Species identification and antifungal susceptibility testing of Aspergillus strains isolated from patients with otomycosis in northern China

Pathogenic Aspergillus Strains Identification and Antifungal Susceptibility Analysis of 452 Cases with Otomycosis in Jingzhou, China

OBJECTIVE

To study the distribution of pathogenic Aspergillus strains of otomycosis in central China and the identification of their antifungal sensitivity.

METHODS

We collected external ear canal secretions clinically diagnosed as otomycosis from April 2020 to January 2023 from the Department of Otolaryngology-Head and Neck Surgery in central China. The pathogenic Aspergillus strains were identified through morphological examination and sequencing. The antifungal sensitivity was performed using the broth microdilution method described in the Clinical Laboratory Standard Institute document M38-A3.

RESULTS

In the 452 clinical strains isolated from the external ear canal, 284 were identified as Aspergillus terreus (62.83%), 92 as Aspergillus flavus (20.35%), 55 as Aspergillus niger (12.17%). In antifungal susceptibility tests the MIC of Aspergillus strains to bifonazole and clotrimazole was high,all the MIC90 is > 16 ug/mL. However, most Aspergillus isolates show moderate greatly against terbinafine, itraconazole and voriconazole.

CONCLUSION

A. terreus is the most common pathogenic Aspergillus strain in otomycosis in central China. The selected topical antifungal drugs were bifonazole and clotrimazole; the drug resistance rate was approximately 30%. If the infection is persistent and requires systemic treatment, terbinafine and itraconazole can be used. The resistance of Aspergillus in otomycosis to voriconazole should be screened to avoid the systemic spread of infection in immunocompromised people and poor compliance with treatment. However, the pan-azole-resistant strain of Aspergillus should be monitored, particularly in high-risk patients with otomycosis.

Aspergillus terreus spondylodiscitis following acupuncture and acupotomy in an immunocompetent host: case report and literature review

Aspergillus terreus is a fungus responsible for various infections in human beings; however, spine involvement is uncommon. Herein, we report a case of A. terreus spondylodiscitis following acupuncture and acupotomy in an immunocompetent Chinese patient. Admission lumbar magnetic resonance imaging (MRI) revealed infection at the L4/5 level without significant vertebral destruction. After unsuccessful symptomatic and anti-tuberculosis treatments, A. terreus was identified through culture, microscopy of isolate, histological examination and VITEK system. Intravenous voriconazole was then given; however, the patient's spinal condition deteriorated rapidly, resulting in evident destruction of the L4/5 vertebral bodies. Surgeries including L4/5 intervertebral disc debridement, spinal canal decompression, posterior lumbar interbody fusion (PLIF) with allogeneic fibula ring fusion cages, and posterior pedicle screw fixation were then performed. Imaging findings at one-month and six-month follow-up suggested that the patient was successfully treated. This case highlighted two important points: firstly, although acupuncture and acupotomy are generally regarded as safe conservative treatments for pain management, they can still lead to complications such as fungal spinal infection. Therefore, vigilance is necessary when considering these treatments; secondly, PLIF with allogeneic fibula ring fusion cages may be beneficial for A. terreus spondylodiscitis patients with spinal instability.

Prediction of methicillin-resistant Staphylococcus aureus and carbapenem-resistant Klebsiella pneumoniae from flagged blood cultures by combining rapid Sepsityper MALDI-TOF mass spectrometry with machine learning

