Antifungal Susceptibility Profiles and Resistance Mechanisms of Clinical Diutina catenulata Isolates With High MIC Values

Diutina catenulata (Candida catenulata) is an ascomycete yeast species widely used in environmental and industrial research and capable of causing infections in humans and animals. At present, there are only a few studies on D. catenulata, and further research is required for its more in-depth characterization and analysis. Eleven strains of D. catenulata collected from China Hospital Invasive Fungal Surveillance Net (CHIF-NET) and the CHIF-NET North China Program were identified using matrix-assisted laser desorption ionization–time of flight mass spectrometry and internal transcribed spacer sequencing. The antifungal susceptibility of the Diutina catenulata strains was tested using the Clinical and Laboratory Standards Institute broth microdilution method and Sensititre YeastOne™. Furthermore, ERG11 and FKS1 were sequenced to determine any mutations related to azole and echinocandin resistance in D. catenulata. All isolates exhibited low minimum inhibitory concentration (MIC) values for itraconazole (0.06–0.12 μg/ml), posaconazole (0.06–0.12 μg/ml), amphotericin B (0.25–1 μg/ml), and 5-flucytosine (range, <0.06–0.12 μg/ml), whereas four isolates showed high MICs (≥4 μg/ml) for echinocandins. Strains with high MIC values for azoles showed common ERG11 mutations, namely, F126L/K143R. In addition, L139R mutations may be linked to high MICs of fluconazole. Two amino acid alterations reported to correspond to high MIC values of echinocandin, namely, F621I (F641) and S625L (S645), were found in the hot spot 1 region of FKS1. In addition, one new amino acid alteration, I1348S (I1368), was found outside of the FKS1 hot spot 2 region, and its contribution to echinocandin resistance requires future investigation. Diutina catenulata mainly infects patients with a weak immune system, and the high MIC values for various antifungals exhibited by these isolates may represent a challenge to clinical treatment.

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Antifungal Susceptibility Profiles and Drug Resistance Mechanisms of Clinical Lomentospora prolificans Isolates

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00318-20 ◽

2020 ◽

Vol 64 (11) ◽

Cited By ~ 1

Author(s):

Yongqin Wu ◽

Nina Grossman ◽

Marissa Totten ◽

Warda Memon ◽

Anna Fitzgerald ◽

...

Keyword(s):

Amino Acid ◽

Tandem Repeats ◽

Hot Spot ◽

Antifungal Susceptibility ◽

Antifungal Drugs ◽

Upstream Region ◽

Amino Acid Residues ◽

Content Type ◽

Echinocandin Resistance

ABSTRACT Lomentospora prolificans is an opportunistic fungal pathogen with low susceptibility to current antifungal drugs. Here, we tested the in vitro susceptibility of 8 drugs against 42 clinical L. prolificans isolates. All isolates showed high MICs to voriconazole (MIC90>16 μg/ml), itraconazole (MIC90>16 μg/ml), posaconazole (MIC90>16 μg/ml), isavuconazole (MIC90>16 μg/ml), amphotericin B (MIC90>16 μg/ml), and terbinafine (MIC90>64 μg/ml) and high minimum effective concentrations (MECs) to micafungin (MEC90>8 μg/ml), with the exception of miltefosine showing an MIC90 value of 4 μg/ml. We examined six different in vitro drug combinations and found that the combination of voriconazole and terbinafine achieved the most synergistic effort against L. prolificans. We then annotated the L. prolificans whole genome and located its Cyp51 and Fks1 genes. We completely sequenced the two genes to determine if any mutation would be related to azole and echinocandin resistance in L. prolificans. We found no amino acid changes in Cyp51 protein and no tandem repeats in the 5′ upstream region of the Cyp51 gene. However, we identified three intrinsic amino acid residues (G138S, M220I, and T289A) in the Cyp51 protein that were linked to azole resistance. Likewise, two intrinsic amino acid residues (F639Y, W695F) that have reported to confer echinocandin resistance were found in Fks1 hot spot regions. In addition, three new amino acid alterations (D440A, S634R, and H1245R) were found outside Fks1 hot spot regions, and their contributions to echinocandin resistance need future investigation. Overall, our findings support the notion that L. prolificans is intrinsically resistant to azoles and echinocandins.

