Terbinafine resistance in Trichophyton mentagrophytes and Trichophyton rubrum in the Czech Republic: A prospective multicentric study

BACKGROUND

Terbinafine, an allylamine antifungal, is crucial for treating dermatophytosis by inhibiting squalene epoxidase (SQLE) in the ergosterol biosynthetic pathway. However, resistance is emerging, particularly in India and Southeast Asia, but reports of resistance spread worldwide. Despite this, comprehensive studies on terbinafine resistance in Trichophyton are still limited.

OBJECTIVES

This research aimed to determine the prevalence of terbinafine resistance in the Czech Republic, with a focus on Trichophyton rubrum and Trichophyton mentagrophytes, and investigate the underlying molecular mechanisms.

PATIENTS/METHODS

A total of 514 clinical strains of T. rubrum and 240 T. mentagrophytes collected from four Czech clinical institutions were screened for terbinafine resistance. Molecular investigations included DNA sequencing, specifically the ITS rDNA region and SQLE gene, as well as antifungal susceptibility testing following EUCAST guidelines.

RESULTS

While no resistance was observed in T. rubrum, 2.5% of T. mentagrophytes strains exhibited resistance, marked by the F397L mutation in SQLE. Notably, resistance surged from 1.2% in 2019 to 9.3% in 2020 but reverted to 0% in 2021. All resistant strains were identified as T. mentagrophytes var. indotineae. Resistant strains exhibited high MICs for terbinafine (≥4 mg L-1 ) but low MICs to the other seven antifungals tested except for fluconazole.

CONCLUSIONS

This study highlights the emergence of terbinafine-resistant T. mentagrophytes strains in the Czech Republic, with the F397L mutation being pivotal. Due to the relatively low resistance level, the current guidelines for dermatomycosis treatment in the Czech Republic remain effective, but ongoing surveillance is essential for timely adaptations if resistance patterns change.

Siderophore-Based Noninvasive Differentiation of Aspergillus fumigatus Colonization and Invasion in Pulmonary Aspergillosis

Germination from conidia to hyphae and hyphal propagation of Aspergillus fumigatus are the key pathogenic steps in the development of invasive pulmonary aspergillosis (IPA). By applying in vitro observations in a clinical study of 13 patients diagnosed with probable IPA, here, we show that the transition from colonization to the A. fumigatus invasive stage is accompanied by the secretion of triacetylfusarinine C (TafC), triacetylfusarinine B (TafB), and ferricrocin (Fc) siderophores into urine, with strikingly better sensitivity performance than serum sampling. The best-performing index, the TafC/creatinine index, with a median value of 17.2, provided 92.3% detection sensitivity (95% confidence interval [CI], 64.0 to 99.8%) and 100% specificity (95% CI, 84.6 to 100%), i.e., substantially better than the corresponding indications provided by galactomannan (GM) and β-d-glucan (BDG) serology. For the same patient cohort, the serum GM and BDG sensitivities were 46.2 and 76.9%, respectively, and their specificities were 86.4 and 63.6%, respectively. The time-dependent specific appearance of siderophores in the host's urine represents an impactful clinical diagnostic advantage in the early discrimination of invasive aspergillosis from colonization. A favorable concentration of TafC in a clinical specimen distant from a deep infection site enables the noninvasive sampling of patients suffering from IPA. IMPORTANCE The importance of this research lies in the demonstration that siderophore analysis can distinguish between asymptomatic colonization and invasive pulmonary aspergillosis. We found clear associations between phases of fungal development, from conidial germination to the proliferative stage of invasive aspergillosis, and changes in secondary metabolite secretion. The critical extracellular fungal metabolites triacetylfusarinines C and B are produced during the polarized germination or postpolarized growth phase and reflect the morphological status of the proliferating pathogen. False positivity in Aspergillus diagnostics is minimized as mammalian cells do not synthesize Aspergillus siderophore or mycotoxin molecules.

