Phenotypic and genotypic characterization of Aspergillus lentulus and Aspergillus fumigatus isolates in a patient with probable invasive aspergillosis

Invasive aspergillosis caused by cryptic species in transplant recipients: A review

The clinical and microbiological characteristics of invasive aspergillosis (IA) caused by cryptic Aspergillus species have not been well-defined in transplant settings. However, IA is among the most common mould infections in solid organ and hematopoietic stem cell transplant recipients. Among 55 causative isolates in the 53 reported cases, Aspergillus calidoustus, A. lentulus, A. tubingensis, and A. udagawae were the four most common causative cryptic Aspergillus species. Newer diagnostic modalities, such as matrix-assisted laser desorption ionization-time of flight mass spectrometry, may help diagnose these cryptic species. Of the 24 cases with detailed clinical information, 13 had antifungal breakthrough infections. The 12-week mortality rates of all 24 cases, 7 cases of A. calidoustus, and 7 cases of A. lentulus were 46%, 43%, and 43%, respectively. Based on antifungal susceptibility profiles obtained from previous studies, an empiric antifungal regimen such as liposomal amphotericin B with or without echinocandin is recommended for A. calidoustus. A combination of an anti-mould azole and liposomal amphotericin B with or without an echinocandin is suggested for A. lentulus and A. udagawae. Additionally, any one of voriconazole, isavuconazole, or posaconazole with or without liposomal amphotericin B with or without an echinocandin is indicated for A. tubingensis. Newer antifungal agents may have more significant activity against Aspergillus cryptic species.

Emerging Aspergillus lentulus infections in India

Here we report first two cases of invasive pulmonary aspergillosis caused by Aspergillus lentulus from India, in non-neutropenic, critically ill patients with chronic obstructive pulmonary disease (COPD).

Aspergillus lentulus: An Under-recognized Cause of Antifungal Drug-Resistant Aspergillosis

Aspergillus lentulus is a drug-resistant species that is phenotypically similar to A. fumigatus. It was discovered as a cause of azole-breakthrough disease, consistent with in vitro resistance. Clinical labs can misidentify the species as fumigatus based on phenotypic typing. We describe 4 recent cases and provide a brief review.

Emergence of Triazole Resistance in Aspergillus spp. in Latin America

Purpose of Review

Azole resistance in Aspergillus spp. is becoming a public health problem worldwide. However, data about this subject is lacking in Latin American countries. This review focuses in the epidemiology and molecular mechanisms of azole resistance in Aspergillus spp. emphasizing in Latin America. Data on Aspergillus fumigatus stands out because it is the most prevalent Aspergillus spp. pathogen.

Recent Findings

Azole resistance in Aspergillus spp. emergence was linked with intensive use of these antifungals both in the clinical setting and in the environment (as pesticides). Reports on azole-resistant A. fumigatus strains are being constantly published in different countries. Molecular mechanisms of resistance mainly involve substitution in the azole target (CYP51A) and/or overexpression of this gene. However, several other non-CYP51A-related mechanisms were described. Moreover, intrinsically resistant cryptic Aspergillus species are starting to be reported as human pathogens.

Summary

After a comprehensive literature review, it is clear that azole resistance in Aspergillus spp. is emerging in Latin America and perhaps it is underestimated. All the main molecular mechanisms of azole resistance were described in patients and/or environmental samples. Moreover, one of the molecular mechanisms was described only in South America. Cryptic intrinsic azole-resistant species are also described.

Characterisation of a clinical isolated Aspergillus lentulus strain using a Galleria mellonella infection model

BACKGROUND

In recent years, the number of invasive aspergillus infection cases caused by Aspergillus lentulus (A. lentulus) has gradually increased and this fungus is usually difficult to distinguish from Aspergillus fumigatus in morphology. All of these presents a great challenge to the treatment of invasive fungal infections caused by A. lentulus. The present study aims to discuss the antifungal resistance, virulence and inflammatory factors' changes after the infection of larvae of A. lentulus separated from patients with chronic obstructive pulmonary disease (COPD) to reflect the host immune response.

METHODS

A. lentulus isolated from COPD patients was identified by morphology and molecular biology, and its drug sensitivity was determined in vitro. Then the virulence factors and inflammatory response related factors of A. lentulus were determined by the model of A. lentulus infecting larvae. These were divided into three groups: A. lentulus standard strain, A. lentulus strain isolated from patients; PBS control. The infection model was formed by injecting the suspension of A. lentulus at a concentration of 1×106 CFU into larvae, in order to determine the (1,3)-β-D-glucan and galactomannan levels, and determine the caspase-1 and TNF-α concentration in Galleria mellonella larvae by RT-PCR.