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Activity of cefepime/zidebactam against MDR Escherichia coli isolates harbouring a novel mechanism of resistance based on four-amino-acid inserts in PBP3

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkaa353 ◽

2020 ◽

Vol 75 (12) ◽

pp. 3563-3567 ◽

Cited By ~ 1

Author(s):

Sachin S Bhagwat ◽

Periasamy Hariharan ◽

Prashant R Joshi ◽

Snehal R Palwe ◽

Rahul Shrivastava ◽

...

Keyword(s):

Escherichia Coli ◽

Amino Acid ◽

Tertiary Care ◽

Resistance Mechanism ◽

Resistance Mechanisms ◽

Care Hospital ◽

E Coli ◽

Microdilution Method ◽

Broth Microdilution Method

Abstract Background Recent reports reveal the emergence of Escherichia coli isolates harbouring a novel resistance mechanism based on four-amino-acid inserts in PBP3. These organisms concomitantly expressed ESBLs or/and serine-/metallo-carbapenemases and were phenotypically detected by elevated aztreonam/avibactam MICs. Objectives The in vitro activities of the investigational antibiotic cefepime/zidebactam and approved antibiotics (ceftazidime/avibactam, ceftolozane/tazobactam, imipenem/relebactam and others) were determined against E. coli isolates harbouring four-amino-acid inserts in PBP3. Methods Whole-genome sequenced E. coli isolates (n = 89) collected from a large tertiary care hospital in Southern India (n = 64) and from 12 tertiary care hospitals located across India (n = 25) during 2016–18, showing aztreonam/avibactam MICs ≥1 mg/L (≥4 times the aztreonam epidemiological cut-off) were included in this study. The MICs of antibiotics were determined using the reference broth microdilution method. Results Four-amino-acid inserts [YRIK (n = 30) and YRIN (n = 53)] were found in 83/89 isolates. Among 83 isolates, 65 carried carbapenemase genes [blaNDM (n = 39), blaOXA-48-like (n = 11) and blaNDM + blaOXA-48-like (n = 15)] and 18 isolates produced ESBLs/class C β-lactamases only. At least 16 unique STs were noted. Cefepime/zidebactam demonstrated potent activity, with all isolates inhibited at ≤1 mg/L. Comparator antibiotics including ceftazidime/avibactam and imipenem/relebactam showed limited activities. Conclusions E. coli isolates concurrently harbouring four-amino-acid inserts in PBP3 and NDM are an emerging therapeutic challenge. Assisted by the PBP2-binding action of zidebactam, the cefepime/zidebactam combination overcomes both target modification (PBP3 insert)- and carbapenemase (NDM)-mediated resistance mechanisms in E. coli.

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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)

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01730-10 ◽

2011 ◽

Vol 55 (6) ◽

pp. 2855-2859 ◽

Cited By ~ 63

Author(s):

A. Espinel-Ingroff ◽

A. Fothergill ◽

J. Fuller ◽

E. Johnson ◽

T. Pelaez ◽

...

Keyword(s):

Antifungal Susceptibility ◽

Acquired Resistance ◽

The United States ◽

Resistance Mechanisms ◽

Broth Microdilution ◽

Wild Type ◽

Content Type ◽

Microdilution Method ◽

Cutoff Values ◽

Broth Microdilution Method

ABSTRACTClinical breakpoints have not been established for mold testing. Epidemiologic cutoff values (ECVs) are available for sixAspergillusspp. 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 sixAspergillusspp. and caspofungin. The number of available isolates was as follows: 1,691A. fumigatus, 432A. flavus, 192A. nidulans, 440A. niger, 385A. terreus, and 75A. versicolorisolates. 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 forA. fumigatus0.5 and 1,A. flavus0.25 and 0.5,A. nidulans0.5 and 0.5,A. niger0.25 and 0.25,A. terreus0.25 and 0.5, andA. versicolor0.25 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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Trends in Antifungal Drug Susceptibility of Cryptococcus neoformans Isolates Obtained through Population-Based Surveillance in South Africa in 2002-2003 and 2007-2008

