In vitro activity of terbinafine and itraconazole against Aspergillus species isolated from otomycosis

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.

Otomycosis: The foremost aetiological agent causing otitis externa and the antifungal susceptibility pattern in North-Western Iran

BACKGROUND

Otomycosis is considered a recurring fungal ear infection. The external auditory canal provides an appropriate and optimal situation for fungal growth.

OBJECTIVES

The study aimed to identify the causative agents of otomycosis and determine corresponding antifungal drug susceptibility patterns in north-western Iran.

METHODS

From October 2020 until November 2021, 200 patients attended an otolaryngology referral centre with otitis externa, and their ear discharge and debris were examined and cultured. The identification of the fungal agents was implemented by polymerase chain reaction-restriction fragment length polymorphism and sequencing. In vitro antifungal susceptibility testing of the isolates was conducted in accordance with the CLSI broth microdilution protocols.

RESULTS

The prevalence of otomycosis was measured 50.5% (n = 101/200). The majority of patients were in their forties (n = 35, 34.6%) and female (n = 57, 56.4%), and the most prevalent symptom was otalgia (56.4%). The most underlying factor was remarked manipulation employing a cotton swab (65.3%). Regarding fungus, Aspergillus section Nigri (58.57%) was the foremost isolate, followed by Aspergillus section Flavi (19.23%) and Candida parapsilosis (14.96%). The predominance of Aspergillus isolates had minimal in vitro sensitivity to tioconazole and nystatin. Candida species represented higher geometric mean minimum inhibitory concentrations (MIC) against nystatin. The MIC of three Aspergillus species isolates shown above the epidemiologic cut-off values (ECV) against itraconazole.

CONCLUSIONS

Otomycosis incidence surpassed in comparison with the previous study as the most common cause of otitis externa. The MIC distribution of Aspergillus species isolates against triazole antifungals is close to the defined ECVs and likely outrun it over time.

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.

Molecular Identification and Antifungal Susceptibility of Yeasts and Molds Isolated from Patients with Otomycosis

Fungal otitis externa, an infection of the external auditory canal caused by molds and yeasts, accounts for approximately 10-20% of ear canal infections accompanying high recurrence. The purpose of the current study was to assess the pattern of etiological agents of otomycosis and resistance profile as well as the rate of tympanic membrane perforation. A total of 1040 patients with symptoms of fungal otitis externa, in a period of two years, were investigated. The mycological tests revealed the presence of different fungi in 237 ears (22.8%). Fungal otitis was more related to filamentous fungi of the species Aspergillus flavus (54.43%), A. tubingensis (10.97%), and A. niger (8.86%), followed by yeasts, Candida orthopsilosis (7.59%), C. albicans (6.75%), and C. parapsilosis (5.06%). Tympanic membrane perforation rate was found to be 6.75% and was more common with otomycosis caused by A. flavus, A. tubingensis and C. albicans. In antifungal susceptibility tests, all tested drugs showed generally good activity against most isolates of molds and yeasts, while tolnaftate, clotrimazole, nystatin, and terbinafine had lowest effects. We found that among Aspergillus isolates, one A. niger isolate was resistant to voriconazole, and one A. flavus isolate was resistant to amphotericin B. Furthermore, among Candida species, three isolates of C. orthopsilosis showed high MIC values to fluconazole, two C. albicans isolates were considered fluconazole resistant and one isolate of C. parapsilosis was resistant to caspofungin and 3 isolates were resistant to fluconazole. Regarding the existence of the cases with perforated tympanic membrane and emerging species causing fungal otitis in the current report, the importance of the early physical examination, precise molecular identification, and the antifungal susceptibility evaluation is highlighted.

Antifungal susceptibility profiles of otomycosis etiological agents in Ahvaz, Iran

Background and Purpose

Otomycosis is a secondary ear fungal infection among predisposed individuals in humid conditions. Aspergillus species are the most common etiologic agents of this infection. Several ototopical antifungals are currently used for the treatment of this disease; however, recurrence and treatment failure are usually observed in some cases. Regarding this, the present study was conducted to investigate the antifungal activity of caspofungin, azoles, and terbinafine against the isolated agents of otomycosis.