RESULTS

The results revealed that A. lentulus had good sensitivity to itraconazole, voriconazole and micafungin, while (1,3)-β-D-glucan was negative in the two groups. The level of galactomannan in the two groups was higher than that in the control group, and the difference was statistically significant (P<0.05). However, there was no statistical difference between the standard strain group and patient strain group (P>0.05). After the infection of larvae, caspase-1 and TNF-α in the Galleria mellonella larvae increased in the two groups, and these elevated levels were statistically significant in both groups (P<0.05). However, there was no significant difference between the two groups (P>0.05).

CONCLUSIONS

There is no significant difference in virulence factor and host inflammatory response between A. lentulus isolated from COPD patients and standard strains. Galactomannan has more advantages in the early detection of A. lentulus invasive infection. Furthermore, the caspase-1-mediated inflammasome pathway may be involved in the host immune response to A. lentulus.

Phylogenetic Identification, Diversity, and Richness of Aspergillus from Homes in Havana, Cuba

Aspergillus is one of the most common fungal genera found indoors; it is important because it can cause a wide range of diseases in humans. Aspergillus species identification is based on a combination of morphological, physiological, and molecular methods. However, molecular methodologies have rarely been used for the identification of environmental isolates of Aspergillus in Cuba. Therefore, the objective of this work was to identify the species of the genus Aspergillus obtained from houses in Havana, Cuba, through the construction of phylogeny from a partial sequence of the benA gene region, and to analyze the diversity and richness of Aspergillus in the studied municipalities. Isolates of Aspergillus spp. included in this study presented the typical macro- and micromorphology described for the genus. According to this polyphasic characterization, A. niger, A. flavus, A. welwitschiae, A. heteromorphus, A. sydowii, A. tamarii, A. fumigatus, A. clavatus, and A. tubingensis were the most abundant species. Most of the identified species constitute new records for outdoor and indoor environments in Cuba and contribute to the knowledge of fungal biodiversity in the country. These results constitute an alert for the health authorities of the country, since prolonged exposure of the inhabitants to Aspergillus spores can cause severe persistent asthma, among other diseases.

Trends on Aspergillus Epidemiology-Perspectives from a National Reference Laboratory Surveillance Program

Identification of Aspergillus to species level is important since sibling species may display variable susceptibilities to multiple antifungal drugs and also because correct identification contributes to improve the knowledge of epidemiological studies. Two retrospective laboratory studies were conducted on Aspergillus surveillance at the Portuguese National Mycology Reference Laboratory. The first, covering the period 2017–2018, aimed to study the molecular epidemiology of 256 Aspergillus isolates obtained from patients with respiratory, subcutaneous, or systemic infections and from environmental samples. The second, using our entire collection of clinical and environmental A. fumigatus isolates (N = 337), collected between 2012 and 2019, aimed to determine the frequency of azole-resistant A. fumigatus isolates. Aspergillus fumigatus sensu stricto was the most frequent species in both clinical and environmental samples. Overall, and considering all Aspergillus sections identified, a high frequency of cryptic species was detected, based on beta-tubulin or calmodulin sequencing (37% in clinical and 51% in environmental isolates). Regarding all Fumigati isolates recovered from 2012–2019, the frequency of cryptic species was 5.3% (18/337), with the identification of A. felis (complex), A. lentulus, A. udagawae, A. hiratsukae, and A. oerlinghauensis. To determine the frequency of azole resistance of A. fumigatus, isolates were screened for azole resistance using azole-agars, and 53 possible resistant isolates were tested by the CLSI microdilution reference method. Nine A. fumigatus sensu stricto and six Fumigati cryptic isolates showed high minimal inhibitory concentrations to itraconazole, voriconazole, and/or posaconazole. Real-time PCR to detect cyp51A mutations and sequencing of cyp51A gene and its promoter were performed. The overall frequency of resistance to azoles in A. fumigatus sensu stricto was 3.0%. With this retrospective analysis, we were able to detect one azole-resistant G54R mutant A. fumigatus environmental isolate, collected in 2015. The TR₃₄/L98H mutation, linked to environmental transmission route of azole resistance, was the most frequently detected mutation (N = 4; 1.4%). Our findings underline the demand for correct identification and susceptibility testing of Aspergillus isolates.