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00048-11 ◽

2011 ◽

Vol 55 (6) ◽

pp. 2606-2611 ◽

Cited By ~ 43

Author(s):

Nelesh P. Govender ◽

Jaymati Patel ◽

Marelize van Wyk ◽

Tom M. Chiller ◽

Shawn R. Lockhart ◽

...

Keyword(s):

South Africa ◽

Cryptococcus Neoformans ◽

Amphotericin B ◽

Fungal Infections ◽

Antifungal Susceptibility ◽

Drug Susceptibility ◽

Population Based ◽

Content Type ◽

Microdilution Method ◽

Broth Microdilution Method

ABSTRACTCryptococcus neoformansis the most common cause of meningitis among adult South Africans with HIV infection/AIDS. Widespread use of fluconazole for treatment of cryptococcal meningitis and other HIV-associated opportunistic fungal infections in South Africa may lead to the emergence of isolates with reduced fluconazole susceptibility. MIC testing using a reference broth microdilution method was used to determine if isolates with reduced susceptibility to fluconazole or amphotericin B had emerged among cases of incident disease. Incident isolates were tested from two surveillance periods (2002-2003 and 2007-2008) when population-based surveillance was conducted in Gauteng Province, South Africa. These isolates were also tested for susceptibility to flucytosine, itraconazole, voriconazole, and posaconazole. Serially collected isolate pairs from cases at several large South African hospitals were also tested for susceptibility to fluconazole. Of the 487 incident isolates tested, only 3 (0.6%) demonstrated a fluconazole MIC of ≥16 μg/ml; all of these isolates were from 2002-2003. All incident isolates were inhibited by very low concentrations of amphotericin B and exhibited very low MICs to voriconazole and posaconazole. Of 67 cases with serially collected isolate pairs, only 1 case was detected where the isolate collected more than 30 days later had a fluconazole MIC value significantly higher than the MIC of the corresponding incident isolate. Although routine antifungal susceptibility testing of incident isolates is not currently recommended in clinical settings, it is still clearly important for public health to periodically monitor for the emergence of resistance.

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Susceptibility of Filamentous Fungi to Voriconazole in Malaysia Tested by Sensititre YeastOne and CLSI Microdilution Methods

10.21203/rs.3.rs-199013/v1 ◽

2021 ◽

Author(s):

Xue Ting Tan ◽

Stephanie Jane Ginsapu ◽

Fairuz binti Amran ◽

Salina binti Mohamed Sukur ◽

Surianti binti Shukor

Keyword(s):