Host-driven subspeciation in the hedgehog fungus, Trichophyton erinacei, an emerging cause of human dermatophytosis

Trichophyton erinacei is a main cause of dermatophytosis in hedgehogs and is increasingly reported from human infections worldwide. This pathogen was originally described in the European hedgehog (Erinaceus europaeus) but is also frequently found in the African four-toed hedgehog (Atelerix albiventris), a popular pet animal worldwide. Little is known about the taxonomy and population genetics of this pathogen despite its increasing importance in clinical practice. Notably, whether there are different populations or even cryptic species associated with different hosts or geographic regions is not known. To answer these questions, we collected 161 isolates, performed phylogenetic and population-genetic analyses, determined mating-type, and characterised morphology and physiology. Multigene phylogeny and microsatellite analysis supported T. erinacei as a monophyletic species, in contrast to highly incongruent single-gene phylogenies. Two main subpopulations, one specific mainly to Atelerix and second to Erinaceus hosts, were identified inside T. erinacei, and slight differences in the size of microconidia and antifungal susceptibilities were observed among them. Although the process of speciation into two lineages is ongoing in T. erinacei, there is still gene flow between these populations. Thus, we present T. erinacei as a single species, with notable intraspecies variability in genotype and phenotype. The data from wild hedgehogs indicated that sexual reproduction in T. erinacei and de novo infection of hedgehogs from soil are probably rare events and that clonal horizontal spread strongly dominates. The molecular typing approach used in this study represents a suitable tool for further epidemiological surveillance of this emerging pathogen in both animals and humans. The results of this study also highlighted the need to use a multigene phylogeny ideally in combination with other independent molecular markers to understand the species boundaries of dermatophytes. Citation: Čmoková A, Kolařík M, Guillot J, et al. 2022. Host-driven subspeciation in the hedgehog fungus, Trichophyton erinacei, an emerging cause of human dermatophytosis. Persoonia 48: 203-218. https://doi.org/10.3767/persoonia.2022.48.06.

Noninvasive Combined Diagnosis and Monitoring of Aspergillus and Pseudomonas Infections: Proof of Concept

In acutely ill patients, particularly in intensive care units or in mixed infections, time to a microbe-specific diagnosis is critical to a successful outcome of therapy. We report the application of evolving technologies involving mass spectrometry to diagnose and monitor a patient’s course. As proof of this concept, we studied five patients and used two rat models of mono-infection and coinfection. We report the noninvasive combined monitoring of Aspergillus fumigatus and Pseudomonas aeruginosa infection. The invasive coinfection was detected by monitoring the fungal triacetylfusarinine C and ferricrocin siderophore levels and the bacterial metabolites pyoverdin E, pyochelin, and 2-heptyl-4-quinolone, studied in the urine, endotracheal aspirate, or breath condensate. The coinfection was monitored by mass spectrometry followed by isotopic data filtering. In the rat infection model, detection indicated 100-fold more siderophores in urine compared to sera, indicating the diagnostic potential of urine sampling. The tools utilized in our studies can now be examined in large clinical series, where we could expect the accuracy and speed of diagnosis to be competitive with conventional methods and provide advantages in unraveling the complexities of mixed infections.

An Outbreak of Trichophyton quinckeanum Zoonotic Infections in the Czech Republic Transmitted from Cats and Dogs

Trichophyton quinckeanum, a zoophilic dermatophyte mostly known as the causative agent of rodent favus, is relatively rarely reported to cause human infections. Indeed, no infections were detected in Czechia between 2012 and 2015 despite routine verification of species identification by ITS rDNA sequencing. By contrast, 25 human and 11 animal cases of infection were documented from December 2016 to December 2020 and the rates tended to grow every following year. Interestingly, most of the cases were reported in the Olomouc region, suggesting a local outbreak. We bring the evidence that human T. quinckeanum infections are most commonly contracted from infected cats or, less frequently, dogs. Although rodents or contaminated soil and environment could be the source of infection to cats and dogs, the occurrence of infections in multiple animals in the same household suggests direct transmission among animals. Confirmation of the identification by molecular methods is highly recommended due to morphological similarity with T. mentagrophytes/T. interdigitale. Antifungal susceptibility testing of isolates to eight antifungals was performed using EUCAST methodology (E.Def 11.0). Among the tested antifungals, terbinafine, amorolfine, ciclopirox and efinaconazole were most potent in vitro and elevated minimum inhibitory concentrations were obtained for fluconazole and ketoconazole.

Rhizoferrin Glycosylation in Rhizopus microsporus

Rhizopus spp. are the most common etiological agents of mucormycosis, causing over 90% mortality in disseminated infections. The diagnosis relies on histopathology, culture, and/or polymerase chain reaction. For the first time, the glycosylation of rhizoferrin (RHF) was described in a Rhizopus microsporus clinical isolate by liquid chromatography and accurate tandem mass spectrometry. The fermentation broth lyophilizate contained 345.3 ± 13.5, 1.2 ± 0.03, and 0.03 ± 0.002 mg/g of RHF, imido-RHF, and bis-imido-RHF, respectively. Despite a considerable RHF secretion rate, we did not obtain conclusive RHF detection from a patient with disseminated mucormycosis caused by the same R. microsporus strain. We hypothesize that parallel antimycotic therapy, RHF biotransformation, and metabolism compromised the analysis. On the other hand, the full profile of posaconazole metabolites was retrieved by our in house software CycloBranch.