This study investigated combination of the Rapid Sepsityper Kit and a machine learning (ML)-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) approach for rapid prediction of methicillin-resistant Staphylococcus aureus (MRSA) and carbapenem-resistant Klebsiella pneumoniae (CRKP) from positive blood culture bottles. The study involved 461 patients with monomicrobial bloodstream infections. Species identification was performed using the conventional MALDI-TOF MS Biotyper system and the Rapid Sepsityper protocol. The data underwent preprocessing steps, and ML models were trained using preprocessed MALDI-TOF data and corresponding labels. The interpretability of the model was enhanced using SHapely Additive exPlanations values to identify significant features. In total, 44 S. aureus isolates comprising 406 MALDI-TOF MS files and 126 K. pneumoniae isolates comprising 1249 MALDI-TOF MS files were evaluated. This study demonstrated the feasibility of predicting MRSA among S. aureus and CRKP among K. pneumoniae isolates using MALDI-TOF MS and Sepsityper. Accuracy, area under the receiver operating characteristic curve, and F1 score for MRSA/methicillin-susceptible S. aureus were 0.875, 0.898 and 0.904, respectively; for CRKP/carbapenem-susceptible K. pneumoniae, these values were 0.766, 0.828 and 0.795, respectively. In conclusion, the novel ML-based MALDI-TOF MS approach enables rapid identification of MRSA and CRKP from flagged blood cultures within 1 h. This enables earlier initiation of targeted antimicrobial therapy, reducing deaths due to sepsis. The favourable performance and reduced turnaround time of this method suggest its potential as a rapid detection strategy in clinical microbiology laboratories, ultimately improving patient outcomes.

Analysis of Airborne Fungal Communities on Pedestrian Bridges in Urban Environments

Airborne fungal spores constitute an important type of bioaerosol and are responsible for a number of negative effects on human health, including respiratory diseases and allergies. We investigated the diversity and concentration of culturable airborne fungi on pedestrian bridges in Tianjin, China, using an HAS-100B air sampler. We compared the airborne fungal communities at the top central area of the selected pedestrian bridges and along the corresponding sidewalk, at ground level. A total of 228 fungal strains belonging to 96 species and 58 genera of Ascomycota (68.86%), Basidiomycota (30.26%), and Mucoromycota (0.88%) were isolated and identified using morphological and molecular analysis. Alternaria was the dominant genus (20.61%), followed by Cladosporium (11.48%), Schizophyllum (6.14%), Sporobolomyces (5.70%), and Sporidiobolus (4.82%). Alternaria alternata was the most frequently occurring fungal species (6.58%), followed by Schizophyllum commune (5.26%), Alternaria sp. (4.82%), Sporobolomyces carnicolor (4.39%), and Cladosporium cladosporioides (3.95%). The recorded fungal concentration ranged from 10 to 180 CFU/m3. Although there was no significant difference in the distribution and abundance of the dominant airborne fungal taxa between the two investigated bridges' sites, numerous species detected with a low percentage of abundance belonging to well-known pathogenic fungal genera, including Alternaria, Aspergillus, Aureobasidium, Cladosporium, Penicillium, and Trichoderma, were exclusively present in one of the two sites. The relative humidity showed a stronger influence compared to the temperature on the diversity and concentration of airborne fungi in the investigated sites. Our results may provide valuable information for air quality monitoring and for assessing human health risks associated with microbial pollution.

Molecular strategy for the direct detection and identification of the most common fungal community in cerumen specimens by multiplex PCR

Introduction. Otomycosis is a superficial fungal infection that is responsible for approximately 9-27 % of otitis externa. However, fungal communities in otomycosis are varied, but Aspergillus spp. and Candida spp. are the most common causes of this infection.Hypothesis Statement. The multiplex PCR assay is postulated to be able to directly detect more than one fungal genus in cerumen specimens.Aim. This study aimed to develop and evaluate the role of the multiplex PCR assay in detecting the most common genus of fungi that cause otomycosis directly from the cerumen specimens.Methodology. To detect Candida and Aspergillus/Penicillium genera, three pairs of primers, including pan-fungal, pan-Candida, and pan-Aspergillus/Penicillium, were used in a multiplex PCR. In order to evaluate the performance and reproducibility of the multiplex PCR. the cerumen of 140 patients suspected of otomycosis were investigated.Results. Pan-Candida and pan-Aspergillus/Penicillium primers were designed to amplify the ITS1-5.8S-ITS2 region and the β-tubulin gene, respectively. In the multiplex PCR assay, 64 (47.40 %) and 118 (87.40 %) specimens were positive with pan-Candida and pan-Aspergillus/Penicillium primers, respectively. Double amplicon bands of Candida and Aspergillus were obtained in 51 (37.77 %) specimens. In the culture method, yeast (n=18, 13.33 %) and mould (n=117, 86.66 %) were isolated from 135 cerumen specimens. The sensitivity, specificity, and positive and negative predictive values of the multiplex PCR assays using culture method results as the gold standard were determined to be 94, 33, 97, and 22 %, respectively.Conclusion. In our study, multiplex PCR assays enabled simultaneous detection of two common genera of the causative agent of otomycosis in a cerumen specimen. Regarding the high sensitivity of the first step of the multiplex PCR assay, this assay may be used for the direct detection of Candida and Aspergillus genera in other clinical specimens.