Filamentous Fungi ◽

Susceptibility Testing ◽

Rhizopus Oryzae ◽

Antifungal Susceptibility ◽

Sporothrix Schenckii ◽

Rank Test ◽

Broth Microdilution ◽

Syncephalastrum Racemosum ◽

Microdilution Method ◽

Broth Microdilution Method

Abstract Background: Voriconazole is a trizaole antifungal to treat fungal infection. In this study, the susceptibility pattern of voriconazole against filamentous fungi was studied using Sensititre® YeastOne and Clinical & Laboratory Standards Institute (CLSI) M38 broth microdilution method. Methods: The suspected cultures of Aspergillus niger, A. flavus, A. fumigatus, A. versicolor, A. sydowii, A. calidoutus, A. creber, A. ochraceopetaliformis, A. tamarii, Fusarium solani, F. longipes, F. falciferus, F. keratoplasticum, Rhizopus oryzae, R. delemar, R. arrhizus, Mucor sp., Poitrasia circinans, Syncephalastrum racemosum and Sporothrix schenckii were received from hospitals. Their identification had been confirmed in our lab and susceptibility tests were performed using Sensititre® YeastOne and CLSI M38 broth microdilution method. The significant differences between two methods were calculated using Wilcoxon Sign Rank test.Results: Mean of the minimum inhibitory concentrations (MIC) for Aspergillus spp. and Fusarium were within 0.25 μg/mL-2.00 μg/mL by two methods except A. calidoutus, F. solani and F. keratoplasticum. Moreover, mean of MIC for S. schenkii were around 3.00 μg/mL by two methods. In contrast, mean of MIC for Rhizopus spp., Mucor sp., P. circinans and S. racemosum were ≥6.00 μg/mL by two methods. Generally, the MIC obtained by Sensititre YeastOne was one two-fold increase or decrease compared with the results obtained by CLSI method. The overall agreement between Sensititre YeastOne and CLSI methods to test susceptibility testing of voricaonazole was more than 70% except A. sydowii. The significant differences between two methods were significant when tested on A. niger, A. flavus, A. fumigatus, A. versicolor, A. sydowii, F. solani and S. schenkii. Conclusions: In conclusion, Sensititre YeastOne method appears to be an alternative procedure for antifungal susceptibility testing for some Malaysian moulds.

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Flow Cytometry Antifungal Susceptibility Testing of Pathogenic Yeasts other than Candida albicans and Comparison with the NCCLS Broth Microdilution Test

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.44.10.2752-2758.2000 ◽

2000 ◽

Vol 44 (10) ◽

pp. 2752-2758 ◽

Cited By ~ 44

Author(s):

Rama Ramani ◽

Vishnu Chaturvedi

Keyword(s):

Flow Cytometry ◽

Candida Albicans ◽

Amphotericin B ◽

Susceptibility Testing ◽

Antifungal Susceptibility ◽

Antifungal Susceptibility Testing ◽

Broth Microdilution ◽

Nitrogen Base ◽

Microdilution Method ◽

Broth Microdilution Method

ABSTRACT Candida species other than Candida albicansfrequently cause nosocomial infections in immunocompromised patients. Some of these pathogens have either variable susceptibility patterns or intrinsic resistance against common azoles. The availability of a rapid and reproducible susceptibility-testing method is likely to help in the selection of an appropriate regimen for therapy. A flow cytometry (FC) method was used in the present study for susceptibility testing ofCandida glabrata, Candida guilliermondii,Candida krusei, Candida lusitaniae,Candida parapsilosis, Candida tropicalis, andCryptococcus neoformans based on accumulation of the DNA binding dye propidium iodide (PI). The results were compared with MIC results obtained for amphotericin B and fluconazole using the NCCLS broth microdilution method (M27-A). For FC, the yeast inoculum was prepared spectrophotometrically, the drugs were diluted in either RPMI 1640 or yeast nitrogen base containing 1% dextrose, and yeast samples and drug dilutions were incubated with amphotericin B and fluconazole, respectively, for 4 to 6 h. Sodium deoxycholate and PI were added at the end of incubation, and fluorescence was measured with a FACScan flow cytometer (Becton Dickinson). The lowest drug concentration that showed a 50% increase in mean channel fluorescence compared to that of the growth control was designated the MIC. All tests were repeated once. The MICs obtained by FC for all yeast isolates except C. lusitaniae were in very good agreement (within 1 dilution) of the results of the NCCLS broth microdilution method. Paired ttest values were not statistically significant (P = 0.377 for amphotericin B; P = 0.383 for fluconazole). Exceptionally, C. lusitaniae isolates showed higher MICs (2 dilutions or more) than in the corresponding NCCLS broth microdilution method for amphotericin B. Overall, FC antifungal susceptibility testing provided rapid, reproducible results that were statistically comparable to those obtained with the NCCLS method.

