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Wild-type MIC distributions and epidemiological cutoff values for caspofungin and Aspergillus spp. for the CLSI broth microdilution method (M38-A2 document). Antimicrob Agents Chemother 2011; 55:2855-9. [PMID: 21422219 DOI: 10.1128/aac.01730-10] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Clinical breakpoints have not been established for mold testing. Epidemiologic cutoff values (ECVs) are available for six Aspergillus spp. and the triazoles, but not for caspofungin. Wild-type (WT) minimal effective concentration (MEC) distributions (organisms in a species-drug combination with no acquired resistance mechanisms) were defined in order to establish ECVs for six Aspergillus spp. and caspofungin. The number of available isolates was as follows: 1,691 A. fumigatus, 432 A. flavus, 192 A. nidulans, 440 A. niger, 385 A. terreus, and 75 A. versicolor isolates. CLSI broth microdilution MEC data gathered in five independent laboratories in Canada, Europe, and the United States were aggregated for the analyses. ECVs expressed in μg/ml that captured 95% and 99% of the modeled wild-type population were for A. fumigatus 0.5 and 1, A. flavus 0.25 and 0.5, A. nidulans 0.5 and 0.5, A. niger 0.25 and 0.25, A. terreus 0.25 and 0.5, and A. versicolor 0.25 and 0.5. Although caspofungin ECVs are not designed to predict the outcome of therapy, they may aid in the detection of strains with reduced antifungal susceptibility to this agent and acquired resistance mechanisms.
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High rate of Exophiala dermatitidis recovery in the airways of patients with cystic fibrosis is associated with pancreatic insufficiency. J Clin Microbiol 2011; 49:1004-9. [PMID: 21209163 DOI: 10.1128/jcm.01899-10] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The black-pigmented fungus Exophiala dermatitidis is considered to be a harmless colonizer of the airways of cystic fibrosis (CF) patients. The aim of this study was to establish the recovery rate of E. dermatitidis in respiratory specimens from CF patients, transplant recipients, and subjects with other respiratory disorders in Sweden. Second, we wished to determine if particular clinical traits were associated with E. dermatitidis colonization of the airways and the antifungal susceptibility profiles of Exophiala strains. Sputum and bronchoalveolar lavage samples (n = 492) derived from 275 patients were investigated. E. dermatitidis was isolated in respiratory specimens from 19% (18/97) of the CF patients but in none of the other patient categories. All isolates were recovered after 6 to 25 days of incubation on erythritol-chloramphenicol agar (ECA) medium. Morphological and genetic analyses confirmed species identity. Pancreatic insufficiency was positively associated with the presence of E. dermatitidis in sputum samples (P = 0.0198). Antifungal susceptibility tests demonstrated that voriconazole and posaconazole had the lowest MICs against E. dermatitidis. In conclusion, E. dermatitidis is a frequent colonizer of the respiratory tract in CF patients in Sweden and appears to be associated with more advanced disease. Whether E. dermatitidis is pathogenic remains to be elucidated.
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Lass-Flörl C. In vitro susceptibility testing in Aspergillus species: an update. Future Microbiol 2010; 5:789-99. [PMID: 20441550 DOI: 10.2217/fmb.10.34] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aspergillus species are the most common causes of invasive mold infections in immunocompromised patients. The introduction of new antifungal agents and recent reports of resistance emerging during treatment of Aspergillus infections have highlighted the need for in vitro susceptibility testing. Various testing procedures have been proposed, including macro- and micro-dilution, disk diffusion, Etest (AB Biodisk, Sweden) and other commercial tests. Although Aspergillus species are generally susceptible to various compounds, intrinsic and acquired resistance has been documented. Amphotericin B has limited activity against Aspergillus terreus and Aspergillus nidulans. Not surprisingly, continued use of azole-based drugs has the undesirable consequence of elevating the resistance of subsequent isolates from these patients. Several species in the Aspergillus fumigatus complex appear to be resistant to azoles; there is evidence of in vitro and in vivo correlation. Each in vitro susceptibility testing method has its own advantages and disadvantages. Etest is easy to perform and use on a daily basis, yet it is expensive. Disk diffusion is the most attractive alternative method to date, yet we lack sufficient data for aspergilli. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) and the Clinical Laboratory Standard Institute (CLSI) have produced reproducible reference testing methods. This article reviews the available methods for antifungal susceptibility testing in Aspergillus spp. as well as the scant data regarding the clinical implications of in vitro testing.
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Affiliation(s)
- Cornelia Lass-Flörl
- Department of Hygiene, Microbiology & Social Medicine, Division of Hygiene & Clinical Microbiology, Innsbruck Medical University, Fritz Pregl Str 3, 6020 Innsbruck, Austria.
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