Aspergillus welwitschiae; a predominant otomycosis agent, new epidemiological and antifungal susceptibility data from Iran

BACKGROUND

Black aspergilli (section Nigri) are predominate etiologic agents of otomycosis, however, there is controversy in the exact differentiation of species. For several decades Aspergillus niger is considered the main otomycosis etiologic agent. Recently calmodulin gene has been accepted as a more suitable gene for the accurate assignment of Aspergillus species. Therefore, it is found that A. welwitschiae and A. tubingensis are the main otomycosis agents based on calmodulin gene sequencing.

AIMS

The objective of the study was to isolate and identify black aspergilli from otomycosis using the calmodulin gene and their susceptibility was evaluated against several antifungals.

METHODS

134 clinically confirmed patients with otomycosis were sampled and specimens were cultured on Sabouraud dextrose agar (SDA) at ambient temperature. Black aspergilli were screened based on colony morphology on SDA and microscopy features and then subjected to sequencing using calmodulin primers. Moreover, antifungal susceptibility for isolates was applied based on CLSI M38 3rd edition.

RESULTS

132 (98.5%) of patients had positive cultures for different species of molds or yeasts. Most of the patients (30.3%) ranged from 31 to 40 years, and 56.1% of them were female. Aspergillus section Nigri was the most prevalent fungal pathogen and of 86 isolates, 60.5% isolates were identified as A. welwitschiae, A. tubingensis, 31 (36.0%), A. niger (sensu stricto), 2 (2.3%), and A. neoniger 1 (1.2%). According to the maximum likelihood method, all isolates of A. tubingensis and one isolate of A. neoniger were included in the A. tubingensis clade. On the other hand, the clade of A. niger/A. welwitschiae contains, all isolates of A. welwitschiae, two A. niger (sensu stricto) isolates, and 36 isolates from other countries. Aspergillus welwitschiae was more sensitive to luliconazole, voriconazole, and amphotericin B compared to A. tubingensis. 78.8% of A. welwitschiae strains were classified as non-wild type to nystatin compared to 35.5% of A. tubingensis. Moreover, 3.2% of A. tubingensis strains were non-wild type against amphotericin B. The isolates of A. tubingensis were more sensitive to itraconazole than A. welwitschiae.

CONCLUSIONS

It is concluded that in contrast, to the previous study A. welwitschiae from section Nigri is the most causative agent of otomycosis followed by A. tubingensis. In addition, the isolates of A. welwitschiae were more sensitive to luliconazole, voriconazole, and amphotericin B compared to A. tubingensis. Whereas, the isolates of A. tubingensis were more sensitive to itraconazole than A. welwitschiae. On the other hand, 78.8% and 35.5% of A. welwitschiae and A. tubingensis strains were classified as a non-wild type against nystatin. Also, 3.2% of A. tubingensis strains were non-wild type against amphotericin B. All A. welwitschiae were included in the A. niger/A. welwitschiae clade, associated with different clinical and environmental species from different countries.