[Chromoblastomycosis and phaeohyphomycosis, overlooked fungal diseases]

Dark-pigmented microscopic fungi are worldwide-spread soil saprophytes often found on plant remnants. In chromoblastomycosis, infectious particles of these fungi enter the human body at the site of injury and may cause chronic infection, mainly in tropical and subtropical endemic areas. Chromoblastomycosis is almost exclusively diagnosed in patients with fully functioning immunity, with typically muriform cells present in infected tissue distinguishing this condition from phaeohyphomycosis. Phaeohyphomycosis, a less specific disease caused by dark-pigmented fungi, usually makes tissue necrotize rather than proliferate, involves a broader range of pathogens of the kingdom Fungi and is mainly associated with immune disorders. Chromoblastomycosis is usually a threat to male adults, globally considered an occupational disease affecting farmers, gardeners, loggers, agricultural commodity traders and other workers exposed to contaminated soil or handling materials of plant origin. In the Czech Republic, immunocompetent patients may be at risk of chromoblastomycosis as imported infection. In the past, however, the infection was also rarely documented as autochthonous in the country.

[Chromoblastomycosis and phaeohyphomycosis - pathogenesis and laboratory diagnosis]

Chromoblastomycosis and phaeohyphomycosis are less common fungal infections caused by dark-pigmented fungi. Virulence factors play an important role in the pathogenesis of these diseases. One of these factors, muriform cells, are the most important element for differential diagnosis of chromoblastomycosis and phaeohyphomycosis using clinical samples and various staining techniques. Accurate identification of pathogens causing chromoblastomycosis and phaeohyphomycosis is very important for correct and early antifungal therapy. Therefore, species identification of the etiological agent should be confirmed by sequencing of DNA from the culture. Early diagnosis may be crucial, especially in case of invasive forms of these infections. The diagnosis may be guided by some immunohistochemistry methods and DNA detection using polymerase chain reaction directly from clinical samples seems to be useful for identification of pathogens causing these severe and life-threatening infections.

[Treatment of chromoblastomycosis and phaeohyphomycosis]

Cases of chromoblastomycosis are frequent in certain parts of the world, especially in some developing countries. Clinical manifestations of chromoblastomycosis are typical. To a certain extent, pathogens causing chromoblastomycosis overlap with those causing phaeohyphomycosis. Although cases of phaeohyphomycosis are not very common, they may end fatally. Therefore early management of these life-threatening infections is rather important. Targeted antifungal therapy and surgery are effective in combating these infections. Recently, several triazole antifungals such as posaconazole and isavuconazole have been available to treat even the most severe cases. Prevention of the infection should be aimed at reducing the risk of subcutaneous trauma, particularly in persons in contact with potential sources of infection such as wood materials important from endemic areas.

[Cryptic Aspergillus species - a case report of chronic cavitary pulmonary Aspergillus lentulus infection in a heart transplant recipient]

Cryptic species within the section Fumigati, that is Aspergillus fumigatus-like species, are increasingly reported in the literature as causative agents of invasive aspergillosis (IA) in both humans and animals. Their detection and proper identification are important, but even more important is to determine the susceptibility profile (minimum inhibitory concentrations, MICs) of the isolate to antifungals using appropriate methods. Cryptic species often demonstrate elevated MICs to drugs recommended for IA therapy such as voriconazole or amphotericin B. Presented is a case of pulmonary aspergillosis in a 63-year-old male heart transplant recipient. Aspergillus lentulus with reduced susceptibility to voriconazole and amphotericin B was identified as the causative agent of the infection using culture and DNA sequencing. Susceptibility to antifungals was confirmed by the standard EUCAST-AFST methods. Based on MIC values obtained in vitro, therapy was switched from voriconazole to posaconazole with excellent clinical effects. To the best of our knowledge, this is the first reported case of A. lentulus infection treated with posaconazole and, moreover, a successful one.

