Exploring treatment and antifungal resistance in an outbreak of tinea caused by Microsporum audouinii.

BACKGROUND: Microsporum audouinii has resurged recently. Infections with the dermatophyte are difficult to treat, which raises the question if we treat M. audouinii infections with the most effective antifungal (AF) agent. OBJECTIVES: The aims of this study was to investigate an outbreak of tinea capitis (TC) in Denmark, address the challenges in outbreak management and to conduct two reviews regarding previous outbreaks and minimal inhibitory concentration (MIC). METHODS: We used Wood's light, culture, direct microscopy, and PCR for screening and antifungal susceptibility testing (AFST) for treatment optimization. We performed two reviews to explore M. audouinii outbreaks and MIC values using broth microdilution method. RESULTS: Of 73 screened individuals, 10 had confirmed M. audouinii infections. Clinical resistance to griseofulvin was observed in 4 (66%) cases. While previous outbreaks showed high griseofulvin efficacy, our study favoured terbinafine, fluconazole and itraconazole in our hard-to-treat cases. AFST guided the choice of AF. Through the literature search, we identified five M. audouinii outbreaks, where differences in management included the use of Wood's light and prophylactic topical AF therapy. Terbinafine MIC values from the literature ranged from 0.002 to 0.125 mg/L. CONCLUSION: Use of Wood's light and preventive measurements were important for limiting infection. The literature lacked MIC data for griseofulvin against M. audouinii, but indicated sensitivity for terbinafine. The clinical efficacy for M. audouinii treatment was contradictory favouring both terbinafine and griseofulvin. AFST could have a key role in the treatment of difficult cases, but lack of standardisation of AFST and MIC breakpoints limits its usefulness.

Otitis externa.

External otitis (EO) is a common and often painful infection in the ear canal. This review provides an overview of the typical presentation, causes, complications, and treatment of EO. The condition is influenced by factors like pH levels, inflammation, and bacterial or fungal invasion. Most common bacteria involved are Pseudomonas aeruginosa and Staphylococcus aureus, and most common fungi are Aspergillus and Candida species. EO can lead to serious complications, such as necrotising EO, which requires prompt medical attention. Treatment involves local care, ear drops, and, in severe cases, systemic antibiotics.

Correction: Astvad et al. Increasing Terbinafine Resistance in Danish Trichophyton Isolates 2019-2020. J. Fungi 2022, 8, 150.

In paragraph four of the discussion in the original article [...].

Disinfection trials with terbinafine-susceptible and terbinafine-resistant dermatophytes.

BACKGROUND: Treatment of tinea pedis and onychomycosis is complicated by high rates of reinfection and the emergence of terbinafine-resistant strains of Trichophyton spp. Effective disinfection of contaminated socks is an important measure. Appropriate washing reduces the risk of reinfection and is paramount in treating tinea pedis and onychomycosis. OBJECTIVES: The aim of this study was to describe the effect of commonplace disinfection methods using socks pieces inoculated with terbinafine-resistant or terbinafine-susceptible isolates of Trichophyton spp. METHODS: Sock pieces were inoculated with seven terbinafine-resistant isolates of Trichophyton spp. with known mutations in the SQLE-gene (T. rubrum (n = 3), T. interdigitale (n = 1) and T. indotineae (n = 3)) and six terbinafine-susceptible isolates of Trichophyton spp. (T. rubrum (n = 3) and T. interdigitale (n = 3)). Methods of disinfection included soaking in a quaternary ammonium (QAC) detergent (0.5, 2 and 24 h), freezing at -20°C (0.5, 12 and 24 h), domestic and steam washing (both at 40°C with detergent). Sock pieces were cultured for 4 weeks following disinfection. The primary end point was no growth at the end of week 4. RESULTS: Soaking in a QAC-detergent for 24 h procured at disinfectant rate of 100% (13/13), whilst soaking in 0.5 and 2 h had a disinfectant rate of 46.2% (6/13) and 84.6% (11/13), respectively. Domestic washing (40°C with detergent) produced a disinfectant rate of 7.7% (1/13). Freezing at -20°C (0.5, 12 and 24 h) and steam washing (40°C with detergent) had no disinfectant properties. CONCLUSIONS: Soaking in a QAC-detergent for 24 h effectively disinfected sock pieces contaminated with dermatophytes.