The Effects of Different Fungi on the IL-1β Expression in Mouse Dendritic Cells

Background: Invasive fungal infection received more and more attention because of its high mortality, Candida albicans and Aspergillus fumigatus is the most common pathogenic fungus for systematic fungal infection, A. lentulus was isolated and identified recently and named as a sister of A. fumigatus. Objectives: The current study aimed to explore the concentration and time-dependent relationships of the virulence of fungi due to the change in the Interleukin-1 beta (IL-1β) level. Methods: Candida albicans, A. fumigatus, and A. lentulus suspensions with a multiplicity of infection = 0, 1, 5, 10, and 20 units were used to treat mouse dendritic cells. The IL-β level was measured by enzyme-linked immunosorbent assay (ELISA) at 2, 6, 12, 24, and 48 hours after the treatment was administered. Results: The main effects and interactions between the multiplicity of infection, intervention duration, and the dependent variable of IL-1β were significant. Besides, there were statistically significant differences. Only C. albicans and A. lentulus could induce IL-1β 48 hours after administration. Furthermore, the production of IL-1β induced by A. fumigatus was higher than that induced by A. lentulus and C. albicans. Conclusions: This study demonstrated concentration- and time-dependent relationships in IL-1β production by dendritic cells induced by three types of fungi. Candida albicans and A. lentulus exhibited a slow phase-in in vitro inflammation induction. The inflammatory response induced by A. fumigatusin vitro has the characteristics of a short action time and a strong toxic effect. Finally, A. lentulus is less virulent than A. fumigatus, and its inflammation-inducing time is relatively longer.

Development and multicentre validation of an agar-based screening method for echinocandin susceptibility testing of Aspergillus species

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.

Clinical and Microbiological Characterization of Invasive Pulmonary Aspergillosis Caused by Aspergillus lentulus in China

Invasive aspergillosis (IA) due to Aspergillus lentulus is associated with high mortality. In this study, we investigated the clinical and microbiological characteristics of 6 fatal cases of proven or probable IA caused by A. lentulus in China. Underlying immunosuppression, prior antifungal exposure, and intensive care unit (ICU) hospitalization were important risk factors for invasive A. lentulus infection. Phenotypic differences were observed for A. lentulus isolates including slower growth, reduced sporulation, and inability to grow at 48°C, compared with Aspergillus fumigatus complex. ITS sequencing was unable to distinguish A. lentulus from A. fumigatus, but sequencing of the benA, CaM, and rod A loci enabled reliable distinction of these closely related species. Phylogenetic analysis further confirmed that the ITS region had little variation within the Aspergillus section Fumigati while the benA gene offered the highest intraspecific discrimination. Microsatellite typing results revealed that only loci on chromosomes 1, 3, 5, and 6b generated detectable amplicons for identification. All A. lentulus isolates showed in vitro resistance to multiple antifungal drugs including amphotericin B (MIC range 4 to 8 μg/ml), itraconazole (MIC 2 μg/ml), voriconazole (MIC of 4–16 μg/ml), and posaconazole (MIC of 0.5–1 μg/ml). However, MECs for the echinocandin drugs ranged from 0.03–0.25, ≤0.008–0.015, and ≤0.015–0.03 μg/ml for caspofungin, micafungin, and anidulafungin, respectively. A. lentulus is an emerging fungal pathogen in China, causing fatal disease, and clinicians as well as laboratories should be alert to their increasing presence.

Identification of CSP Types and Genotypic Variability of Clinical and Environmental Isolates of Aspergillus fumigatus from Different Geographic Origins

The CSP (cell surface protein) microsatellite marker is useful for typing Aspergillus fumigatus isolates and determining relationships at the subpopulation level because it has shown high discriminatory power. In the present study, 90 A. fumigatus isolates from Mexico (MX), Argentina (AR), France (FR), and Peru (PE) were identified through a phylogenetic analysis using the benA gene fragment and were typed with the CSP microsatellite, and the types were identified using the nomenclature recommended in the literature. Genetic variability was analyzed through haplotype diversity, nucleotide diversity, polymorphic sites, and nucleotide differences between pairs of sequences. The population structure was evaluated using the Tajima's D statistic. No new CSP types were recorded in the MX, FR, and PE isolates, while in the AR isolates, two new CSP types were identified (t25 and t26). The most common CSP types in the studied populations were t01, t02, t03, and t04A; these results are consistent with findings in other countries. In addition, the genetic diversity parameters we obtained revealed that the greatest genetic diversity was found in the MX population, followed by AR and FR. No population structure was identified among the isolates studied.