Presepsin in the diagnostics of sepsis

Sepsis remains one of the most common causes of death worldwide. It is caused by a complex of inadequate host responses to infection. It is also often difficult to distinguish sepsis from a non-infectious cause of systemic inflammatory response syndrome. Early identification of an infectious origin may dramatically help to improve the outcome and reduce mortality. That is the main reason why clinicians need fast, reliable and specific biomarkers for recognition of sepsis. Presepsin (sCD-14ST) is one of promising biomarkers, the level of which increases in response to a microbial infection in the host. As a glycoprotein expressed in the membranes of monocytes and macrophages, CD14 (cluster of differentiation 14) serves especially as a co-receptor of the lipopolysaccharide-lipopolysaccharide binding protein complexes, and activates the inflammatory cascade. Consequently, during the inflammatory reaction, sCD14-ST, known as presepsin, is cleaved away from plasma. The objective of this article is to determine the diagnostic value of presepsin in the diagnostics of sepsis, assessing its severity, and monitoring the effectiveness of therapeutic interventions, and to establish the prognostic value of this biomarker.

Nosocomial candidemia in the Czech Republic in 2012-2015: results of a microbiological multicentre study

  Background: Candidemia is a severe and often life-threatening infection frequently occurring in critically ill patients. During the last decade, new therapeutic and prophylactic strategies influenced (at least in some patient subgroups) the epidemiological situation and the spectrum of causative Candida strains. The present multicentre study aimed to assess the current epidemiological situation of Candida strains causing invasive candidiasis (IC) in patients of tertiary care hospitals in the Czech Republic.

MATERIAL AND METHODS

Clinical and microbiological data on patients with bloodstream yeast isolates collected in 11 tertiary care hospitals in the Czech Republic between 2012 and 2015 were analysed. The incidence of cases and species distribution were assessed by study year, age, and specialty. Moreover, an association with the Candida colonization and presence of toxigenic strains of Clostridium difficile in stool prior to blood culture positivity was analysed. For some of the strains, minimum inhibitory concentrations (MICs) of systemic antifungals were determined using standard methods.

RESULTS

A total of 886 episodes of candidemia (921 yeast strains) were identified during the study period. The overall incidence per 1000 admissions was 0.40 (range 0.21-1.22 depending on the hospital). Almost half of the isolates belonged to the species Candida albicans (49.7 %), followed by Candida glabrata (15.3 %) and Candida parapsilosis (11.2 %). Non-albicans species of Candida significantly predominated in oncology wards (71.6 %) as compared to surgery (40.4 %) or internal medicine (52.0 %) departments. More than 70.0 % of patients stayed in intensive care units at the time of positive culture; in 65.0 % of patients, colonization with the same yeast species preceded blood culture positivity. In only 5.1 % of all patients, the previous presence of toxigenic strains of Clostridium difficile in stool was found. Fifty-six of the 921 yeast strains were tested for antifungal susceptibility, with an increase in MICs to azoles being observed for C. glabrata.

CONCLUSION

The incidence of candidemia in the Czech Republic did not vary significantly between 2012 and 2015, and C. glabrata was the second most common yeast species after C. albicans isolated from blood.

[Invasive candidiasis in selected heamatology departments in the Czech Republic and Slovakia - microbiological results of the CAN CELL project]

BACKGROUND

The aim of our study was to analyze the spectrum and characteristic of invasive candidiasis in selected haematological departments in the Czech and Slovak Republics, and to compare minimum inhibitory concentrations (MIC) of some antifungal agents for isolates obtained.

MATERIAL AND METHODS

Between 1 March 2009 and 31 October 2010, Candida strains from clinically important material obtained from patients with haematological malignancies were collected. Each isolate was biochemically identified and tested for in vitro susceptibility to three known echinocandins and amphotericin B and selected azoles using the E-test. Relevant clinical data were collected.

RESULTS

The study included 63 isolates from 61 patients. The most frequently isolated species were C. albicans and C. glabrata (28 % and 19 %, respectively). However, after exclusion of isolates from bronchoalveolar lavage fluid, the percentage changed in favour of C. albicans and C. parapsilosis (25 % and 17 respectively). The MIC data showed a high susceptibility of yeasts to echinocandins and amphotericin B. Ten (16 %) strains were cross-resistant to azoles (mostly C. glabrata).

CONCLUSION

Invasive candidiasis is not frequent infection complication in patients with haematological malignancies in the Czech Republic and Slovakia. Moreover, the spectrum of pathogens was similar to that described in recent international studies. However, identification of susceptible and resistant strains according to MIC could be beneficial for choice of antifungal treatment.