A Pragmatic Approach to Susceptibility Classification of Yeasts without EUCAST Clinical Breakpoints.

EUCAST has established clinical breakpoints for the six most common Candida species and Cryptococcus neoformans but not for less common yeasts because sufficient evidence is lacking. Consequently, the question "How to interpret the MIC?" for other yeasts often arises. We propose a pragmatic classification for amphotericin B, anidulafungin, fluconazole, and voriconazole MICs against 30 different rare yeasts. This classification takes advantage of MIC data for more than 4000 isolates generated in the EUCAST Development Laboratory for Fungi validated by alignment to published EUCAST MIC data. The classification relies on the following two important assumptions: first, that when isolates are genetically related, pathogenicity and intrinsic susceptibility patterns may be similar; and second, that even if species are not phylogenetically related, the rare yeasts will likely respond to therapy, provided the MIC is comparable to that against wild-type isolates of more prevalent susceptible species because rare yeasts are most likely "rare" due to a lower pathogenicity. In addition, the treatment recommendations available in the current guidelines based on the in vivo efficacy data and clinical experience are taken into consideration. Needless to say, it is of utmost importance (a) to ascertain that the species identification is correct (using MALDI-TOF or sequencing), and (b) to re-test the isolate once or twice to confirm that the MIC is representative for the isolate (because of the inherent variability in MIC determinations). We hope this pragmatic guidance is helpful until evidence-based EUCAST breakpoints can be formally established.

Increasing Terbinafine Resistance in Danish Trichophyton Isolates 2019-2020.

Terbinafine resistance in Trichophyton species has emerged and appears to be increasing. A new EUCAST susceptibility testing method and tentative ECOFFs were recently proposed for Trichophyton. Terbinafine resistance and target gene mutations were detected in 16 Danish isolates in 2013-2018. In this study, samples/isolates submitted for dermatophyte susceptibility testing 2019-2020 were examined. Species identification (ITS sequencing for T. mentagrophytes/T. interdigitale species complex (SC) isolates), EUCAST MICs and squalene epoxidase (SQLE) profiles were obtained. Sixty-three isolates from 59 patients were included. T. rubrum accounted for 81% and T. mentagrophytes/T. interdigitale SC for 19%. Approximately 60% of T. rubrum and T. mentagrophytes/interdigitale SC isolates were terbinafine non-wildtype and/or had known/novel SQLE mutations with possible implications for terbinafine MICs. All infections with terbinafine-resistant T. mentagrophytes/interdigitale SC isolates were caused by Trichophyton indotineae. Compared to 2013-2018, the number of patients with terbinafine-resistant Trichophyton isolates increased. For T. rubrum, this is partly explained by an increase in number of requests for susceptibility testing. Terbinafine-resistant T. indotineae was first detected in 2018, but accounted for 19% of resistance (4 of 21 patients) in 2020. In conclusion, terbinafine resistance is an emerging problem in Denmark. Population based studies are warranted and susceptibility testing is highly relevant in non-responding cases.

Azole resistance in Aspergillus fumigatus. The first 2-year's Data from the Danish National Surveillance Study, 2018-2020.