Invasive pulmonary aspergillosis due to Aspergillus lentulus in an adult patient: A case report and literature review

Aspergillus fumigatus is the commonest cause of pulmonary aspergillosis; however, a recently developed molecular genetic technique identified A. lentulus as a sibling species. Most of the isolates were found in solid organ recipients, often associated with a fatal outcome. Moreover, there is concern that A. lentulus has low susceptibility to multiple antifungal agents. Herein, we report an adult immunocompromised patient with proven invasive pulmonary aspergillosis (IPA) caused by A. lentulus, which was identified through molecular genetic analysis. The patient was diagnosed with IPA by bronchoscopy 3 weeks after initiating systemic corticosteroid therapy for anti-neutrophil cytoplasmic antibody-associated vasculitis. The clinical course of IPA due to A. lentulus showed improvement after treatment with the antifungal agent voriconazole. In summary, we report an adult immunocompromised patient without a history of transplantation who was diagnosed with IPA due to A. lentulus successfully treated with voriconazole, and we also report the findings of a literature review on IPA caused by A. lentulus.

Successful treatment of invasive pulmonary aspergillosis caused by Aspergillus felis, a cryptic species within the Aspergillus section Fumigati: A case report

Aspergillus species are a major cause of life-threatening infections in immunocompromised hosts, and the most common pathogen of invasive aspergillosis is Aspergillus fumigatus. Recently, the development of molecular identification has revealed cryptic Aspergillus species, and A. felis is one such species within the Aspergillus section Fumigati reported in 2013. We describe a case of invasive pulmonary aspergillosis caused by A. felis in a 41-year-old Japanese woman diagnosed with myelodysplastic syndrome. She presented with fever 19 days after undergoing autologous peripheral blood stem cell transplantation and was clinically diagnosed with invasive pulmonary aspergillosis. Bronchoscopy and bronchoalveolar lavage were performed for definitive diagnosis. The β-tubulin genes of the mold isolated from the bronchoalveolar lavage fluid, and sequenced directly from the PCR products using a primer pair were found to have 100% homology with A. felis. We successfully treated the patient with echinocandin following careful susceptibility testing. To the best of our knowledge, this is the first published case reporting the clinical course for diagnosis and successful treatment of invasive aspergillosis by A. felis.

Biodiversity of species of Aspergillus section Fumigati in semi-desert soils in Argentina

The distribution of Aspergillus species in soil has been widely studied all over the world. The aim of this study was the phenotypic and genotypic characterization of species Aspergillus belonging to section Fumigati present in soils from two Argentinian semi-desert areas having different geological conditions. Altogether, 23 isolates belonging to Aspergillus section Fumigati were recovered and identified using a polyphasic approach including phenotypic and molecular identifications. Aspergillus fumigatus sensu stricto and Aspergillus fumigatiaffinis had the highest frequency, of occurrence while isolates closely related to Aspergillus udagawae and Aspergillus felis were rarely observed. A. fumigatiaffinis and isolates closer to A. udagawae were isolated for the first time from Argentinian soils and this is the first report on the occurrence of species belonging to the A. felis clade in South America. Recent scientific interests in biodiversity, as well as the increasing importance of aspergilli as causative agents of human and animal diseases increase the need to understand the diversity and occurrence of these fungi in nature.

Interspecies discrimination of A. fumigatus and siblings A. lentulus and A. felis of the Aspergillus section Fumigati using the AsperGenius® assay

The AsperGenius^® assay detects several Aspergillus species and the A. fumigatus Cyp51A mutations TR₃₄/L98H/T289A/Y121F that are associated with azole resistance. We evaluated its contribution in identifying A. lentulus and A. felis, 2 rare but intrinsically azole-resistant sibling species within the Aspergillus section Fumigati. Identification of these species with conventional culture techniques is difficult and time-consuming. The assay was tested on (i) 2 A. lentulus and A. felis strains obtained from biopsy proven invasive aspergillosis and (ii) control A. fumigatus (n=3), A. lentulus (n=6) and A. felis species complex (n=12) strains. The AsperGenius^® resistance PCR did not detect the TR₃₄ target in A. lentulus and A. felis in contrast to A. fumigatus. Melting peaks for L98H and Y121F markers differed and those of the Y121F marker were particularly suitable to discriminate the 3 species. In conclusion, the assay can be used to rapidly discriminate A. fumigatus, A. lentulus and A. felis.