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Evaluation of a Modified EUCAST Fragmented-Mycelium Inoculum Method forIn VitroSusceptibility Testing of Dermatophytes and the Activity of Novel Antifungal Agents

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04381-14 ◽

2015 ◽

Vol 59 (6) ◽

pp. 3675-3682 ◽

Cited By ~ 4

Author(s):

B. Risslegger ◽

C. Lass-Flörl ◽

G. Blum ◽

M. Lackner

Keyword(s):

Antifungal Agents ◽

Susceptibility Testing ◽

Preparation Method ◽

Antifungal Susceptibility ◽

Broth Microdilution ◽

Microdilution Method ◽

Broth Microdilution Method ◽

Inoculum Preparation ◽

Minimal Effective Concentration

ABSTRACTFor antifungal susceptibility testing of nonsporulating or poorly sporulating dermatophytes, a fragmented-mycelium inoculum preparation method was established and compared to broth microdilution testing according to CLSI and EUCAST guidelines. Moreover, thein vitroactivity of new antifungal agents against dermatophytes was evaluated. Agreement between the mycelial inoculum method and the CLSI broth microdilution method was high (93% to 100%). Echinocandins (minimal effective concentration [MEC], ≤0.5 mg/liter) and posaconazole (MIC, ≤3.00 mg/liter) showed good activity against all tested dermatophytes.

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Evaluation of semisolid agar method for antifungal susceptibility test of T. rubrum

Bangabandhu Sheikh Mujib Medical University Journal ◽

10.3329/bsmmuj.v7i1.29140 ◽

2016 ◽

Vol 7 (1) ◽

pp. 11

Author(s):

Sultana Razia ◽

Shahida Anwar ◽

Md. Ruhul Amin Miah ◽

Najmun Nahar ◽

Ripon Barua

Keyword(s):

Antifungal Agents ◽

Antifungal Susceptibility ◽

Antifungal Drugs ◽

Test Method ◽

Susceptibility Test ◽

Broth Microdilution ◽

Microdilution Method ◽

Broth Microdilution Method ◽

Antifungal Susceptibility Test ◽

Mic Value

Background: With increasing fungal disease many newer antifungal drugs are available with different spectrum of activity. Antifungal susceptibility test will help clinicians for selection of effective drug and thereby treatment of patient. Objective: The study was undertaken to perform a simple screening drug susceptibility test of T. rnbrum by Semi Solid Agar Antifungal Susceptibility (SAAS) Method: Perfonnance of susceptibility method was assessed by comparing the MICs of three commonly prescribed antifungal agents namely- tluconazole (FCZ), itraconazole (ITZ) and terbinafine (TER) to the CLSI (Clinical and Laboratory Standard Institute) recommended M-38, a broth microdilution method. Results: In SAAS method, among twenty nine T. rubrum, twenty five (86.2%) were susceptible (MIC range 0.5-64 µg/ml) to Fluconazole (FCZ) and four (13.7%) were resistant (MIC value >64 µg/ml). In broth microdilution method, among twenty nine T. rubrum, twenty six (89.6%) were susceptible (MIC range 0.3-64 µg/ml) to FCZ and three (10.3%) were resistant (MIC value >64 µg/ml). In case of both ITZ and TER, all were susceptible (MIC range 0.3-64 µg/ml) to both methods. The SAAS method demonstrated the susceptibility pattern of T. rubrum against FCZ, ITZ and TER usually within 72 to 96 hours after organism isolation and results were concordance with the results of CLSI broth microdilution method. Conclusion: Though it is a newer method with proper standardization of the test method, SAAS method is simple and easily applicable screening method for susceptibility testing of antifungal agents against dermatophytes in any microbiology laboratories.