BACKGROUND: Azole resistance complicates treatment of patients with invasive aspergillosis with an increased mortality. Azole resistance in Aspergillus fumigatus is a growing problem and associated with human and environmental azole use. Denmark has a considerable and highly efficient agricultural sector. Following reports on environmental azole resistance in A. fumigatus from Danish patients, the ministry of health requested a prospective national surveillance of azole-resistant A. fumigatus and particularly that of environmental origin. OBJECTIVES: To present the data from the first 2 years of the surveillance programme. METHODS: Unique isolates regarded as clinically relevant and any A. fumigatus isolated on a preferred weekday (background samples) were included. EUCAST susceptibility testing was performed and azole-resistant isolates underwent cyp51A gene sequencing. RESULTS: The azole resistance prevalence was 6.1% (66/1083) at patient level. The TR34 /L98H prevalence was 3.6% (39/1083) and included the variants TR34 /L98H, TR34 3 /L98H and TR34 /L98H/S297T/F495I. Resistance caused by other Cyp51A variants accounted for 1.3% (14/1083) and included G54R, P216S, F219L, G54W, M220I, M220K, M220R, G432S, G448S and Y121F alterations. Non-Cyp51A-mediated resistance accounted for 1.2% (13/1083). Proportionally, TR34 /L98H, other Cyp51A variants and non-Cyp51A-mediated resistance accounted for 59.1% (39/66), 21.2% (14/66) and 19.7% (13/66), respectively, of all resistance. Azole resistance was detected in all five regions in Denmark, and TR34 /L98H specifically, in four of five regions during the surveillance period. CONCLUSION: The azole resistance prevalence does not lead to a change in the initial treatment of aspergillosis at this point, but causes concern and leads to therapeutic challenges in the affected patients.

Olorofim Susceptibility Testing of 1,423 Danish Mold Isolates Obtained in 2018-2019 Confirms Uniform and Broad-Spectrum Activity.

Olorofim is a novel antifungal drug in phase 2 trials. It has shown promising in vitro activity against various molds, except for Mucorales. Initially, we observed a broad range of EUCAST MICs for Aspergillus fumigatus Here, we explored the MIC variability in more detail and prospectively investigated the susceptibility of contemporary clinical mold isolates, as population data are needed for future epidemiological cutoff (ECOFF) settings. Fifteen A. fumigatus isolates previously found with low/medium/high MICs (≤0.002 to 0.25 mg/liter) were tested repeatedly and EUCAST MICs read in a blinded fashion by three observers. pyrE, encoding the olorofim target enzyme dihydroorotate dehydrogenase (DHODH), was sequenced. A total of 1,423 mold isolates (10 Aspergillus species complexes [including 1,032 A. fumigatus isolates] and 105 other mold/dermatophyte isolates) were examined. Olorofim susceptibility (modal MIC, MIC50, MIC90, and wild-type upper limits [WT-ULs] [species complexes with ≥15 isolates]) was determined and compared to that of four comparators. MICs (mg/liter) were within two 2-fold dilutions (0.016 to 0.03) for 473/476 determinations. The MIC range spanned four dilutions (0.008 to 0.06). No significant pyrE mutations were found. Modal MIC/WT-UL97.5 (mg/liter) values were 0.03/0.06 (A. terreus and A. flavus), 0.06/0.125 (A. fumigatus and Trichophyton rubrum), and 0.06/0.25 (A. niger and A. nidulans). The MIC range for Scedosporium spp. was 0.008 to 0.25. Olorofim susceptibility was similar for azole-resistant and -susceptible isolates of A. fumigatus but reduced for A. montevidensis and A. chevalieri (MICs of >1). With experience, olorofim susceptibility testing is robust. The testing of isolates from our center showed uniform and broad-spectrum activity. Single-center WT-ULs are suggested.

EUCAST Susceptibility Testing of Isavuconazole: MIC Data for Contemporary Clinical Mold and Yeast Isolates.