Triazole Resistance in Aspergillus spp.: A Worldwide Problem?

Since the first description of an azole-resistant A. fumigatus strain in 1997, there has been an increasing number of papers describing the emergence of azole resistance. Firstly reported in the USA and soon after in Europe, it has now been described worldwide, challenging the management of human aspergillosis. The main mechanism of resistance is the modification of the azole target enzyme: 14-α sterol demethylase, encoded by the cyp51A gene; although recently, other resistance mechanisms have also been implicated. In addition, a shift in the epidemiology has been noted with other Aspergillus species (mostly azole resistant) increasingly being reported as causative agents of human disease. This paper reviews the current situation of Aspergillus azole resistance and its implications in the clinical setting.

Aspergillus fumigatus-Related Species in Clinical Practice

Aspergillus fumigatus is the main etiologic agent of invasive aspergillosis (IA). Other Aspergillus species belonging to the section Fumigati (A. fumigatus complex) may occasionally be the cause of IA. These strains are often misidentified, as they cannot be distinguished from A. fumigatus by conventional morphological analysis and sequencing methods. This lack of recognition may have important consequences as these A. fumigatus-related species often display some level of intrinsic resistance to azoles and other antifungal drugs. A. lentulus, A. udagawae, A. viridinutans, and A. thermomutatus (Neosartorya pseudofischeri) have been associated with refractory cases of IA. Microbiologists should be able to suspect the presence of these cryptic species behind a putative A. fumigatus isolate on the basis of some simple characteristics, such as defect in sporulation and/or unusual antifungal susceptibility profile. However, definitive species identification requires specific sequencing analyses of the beta-tubulin or calmodulin genes, which are not available in most laboratories. Multiplex PCR assays or matrix-assisted laser desorption ionization - time-of-flight mass spectrometry (MALDI-TOF MS) gave promising results for rapid and accurate distinction between A. fumigatus and other Aspergillus spp. of the section Fumigati in clinical practice. Improved diagnostic procedures and antifungal susceptibility testing may be helpful for the early detection and management of these particular IA cases.

An alternative host model of a mixed fungal infection by azole susceptible and resistant Aspergillus spp strains

Aspergillus fumigatus is the most common mold involved in human infections. However, the number of non-fumigatus species able to cause disease is continuously increasing. Among them, Aspergillus lentulus is reported in hematological and cystic fibrosis patients and in those treated with corticosteroids. A. lentulus differs from A. fumigatus in some clinically relevant aspects such as virulence and antifungal susceptibility, showing high MICs to most antifungals. Previous studies proved that A. lentulus was pathogenic in immunocompromised mice, although the course of the infection was delayed compared to A. fumigatus. These differences could explain why A. lentulus is mostly found in mixed infections with A. fumigatus challenging the diagnosis and treatment. We used the alternative model host Galleria mellonella to compare virulence, host interaction, fungal burden and antifungal response when larvae were infected with A. fumigatus or A. lentulus alone, and with a mixture of both species. A. lentulus was pathogenic in G. mellonella but infected larvae did not respond to therapeutic doses of voriconazole. We were able to simultaneously detect A. fumigatus and A. lentulus by a multiplex Nested Real Time PCR (MN-PCR). Comparative analysis of larvae histological sections showed melanization of both species but presented a different pattern of immune response by haemocytes. Analysis of fungal burden and histology showed that A. lentulus survived in the G. mellonella despite the antifungal treatment in single and mixed infections. We conclude that the simultaneous presence of antifungal susceptible and resistant Aspergillus species would likely complicate the management of these infections.