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Antifungal Susceptibility Testing of Malassezia spp. with an Optimized Colorimetric Broth Microdilution Method

Journal of Clinical Microbiology ◽

10.1128/jcm.00338-17 ◽

2017 ◽

Vol 55 (6) ◽

pp. 1883-1893 ◽

Cited By ~ 22

Author(s):

Cheryl Leong ◽

Antonino Buttafuoco ◽

Martin Glatz ◽

Philipp P. Bosshard

Keyword(s):

Susceptibility Testing ◽

Skin Diseases ◽

Antifungal Susceptibility ◽

Drug Susceptibility ◽

Drug Susceptibility Testing ◽

Broth Microdilution ◽

Content Type ◽

Microdilution Method ◽

Broth Microdilution Method ◽

Colorimetric Indicator

ABSTRACTMalasseziais a genus of lipid-dependent yeasts. It is associated with common skin diseases such as pityriasis versicolor and atopic dermatitis and can cause systemic infections in immunocompromised individuals. Owing to the slow growth and lipid requirements of these fastidious yeasts, convenient and reliable antifungal drug susceptibility testing assays forMalasseziaspp. are not widely available. Therefore, we optimized a broth microdilution assay for the testing ofMalasseziathat is based on the CLSI and EUCAST assays forCandidaand other yeasts. The addition of ingredients such as lipids and esculin provided a broth medium formulation that enabled the growth of allMalasseziaspp. and could be read, with the colorimetric indicator resazurin, by visual and fluorescence readings. We tested the susceptibility of 52 strains of 13Malasseziaspecies to 11 commonly used antifungals. MIC values determined by visual readings were in good agreement with MIC values determined by fluorescence readings. The lowest MICs were found for the azoles itraconazole, posaconazole, and voriconazole, with MIC90values of 0.03 to 1.0 μg/ml, 0.06 to 0.5 μg/ml, and 0.03 to 2.0 μg/ml, respectively. AllMalasseziaspp. were resistant to echinocandins and griseofulvin. SomeMalasseziaspp. also showed high MIC values for ketoconazole, which is the most widely recommended topical antifungal to treatMalasseziaskin infections. In summary, our assay enables the fast and reliable susceptibility testing ofMalasseziaspp. with a large panel of different antifungals.

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Molecular Analysis of Resistance and Detection of Non-Wild-Type Strains Using Etest Epidemiological Cutoff Values for Amphotericin B and Echinocandins for Bloodstream Candida Infections from a Tertiary Hospital in Qatar

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00214-18 ◽

2018 ◽

Vol 62 (9) ◽

Cited By ~ 4

Author(s):

Saad J. Taj-Aldeen ◽

Husam Salah ◽

Winder B. Perez ◽

Muna Almaslamani ◽

Mary Motyl ◽

...

Keyword(s):

Amphotericin B ◽

Hot Spot ◽

Antifungal Susceptibility ◽

Tertiary Hospital ◽

Wild Type ◽

Content Type ◽

Cutoff Values ◽

Echinocandin Resistance ◽

Candida Infections ◽

Type Strains

ABSTRACT A total of 301 Candida bloodstream isolates collected from 289 patients over 5 years at a tertiary hospital in Qatar were evaluated. Out of all Candida infections, 53% were diagnosed in patients admitted to the intensive care units. Steady increases in non-albicans Candida species were reported from 2009 to 2014 (30.2% for Candida albicans versus 69.8% for the other Candida species). Etest antifungal susceptibility testing was performed on all recovered clinical isolates to determine echinocandin (micafungin and anidulafungin) and amphotericin B susceptibilities and assess non-wild-type (non-WT) strains (strains for which MICs were above the epidemiological cutoff values). DNA sequence analysis was performed on all isolates to assess the presence of FKS mutations, which confer echinocandin resistance in Candida species. A total of 3.9% of isolates (12/301) among strains of C. albicans and C. orthopsilosis contained FKS hot spot mutations, including heterozygous mutations in FKS1. For C. tropicalis, the Etest appeared to overestimate strains non-WT for micafungin, anidulafungin, and amphotericin B, as 14%, 11%, and 35% of strains, respectively, had values above the epidemiological cutoff value. However, no FKS mutations were identified in this species. For all other species, micafungin best reported the echinocandin non-WT strains relative to the FKS genotype, as anidulafungin tended to overestimate non-wild-type strains. Besides C. tropicalis, few strains were classified as non-WT for amphotericin B.

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