Isavuconazole is the newest medical azole. We investigated EUCAST MICs for isavuconazole and seven comparators against 1,498 contemporary isolates (2016 to 2017). EUCAST susceptibility testing was performed. Isavuconazole MICs >2 dilution steps above the modal MIC were regarded as non-wild type for species without EUCAST epidemiological cutoff values (ECOFFs). CYP51A sequencing was performed when relevant. Pearson correlation analysis was adopted for comparing activity. Aspergillus accounted for 90% of mold and Candida accounted for 97% of yeast isolates. Thirty (9.3%) Aspergillusfumigatus isolates were classified as resistant, and 10 (3.1%) were classified as non-wild type. Thirteen (4%) were cross-resistant to other mold-active azoles. Target gene alterations were found in 10 (76.9%) isolates, including 4 (30.8%) of environmental origin (TR34/L98H [n = 3] and Trip343/L98H [n = 1]). Six Aspergillusterreus isolates were resistant, including two (17%) with MICs of >2 mg/liter and M217I alterations. Modal MICs/MIC50s (milligrams per liter) against Candida spp. were ≤0.004/≤0.004 for C. albicans and C. dubliniensis, 0.008/0.008 for C. tropicalis, 0.016/0.016 for C. parapsilosis, 0.06/0.06 for C. glabrata, and 0.125/0.125 for C. krusei A non-wild-type phenotype was observed for 6.6% of isolates (C. glabrata [11.8%] and C. tropicalis [12.3%], specifically). All of these isolates were nonsusceptible/non-wild type to fluconazole (96.1%) or voriconazole (86.2%). Low MICs were found for several other species, except Scedosporium apiospermum and Fusarium The best correlation was found between isavuconazole and voriconazole overall but for A. terreus and Mucorales to itraconazole and posaconazole, respectively. Isavuconazole displayed broad in vitro activity. Acquired resistance was infrequent except in A. terreus, C. glabrata, and C. tropicalis and, when present, was associated with cross-resistance to other azoles. Revising the EUCAST breakpoints for A. fumigatus (defining an MIC of 2 mg/liter as intermediate ["I"]) would minimize major errors.

Fluconazole Pharmacokinetics in Galleria mellonella Larvae and Performance Evaluation of a Bioassay Compared to Liquid Chromatography-Tandem Mass Spectrometry for Hemolymph Specimens.

The invertebrate model organism Galleria mellonella can be used to assess the efficacy of treatment of fungal infection. The fluconazole dose best mimicking human exposure during licensed dosing is unknown. We validated a bioassay for fluconazole detection in hemolymph and determined the fluconazole pharmacokinetics and pharmacodynamics in larval hemolymph in order to estimate a humanized dose for future experiments. A bioassay using 4-mm agar wells, 20 µl hemolymph, and the hypersusceptible Candida albicans DSY2621 was established and compared to a validated liquid chromatography-tandem mass spectrometry (LC-MS-MS) method. G. mellonella larvae were injected with fluconazole (5, 10, and 20 mg/kg of larval weight), and hemolymph was harvested for 24 h for pharmacokinetics calculations. The exposure was compared to the human exposure during standard licensed dosing. The bioassay had a linear standard curve between 1 and 20 mg/liter. Accuracy and coefficients of variation (percent) values were below 10%. The Spearman coefficient between assays was 0.94. Fluconazole larval pharmacokinetics followed one-compartment linear kinetics, with the 24-h area under the hemolymph concentration-time curve (AUC24 h) being 93, 173, and 406 mg · h/liter for the three doses compared to 400 mg · h/liter in humans under licensed treatment. In conclusion, a bioassay was validated for fluconazole determination in hemolymph. The pharmacokinetics was linear. An exposure comparable to the human exposure during standard licensed dosing was obtained with 20 mg/kg.

Implementation of Isavuconazole in a Fluorescence-Based High-Performance Liquid Chromatography Kit Allowing Simultaneous Detection of All Four Currently Licensed Mold-Active Triazoles.