Characterization and genetic variability of feed-borne and clinical animal/human Aspergillus fumigatus strains using molecular markers

Aspergillus fumigatus, the major etiological agent of human and animal aspergillosis, is a toxigenic fungus largely regarded as a single species by macroscopic and microscopic features. However, molecular studies have demonstrated that several morphologically identified A. fumigatus strains might be genetically distinct. This work was aimed to apply PCR-restriction length fragment polymorphisms (PCR-RFLP) and random amplification of polymorphic DNA (RAPD) molecular markers to characterize a set of feed-borne and clinical A. fumigatus sensu lato strains isolated from Argentina and Brazil and to determine and compare their genetic variability. All A. fumigatus strains had the same band profile and those typical of A. fumigatus sensu stricto positive controls by PCR-RFLP. Moreover, all Argentinian and Brazilian strains typified by RAPD showed similar band patterns to each other and to A. fumigatus sensu stricto reference strains regardless of their isolation source (animal feeds or human/animal clinical cases) and geographic origin. Genetic similarity coefficients ranged from 0.61 to 1.00, but almost all isolates showed 78% of genetic similarly suggesting that genetic variability was found at intraspecific level. Finally, benA sequencing confirmed its identification as A. fumigatus sensu stricto species. These results suggest that A. fumigatus sensu stricto is a predominant species into Aspergillus section Fumigati found in animal environments as well as in human/animal clinical cases, while other species may be rarely isolated. The strains involved in human and animal aspergillosis could come from the environment where this fungus is frequently found. Rural workers and animals would be constantly exposed.

Invasive pulmonary aspergillosis due to Aspergillus lentulus: Successful treatment of a liver transplant patient

We report a patient with severe invasive pulmonary fungal infection caused by Aspergilllus lentulus, which was identified by genetic analysis, following liver transplantation. The patient was initially suspected to have Aspergilllus fumigatus infection, but worsened clinically despite antifungal therapy appropriate for that species. The patient survived after accurate diagnosis, and detailed drug susceptibility testing led to adequate therapy, demonstrating the importance of performing these investigations for severely immunocompromised patients, including organ transplant recipients.

Early invasive pulmonary aspergillosis in a kidney transplant recipient caused by Aspergillus lentulus: first Brazilian report

We report the first Brazilian case of pulmonary invasive aspergillosis caused by Aspergillus lentulus, a new opportunistic Aspergillus species included in the section fumigati that is usually resistant to amphotericin B and azoles.

Aspergillus fumigatus and related species

The genus Aspergillus contains etiologic agents of aspergillosis. The clinical manifestations of the disease range from allergic reaction to invasive pulmonary infection. Among the pathogenic aspergilli, Aspergillus fumigatus is most ubiquitous in the environment and is the major cause of the disease, followed by Aspergillus flavus, Aspergillus niger, Aspergillus terreus, Aspergillus nidulans, and several species in the section Fumigati that morphologically resemble A. fumigatus. Patients that are at risk for acquiring aspergillosis are those with an altered immune system. Early diagnosis, species identification, and adequate antifungal therapy are key elements for treatment of the disease, especially in cases of pulmonary invasive aspergillosis that often advance very rapidly. Incorporating knowledge of the basic biology of Aspergillus species to that of the diseases that they cause is fundamental for further progress in the field.

Treatment of infections by cryptic Aspergillus species

The best treatment for patients with invasive aspergillosis caused by cryptic Aspergillus species remains uncertain, mainly due to the limited clinical data that have been published so far. In face of this limitation, patients should be treated with standard first-line therapy for invasive aspergillosis, with therapy being modified according to in vitro susceptibility testing. In this review, we summarize the importance of cryptic Aspergillus species in modern medicine, including their prevalence, methods for detection and response to antifungal drugs.

A Case Report on Aspergillus lentulus Pneumonia

BACKGROUND

Aspergillus lentulus was described as a new species in 2005 but it was isolated from Turkey for the first time.

CASE REPORT

A. lentulus was isolated as the cause of pneumonia from a patient who had renal transplantation 4 months ago. The patient received immunosuppressive treatment after transplantation. A. lentulus was isolated from his sputum as an agent in pneumonia developed 4 months after the transplantation. Leukocytes, blastospores, and hyphae were seen in both Gram- and Giemsastained smears of the sputum. The isolate was identified by using the Maren A. Klich algorithm and molecular methods and confirmed by the reference laboratory of the CBS Fungal Biodiversity Centre (The Netherlands). In the susceptibility tests of the isolate, minimal inhibitory concentrations for amphotericin B, voriconazole, posaconazole, and caspofungin were found to be 0.5 μg/mL, 0.25 μg/mL, 0.125 μg/mL, and 0.25 μg/mL, respectively. The patient recovered with voriconazole treatment (2×200 mg/day).