Species distribution and antifungal susceptibility of clinical Aspergillus isolates: A multicentre study in Taiwan, 2016-2020

BACKGROUND

Epidemiological knowledge is important to guide antifungal therapy.

OBJECTIVE

This multicentre study aimed to investigate the species distribution and antifungal susceptibility of Aspergillus isolates in Taiwan.

METHOD

Four hundred and ninety-two clinical Aspergillus isolates, collected during 2016-2020, were identified by calmodulin sequencing and tested for antifungal susceptibility using CLSI M38-A3. The Cyp51A sequences of azole-resistant Aspergillus fumigatus and Aspergillus flavus isolates were analysed.

RESULTS

This collection comprised 30 species from eight Aspergillus sections-Flavi (33.5%), Nigri (26.0%), Fumigati (24.2%), Terrei (10.0%), Nidulantes (5.1%), Circumdati (0.8%), Restricti (0.2%) and Aspergillus (0.2%). Sections Fumigati, Flavi and Terrei were primarily represented by A. fumigatus (99.2%), A. flavus (95.8%) and A. terreus (100%), respectively. Section Nigri comprised nine species, mostly A. welwitschiae (60.2%), A. niger (12.5%), A. brunneoviolaceus (10.9%) and A. tubingensis (10.2%). A. fumigatus (39.6%) and A. flavus (26.4%) predominated among 53 isolates from lower respiratory samples, whereas section Nigri species (46.2%) and A. terreus (29.2%) predominated among 65 isolates from ear samples. Reduced susceptibility to amphotericin B (minimal inhibitory concentration (MIC) > 1 μg/mL) was noted in A. flavus (7.0%), A. terreus (6.1%), A. nidulans and section Circumdati (A. flocculosus, A. subramanianii and A. westerdijkiae) isolates. Acquired azole resistance was observed in seven A. fumigatus (5.9%), all of which carried TR₃₄ /L98H or TR₃₄ /L98H/S297T/F495I mutation, and three A. flavus (1.9%), one of which carried G441S mutation. Reduced susceptibility to itraconazole (MIC >1 μg/mL) was noted in 55.5% of section Nigri isolates, mainly in A. welwitschiae, A. niger and A. tubingensis, whereas A. brunneoviolaceus, A. aculeatinus and A. japonicus were hypersusceptible to azoles. Anidulafungin was active against all isolates except for one isolate.

CONCLUSIONS

This study depicted the molecular epidemiology and species-specific characteristics of Aspergillus in Taiwan, which aids in appropriate antifungal therapy and underlines the need of speciation and susceptibility testing of disease-causing Aspergillus.

Virulence capacity of different Aspergillus species from invasive pulmonary aspergillosis

Introduction

The opportunistic filamentous fungus Aspergillus causes invasive pulmonary aspergillosis (IPA) that often turns into a fatal infection in immunocompromised hosts. However, the virulence capacity of different Aspergillus species and host inflammation induced by different species in IPA are not well understood.

Methods

In the present study, host inflammation, antimicrobial susceptibilities and virulence were compared among clinical Aspergillus strains isolated from IPA patients.

Results

A total of 46 strains were isolated from 45 patients with the invasive infection, of which 35 patients were diagnosed as IPA. Aspergillus flavus was the dominant etiological agent appearing in 25 cases (54.3%). We found that the CRP level and leukocyte counts (elevated neutrophilic granulocytes and monocytes, and reduced lymphocytes) were significantly different in IPA patients when compared with healthy individuals (P < 0.05). Antifungal susceptibilities of these Aspergillus isolates from IPA showed that 91%, 31%, 14%, and 14% were resistant to Fluconazole, Micafungin, Amphotericin B and Terbinafine, respectively. The survival rate of larvae infected by A. flavus was lower than larvae infected by A. niger or A. fumigatus (P < 0.05).

Discussion

Aspergillus flavus was the dominant clinical etiological agent. Given the prevalence of A. flavus in our local clinical settings, we may face greater challenges when treating IPA patients.