Isavuconazole (ISZ) is a newly available broad-spectrum triazole agent recently approved for the treatment of both invasive aspergillosis and mucormycosis. The aim of this study was to develop a simple and reliable method for therapeutic drug monitoring (TDM) of ISZ in human plasma samples. The method involves using a kit from ChromSystems intended for TDM of itraconazole (ITZ), posaconazole (PSZ), and voriconazole (VRZ) in serum/plasma for sample preparation and high-performance liquid chromatography, using fluorescence detection with emission and excitation wavelengths set to 261 and 366 nm, respectively. The assay was linear over the ISZ concentration range of 0.2 to 20.0 mg/liter, using a 0.1-ml sample volume. The inter- and intraday coefficients of variation were all below 3.7%, whereas the accuracies ranged from 95.0 to 106.2% and the mean extraction recovery was 91.9%. In addition, the method worked well using four different Vacutainer types, with six different healthy volunteers and under a number of relevant storage conditions. Finally, the ISZ detection could be seamlessly implemented in the TDM kit for VRZ, PSZ, and ITZ, enabling simultaneous detection of all four triazoles. This method proved to be simple, accurate, precise, and well suited for routine analysis work. It has been implemented in our laboratory for the simultaneous quantitative analysis of ISZ, VRZ, PSZ, and ITZ for TDM and pharmacokinetic research. IMPORTANCE Isavuconazole is a new broad-spectrum triazole agent recently approved for the treatment of both invasive aspergillosis and mucormycosis. Currently, there is no consensus regarding the potential need for TDM of isavuconazole, and no therapeutic window has been defined. However, at the ECIL-6 meeting in 2015, it was advised that TDM is indicated in a number of different settings. In this study, we describe a rapid and validated isocratic HPLC method for fluorescence-based detection and quantification of isavuconazole in human plasma/serum samples. The method is simple and efficient with good accuracy and precision and importantly only requires a small volume of patient plasma/serum. Furthermore, this method is highly sensitive and selective and can be detected simultaneously with the three other triazoles, itraconazole, voriconazole, and posaconazole, without the need for expensive mass spectrometry equipment.

Stepwise emergence of azole, echinocandin and amphotericin B multidrug resistance in vivo in Candida albicans orchestrated by multiple genetic alterations.

OBJECTIVES: The objective of this study was to characterize the underlying molecular mechanisms in consecutive clinical Candida albicans isolates from a single patient displaying stepwise-acquired multidrug resistance. METHODS: Nine clinical isolates (P-1 to P-9) were susceptibility tested by EUCAST EDef 7.2 and Etest. P-4, P-5, P-7, P-8 and P-9 were available for further studies. Relatedness was evaluated by MLST. Additional genes were analysed by sequencing (including FKS1, ERG11, ERG2 and TAC1) and gene expression by quantitative PCR (CDR1, CDR2 and ERG11). UV-spectrophotometry and GC-MS were used for sterol analyses. In vivo virulence was determined in the insect model Galleria mellonella and evaluated by log-rank Mantel-Cox tests. RESULTS: P-1 + P-2 were susceptible, P-3 + P-4 fluconazole resistant, P-5 pan-azole resistant, P-6 + P-7 pan-azole and echinocandin resistant and P-8 + P-9 MDR. MLST supported genetic relatedness among clinical isolates. P-4 harboured four changes in Erg11 (E266D, G307S, G450E and V488I), increased expression of ERG11 and CDR2 and a change in Tac1 (R688Q). P-5, P-7, P-8 and P-9 had an additional change in Erg11 (A61E), increased expression of CDR1, CDR2 and ERG11 (except for P-7) and a different amino acid change in Tac1 (R673L). Echinocandin-resistant isolates harboured the Fks1 S645P alteration. Polyene-resistant P-8 + P-9 lacked ergosterol and harboured a frameshift mutation in ERG2 (F105SfsX23). Virulence was attenuated (but equivalent) in the clinical isolates, but higher than in the azole- and echinocandin-resistant unrelated control strain. CONCLUSIONS: C. albicans demonstrates a diverse capacity to adapt to antifungal exposure. Potentially novel resistance-inducing mutations in TAC1, ERG11 and ERG2 require independent validation.