CONCLUSION

The use of the molecular tests is important for identification of A. lentulus strains because they are very easily confused with A.fumigatus strains according to phenotypic characteristics.

Aspergillus felis sp. nov., an emerging agent of invasive aspergillosis in humans, cats, and dogs

We describe a novel heterothallic species in Aspergillus section Fumigati, namely A. felis (neosartorya-morph) isolated from three host species with invasive aspergillosis including a human patient with chronic invasive pulmonary aspergillosis, domestic cats with invasive fungal rhinosinusitis and a dog with disseminated invasive aspergillosis. Disease in all host species was often refractory to aggressive antifungal therapeutic regimens. Four other human isolates previously reported as A. viridinutans were identified as A. felis on comparative sequence analysis of the partial β-tubulin and/or calmodulin genes. A. felis is a heterothallic mold with a fully functioning reproductive cycle, as confirmed by mating-type analysis, induction of teleomorphs within 7 to 10 days in vitro and ascospore germination. Phenotypic analyses show that A. felis can be distinguished from the related species A. viridinutans by its ability to grow at 45°C and from A. fumigatus by its inability to grow at 50°C. Itraconazole and voriconazole cross-resistance was common in vitro.

Discovery of a sexual cycle in Aspergillus lentulus, a close relative of A. fumigatus

Aspergillus lentulus was described in 2005 as a new species within the A. fumigatus sensu lato complex. It is an opportunistic human pathogen causing invasive aspergillosis with high mortality rates, and it has been isolated from clinical and environmental sources. The species is morphologically nearly identical to A. fumigatus sensu stricto, and this similarity has resulted in their frequent misidentification. Comparative studies show that A. lentulus has some distinguishing growth features and decreased in vitro susceptibility to several antifungal agents, including amphotericin B and caspofungin. Similar to the once-presumed-asexual A. fumigatus, it has only been known to reproduce mitotically. However, we now show that A. lentulus has a heterothallic sexual breeding system. A PCR-based mating-type diagnostic detected isolates of either the MAT1-1 or MAT1-2 genotype, and examination of 26 worldwide clinical and environmental isolates revealed similar ratios of the two mating types (38% versus 62%, respectively). MAT1-1 and MAT1-2 idiomorph regions were analyzed, revealing the presence of characteristic alpha and high-mobility-group (HMG) domain genes, together with other more unusual features such as a MAT1-2-4 gene. We then demonstrated that A. lentulus possesses a functional sexual cycle with mature cleistothecia, containing heat-resistant ascospores, being produced after 3 weeks of incubation. Recombination was confirmed using molecular markers. However, isolates of A. lentulus failed to cross with highly fertile strains of A. fumigatus, demonstrating reproductive isolation between these sibling species. The discovery of the A. lentulus sexual stage has significant implications for the management of drug resistance and control of invasive aspergillosis associated with this emerging fungal pathogen.

Invasive aspergillosis caused by cryptic Aspergillus species: a report of two consecutive episodes in a patient with leukaemia

We report a case of two consecutive episodes of invasive aspergillosis caused by cryptic Aspergillus species in a patient with leukaemia. A first episode of pulmonary infection was caused by Aspergillus calidoustus and Aspergillus novofumigatus, and the second episode by A. novofumigatus and Aspergillus viridinutans. Fungal isolates were identified to species level using traditional and sequencing-based molecular methods.

Identification of clinical mold isolates by sequence analysis of the internal transcribed spacer region, ribosomal large-subunit D1/D2, and β-tubulin

Background

The identification of molds in clinical laboratories is largely on the basis of phenotypic criteria, the classification of which can be subjective. Recently, molecular methods have been introduced for identification of pathogenic molds in clinical settings. Here, we employed comparative sequence analysis to identify molds.

Methods

A total of 47 clinical mold isolates were used in this study, including Aspergillus and Trichophyton. All isolates were identified by phenotypic properties, such as growth rate, colony morphology, and reproductive structures. PCR and direct sequencing, targeting the internal transcribed spacer (ITS) region, the D1/D2 region of the 28S subunit, and the β-tubulin gene, were performed using primers described previously. Comparative sequence analysis by using the GenBank database was performed with the basic local alignment search tool (BLAST) algorithm.

Results

For Aspergillus, 56% and 67% of the isolates were identified to the species level by using ITS and β-tubulin analysis, respectively. Only D1/D2 analysis was useful for Trichophyton identification, with 100% of isolates being identified to the species level. Performances of ITS and D1/D2 analyses were comparable for species-level identification of molds other than Aspergillus and Trichophyton. In contrast, the efficacy of β-tubulin analysis was limited to genus identification because of the paucity of database information for this gene.

