Clinical Presentations, Cluster Analysis and Laboratory-Based Investigation of Aspergillus Otomycosis—A Single Center Experience

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.

Study on the microbial diversity of ear canal secretions from patients with otomycosis

Otomycosis is caused by fungi, which usually cause discharge and additional discomfort. The highest incidence of otomycosis occurs in summer. To better treat this disease, it is necessary to study the microbial diversity of otomycosis secretions. In this regard, this study used high-throughput sequencing technology to determine the microbial diversity of the ear canal secretions of six typical patients with otomycosis in Wuhan via internal transcribed spacer (ITS) and 16S rRNA analyses and proposed a reasonable clinical treatment plan. Six patients with otomycosis in the Department of Otorhinolaryngology, Hubei Third People's Hospital Affiliated with Jianghan University, were selected from June 2022 to August 2022. The results showed that Staphylococcus spp. (average abundance 29.05%) was the dominant bacteria and Aspergillus spp. (average abundance 90.68%) was the dominant fungus involved in otomycosis secretion. Aspergillus spp. can cause inflammation of the external auditory canal combined with bacterial infections such as Staphylococcus spp., which can cause discharge in the ear canal. High-throughput sequencing provides comprehensive information on the microbial community involved in otomycosis discharge and will aid in evaluating the efficacy of clinical treatment and medication.

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.

Etiology, Predisposing Factors, Clinical Features and Diagnostic Procedure of Otomycosis: A Literature Review

Otomycosis (OM) is a superficial fungal infection of the external auditory canal (EAC) with a worldwide prevalence ranging from 9% to 30%. Commonly, otomycoses are caused by Aspergillus (A.) niger complex and Candida spp. Other causative agents are yeasts of the genera Cryptococcus spp., Rhodotorula spp., Geotrichum candidum, dermatophytes (Trichophyton mentagrophytes), and non-dermatophytes molds (Fusarium spp., Penicillium spp., Mucorales fungi). The widest range of different species causing OM are found in the territories of Iran, India, China, Egypt, Mexico, and Brazil. Fungal infection of the EAC varies from mild to severe forms. It can be acute, subacute, or chronic, and is often unilateral, while the bilateral form is more common in immunocompromised patients. From an epidemiological point of view, tropical and subtropical climates are the most significant risk factor for the development of otomycosis. Other predisposing conditions include clothing habits, EAC hygiene practices, long-term antibiotic therapy, diabetes, and immunodeficiency. Since it is often difficult to distinguish otomycosis from an infection of a different origin, laboratory-based evidence, including standard procedures (microscopy and cultivation), is essential for diagnosis. For the treatment of this superficial fungal infection, there are no official therapeutic guidelines and protocols. However, many antifungals for local application, such as polyene, imidazoles, and allylamines, can be applied, as well as systemic antimycotics (triazoles) in severe forms of infection.

Relapsing Aspergillus otomycosis despite prolonged systemic antifungal therapy and resolution after topical voriconazole administration: A case report

We report a case of intractable Aspergillus otomycosis with multiple relapses despite conventional topical and systemic antifungal treatment, and adjunctive usage of hyperbaric oxygen therapy. Of note, otomycosis relapsed even after six months of continuous systemic antifungal treatment with therapeutic drug levels and without treatment interruption; and only resolved after application of topical voriconazole. (max. 75 words).

Poly-(lactic-co-glycolic) Acid Nanoparticles Entrapping Pterostilbene for Targeting Aspergillus Section Nigri

Poly-(lactic-co-glycolic) acid (PLGA) is a biodegradable, biosafe, and biocompatible copolymer. The Aspergillus section Nigri causes otomycosis localized in the external auditory canal. In this research, Aspergillus brasiliensis, a species belonging to the Nigri section, was tested. Coumarin 6 and pterostilbene loaded in poly-(lactic-co-glycolic) acid nanoparticles (PLGA-coumarin6-NPs and PLGA-PTB-NPs) were tested for fungal cell uptake and antifungal ability against A. brasiliensis biofilm, respectively. Moreover, the activity of PLGA-PTB-NPs in inhibiting the A. brasiliensis infection was tested using Galleria mellonella larvae. The results showed a fluorescence signal, after 50 nm PLGA-coumarin6-NPs treatment, inside A. brasiliensis hyphae and along the entire thickness of the biofilm matrix, which was indicative of an efficient NP uptake. Regarding antifungal activity, a reduction in A. brasiliensis biofilm formation and mature biofilm with PLGA-PTB-NPs has been demonstrated. Moreover, in vivo experiments showed a significant reduction in mortality of infected larvae after injection of PLGA-PTB-NPs compared to free PTB at the same concentration. In conclusion, the PLGA-NPs system can increase the bioavailability of PTB in Aspergillus section Nigri biofilm by overcoming the biofilm matrix barrier and delivering PTB to fungal cells.