Definite therapy of mixed infection alleviates refractory dilemma of adult chronic suppurative otitis media

The characteristics, risk factors, microbial distributions and effective treatment regimens for Chronic suppurative otitis media (CSOM) patients intractable to empirical therapy were analyzed. Adult CSOM patients of China Medical University Hospital from 2018 to 2020 were included. Subjects of refractory and non-refractory groups were investigated for characteristics of age, sex, nation, comorbidities, otomycosis, and associated complications. Risk factors, microbiology distributions, and treatment regimens were analyzed. Twenty-six refractory patients (55.0 ± 17.7 years) and 66 non-refractory patients (54.1 ± 13.7 years) were studied. A significantly higher rate of otomycosis and CSOM complications was observed in refractory group than in non-refractory one (73.1% vs. 36.4%; p = 0.002; 57.7% vs. 10.6%, p < 0.001, respectively). Multivariate analysis revealed atopic diathesis (p = 0.048), otomycosis (p = 0.003) and CSOM complications (p < 0.001) were risk factors of refractory CSOM. Coagulase-negative staphylococci (CoNS) and methicillin-resistant Staphylococcus aureus (MRSA) were the prevailing pathogens. Patients of refractory group tented to have higher rates of mixed infection (42.9%% vs. 23.7%) and significantly more included fungal pathogen (19.0% vs. 2.6%; p = 0.049) than those of non-refractory cohort. Topical treatment of fungus significantly improved outcome of refractory CSOM. Atopic diathesis, otomycosis, and CSOM-associated complications were risk factors of refractory CSOM. Systemic and local treatment to possible drug-resistant pathogens, likely CoNS and fungus, possible improves recalcitrant CSOM. Correspondingly, early identification of CSOM complications, routine culture and susceptibility testing and treatment of resistant bacteria and fungus are key elements to the successful management of adult CSOM.

In Vitro Combination of Terbinafine with Ketoconazole Against Aspergillus Species with Terbinafine High MIC Values Isolated From Otomycosis

Otomycosis is a common mycotic infection of the external auditory canal, and Aspergillus species are one of the most frequent causative agents worldwide. The limited antifungal arsenal, the high toxicity and side effects of antifungal agents, and the growing resistance to the currently available antifungals underscore the need for new therapeutic strategies. The present study aimed to evaluate the combined in vitro efficacy of terbinafine and ketoconazole against Aspergillus species with terbinafine high MIC values isolated from patients with otomycosis.84 Aspergillus species with high MIC values to terbinafine (≥ 4 µg/ml), consisting of A. flavus, A. tubingensis, A. niger, and A. terreus, were included in this study. The checkerboard microdilution method evaluated the in vitro interactions using the CLSI reference technique. Synergistic effects were observed for 66.67% (56/84) of all isolates (FICI ranging from 0.19 to 0.5). However, the interactions of terbinafine and ketoconazole exhibited indifference in 33.33% (28/84) of the isolates, and no antagonism was observed for any combination. The interaction of terbinafine and ketoconazole showed synergistic activity against Aspergillus species with high MIC values, suggesting that this is an alternative and promising approach for treating otomycosis.

Otomycosis caused by the cryptic and emerging species Aspergillus sydowii: two case reports

Two cases of otomycosis have been reported in patients undergoing tympanomastoidectomy. The first one had chronic otitis media, hypertrophic concha and nasal septum deviation, tympanic perforation and otorrhea. The second had otalgia, pruritus, chronic otitis media and cholesteatoma. Direct examination showed mycelial septate filaments with a branch at an angle close to 45°, later identified as Aspergillus sydowii by sequencing the BenA and CaM genes. Susceptibility testing showed low MIC of amphotericin B, itraconazole, ketoconazole and ciclopirox olamine. In both cases, ketoconazole was instituted for 10 days. Otomycosis is a challenge as it is primarily recurrent in patients undergoing surgery. The clinical implication, the identification of the emerging pathogen and the determination of MIC were necessary for the knowledge of the epidemiological profile and establishment of the treatment.