Conclusions

The molecular methods employed in this study were valuable for mold identification, although the different loci used had variable usefulness, according to mold genus. Thus, a tailored approach is recommended when selecting amplification targets for molecular identification of molds.

Role of Aspergillus lentulus 14-α sterol demethylase (Cyp51A) in azole drug susceptibility

Recent studies have demonstrated that some morphologically atypical Aspergillus fumigatus strains are different species belonging to the section Fumigati. Aspergillus lentulus, one of these sibling species, is increasingly reported in patients under corticosteroid treatment. MICs of most antifungals in clinical use are elevated against A. lentulus, and it shows primary resistance to azole drugs. Two A. lentulus cytochrome P450 14-α sterol demethylases, encoded by A. lentulus cyp51A (Alcyp51A) and Alcyp51B genes, were identified. Targeted cyp51A gene knockout in A. lentulus showed that the intrinsic azole resistance of this species is cyp51A dependent. The Δcyp51A strain was morphologically indistinguishable from the A. lentulus wild-type strain, retaining the ability to cause pulmonary disease in neutropenic mice. The heterologous expression of A. lentulus cyp51A was performed in an A. fumigatus cyp51A-deficient strain, confirming that Cyp51A is responsible for the differences in A. lentulus-azole drug interaction.

Comparative proteomic profiles of Aspergillus fumigatus and Aspergillus lentulus strains by surface-enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI-TOF-MS)

BACKGROUND

Surface-enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI-TOF-MS) was applied to analyze the protein profiles in both somatic and metabolic extracts of Aspergillus species. The study was carried out on some Aspergillus species within the Fumigati section (Aspergillus fumigatus wild-types and natural abnormally pigmented mutants, and Aspergillus lentulus). The aim was to validate whether mass spectrometry protein profiles can be used as specific signatures to discriminate different Aspergillus species or even mutants within the same species.

RESULTS

The growth conditions and the SELDI-TOF parameters were determined to generate characteristic protein profiles of somatic and metabolic extracts of Aspergillus fumigatus strains using five different ProteinChips®, eight growth conditions combining two temperatures, two media and two oxygenation conditions. Nine strains were investigated: three wild-types and four natural abnormally pigmented mutant strains of A. fumigatus and two strains of A. lentulus. A total of 242 fungal extracts were prepared. The spectra obtained are protein signatures linked to the physiological states of fungal strains depending on culture conditions. The best resolutions were obtained using the chromatographic surfaces CM10, NP20 and H50 with fractions of fungi grown on modified Sabouraud medium at 37 °C in static condition. Under these conditions, the SELDI-TOF analysis allowed A. fumigatus and A. lentulus strains to be grouped into distinct clusters.

CONCLUSIONS

SELDI-TOF analysis distinguishes A. fumigatus from A. lentulus strains and moreover, permits separate clusters of natural abnormally pigmented A. fumigatus strains to be obtained. In addition, this methodology allowed us to point out fungal components specifically produced by a wild-type strain or natural mutants. It offers attractive potential for further studies of the Aspergillus biology or pathogenesis.

Unusual Aspergillus species in patients with cystic fibrosis

Poorly sporulating Aspergillus isolates from patients with cystic fibrosis (CF) are generally identified in routine procedures as Aspergillus spp. In this study, we identified and characterized 11 isolates belonging to two unusual Aspergillus species of the section Fumigati (A. lentulus and Neosartorya pseudofischeri) recovered from four different patients. Aspergillus lentulus was found occasionally during a 10-year follow-up study of one CF patient colonized by A. fumigatus. Neosartorya pseudofischeri was isolated from three patients followed in different European hospitals. This species was recovered from two sputum samples of one patient, and from four successive samples of the two other patients, suggesting that it may be responsible for chronic colonization. Both species were isolated together with A. fumigatus. Isolates from both species did not grow at 50°C, and DNA sequence analysis, together with further morphological observations permitted identification at the species level. Growth at different temperatures and antifungal susceptibility were also investigated. All the isolates of N. pseudofischeri exhibited a very low susceptibility to voriconazole (VRZ) whereas a very low susceptibility to VRZ and amphotericin B was seen with the A. lentulus isolates.