Environmental Factors Affecting Diversity, Structure, and Temporal Variation of Airborne Fungal Communities in a Research and Teaching Building of Tianjin University, China

Airborne fungi are widely distributed in the environment and may have adverse effects on human health. A 12-month survey on the diversity and concentration of culturable airborne fungi was carried out in a research and teaching building of Tianjin University. Indoor and outdoor environments were analyzed using an HAS-100B air sampler. A total of 667 fungal strains, belonging to 160 species and 73 genera were isolated and identified based on morphological and molecular analysis. The most abundant fungal genera were Alternaria (38.57%), Cladosporium (21.49%), and Aspergillus (5.34%), while the most frequently appearing species was A. alternata (21%), followed by A. tenuissima (12.4%), and C. cladosporioides (9.3%). The concentration of fungi in different environments ranged from 0 to 150 CFU/m3 and was significantly higher outdoor than indoor. Temperature and sampling month were significant factors influencing the whole building fungal community, while relative humidity and wind speed were highly correlated with fungal composition outdoor. Variations in the relative abundance of major airborne fungal taxa at different heights above-ground could lead to different community structures at different floors. Our results may provide valuable information for air quality monitoring and microbial pollution control in university building environments.

Black aspergilli as causes of otomycosis in the era of molecular diagnostics, a mini-review

Otomycosis refers to the fungal infection of the external auditory canal, and less commonly the middle ear. A wide range of fungi can cause this disease, however, the most common etiologies are species of Aspergillus and Candida. Until recent years, Aspergillus niger was thought to be the prevailing species of the genus Aspergillus that causes otomycosis. Using molecular methods, now, it is known that Aspergillus section Nigri comprises several morphologically similar species and all black Aspergillus isolates are not necessarily equivalent to Aspergillus niger. In this review, we focus on the species within the Aspergillus section Nigri and their role as the causative agents of otomycosis.

Identification of molds with MALDI-TOF mass spectrometry: performance of the newly developed MSI-2 application in comparison with the Bruker filamentous fungi database and MSI-1

Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) represents a promising tool for the rapid and efficient identification of molds, but improvements are still necessary to achieve satisfactory results when identifying cryptic species. Here, we aimed to validate a new web application, MSI-2, which replaces MSI-1, an application that was built and deployed online in 2017. For the evaluation, we gathered 633 challenging isolates obtained from daily hospital practice that were first identified with DNA-based methods, and we submitted their corresponding mass spectra to three identification programs (Bruker, MSI-1 and MSI-2). The MSI-2 application had a better identification performance at the species level than MSI-1 and Bruker, reaching 83.25% correct identifications compared with 63.19% (MSI-1), 38.07% (Bruker with 1.7 threshold) and 21.8% (Bruker with 2.0 threshold). The MSI-2 application performed especially well for Aspergillus and Fusarium species, including for many cryptic species, reaching 90% correct identifications for Aspergillus species and 78% for Fusarium species compared to 69% and 43% with MSI-1. Such improvement may have a positive impact on patient management by facilitating the identification of cryptic species potentially associated with a specific antifungal resistance profile.

Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) Analysis for the Identification of Pathogenic Microorganisms: A Review

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been used in the field of clinical microbiology since 2010. Compared with the traditional technique of biochemical identification, MALDI-TOF MS has many advantages, including convenience, speed, accuracy, and low cost. The accuracy and speed of identification using MALDI-TOF MS have been increasing with the development of sample preparation, database enrichment, and algorithm optimization. MALDI-TOF MS has shown promising results in identifying cultured colonies and rapidly detecting samples. MALDI-TOF MS has critical research applications for the rapid detection of highly virulent and drug-resistant pathogens. Here we present a scientific review that evaluates the performance of MALDI-TOF MS in identifying clinical pathogenic microorganisms. MALDI-TOF MS is a promising tool in identifying clinical microorganisms, although some aspects still require improvement.