Materials and Methods

This study was conducted on the specimens collected from 90 patients with otomycosis. The samples were cultured on Sabouraud dextrose agar and identified based on morphological characteristics, physiological tests, and microscopic features. Furthermore, the microdilution method was used for antifungal susceptibility testing according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Finally, the minimum inhibitory concentration (MIC) and minimum effective concentration (MEC) ranges, MIC/MEC₅₀, MIC/MEC₉₀, and geometric mean (GM) MIC/MEC were calculated for the isolates.

Results

According to the results, 77 patients with otomycosis were positive for different Aspergillus (88.3%) and Candida (11.7%) species. Aspergillus niger complex (n=36) was found to be the most common agent, followed by A. flavus, A. terreus, and A. nidulans complexes. Furthermore, epidemiological cutoff values (ECVs) were lower than those presented by the CLSI for itraconazole and caspofungin in 98.5% and 42.6% of Aspergillus species, respectively. Terbinafine exhibited a great activity against Aspergillus species, while fluconazole revealed a low activity against both Aspergillus species. Based on the results, 77.8% of Candida species were resistant to caspofungin; however, miconazole and econazole had low MIC ranges.

Conclusion

Aspergillus niger and A. flavus complexes were identified as the most common agents accounting for 85.7% of the isolates. In addition, terbinafine was identified as the best antifungal for both Aspergillus and Candida species. Moreover, tested azoles had relatively low MICs, whereas most of the isolates had the MIC values beyond the caspofungin ECVs.

Eradicating Otomycosis with Terbinafine Solution: Basic and Clinical Investigation

BACKGROUND

Otomycosis still remains intractable in clinical practice, likely because topical antifungal agents lack efficacy or are potentially toxic to the inner ear end organs.

OBJECTIVES

The aim of this study was to investigate whether terbinafine solution is a potential candidate for treating intractable otomycosis in humans. In addition, the toxic effect on the inner ear was also assessed by animal models treated with terbinafine.

METHODS

Guinea pigs were instilled with 0.1 mL terbinafine (10 and 25 mg/mL) in the left round window membrane. At 2 weeks after treatment, all animals underwent an inner ear test battery and were then sacrificed for morphological study. Clinically, 20 patients with otomycosis were treated with terbinafine solution at a dosage of 0.4 mg.

RESULTS

All terbinafine-treated animals showed intact inner ear function when total dosage of terbinafine was <2.5 mg, which was further confirmed by morphological study. Subsidence of otomycosis was achieved in all 20 patients 1 week after treatment with terbinafine (0.4 mg) without untoward effect. No evidence of recurrence was noted 1 year after treatment.

CONCLUSION

The paucity of inner ear toxicity of terbinafine even at a dosage of 2.5 mg was identified in guinea pig models morphologically and physiologically. Topical application of terbinafine solution at a dosage of 0.4 mg may be a potential treatment for otomycosis in humans.

Successful treatment of a recurrent Aspergillus niger otomycosis with local application of voriconazole

Fungal otitis (otomycosis) is a common infection encountered by otolaryngologists. Nevertheless, its management can be challenging because of its high recurrence rate and of the limited therapeutic options. A 45-year-old woman suffered from recurrent otomycosis. The ineffectiveness of successive antibiotic cures and repeated topical treatments with nystatin and then with econazole cream led to perform microbiological analyses. Culture of ear swab grew Aspergillus niger. The use of a 1% voriconazole sterile solution previously validated for treatment of eye infections was considered after ensuring the absence of known ototoxic effects of the antifungal and of the excipients. The patient was advised to apply locally this voriconazole solution daily for 14 days (3 drops, 3-4 times a day). Full recovery was obtained at the end of the treatment, and no relevant side effects were noticed. More than one year after completion of therapy, there was no recurrence. Our observation shows that voriconazole 1% solution is an interesting option for treating otomycosis which failed to respond to usual therapeutic options. Further prospective studies are now warranted to confirm these findings.

[Otomycosis: the modern view of etiology and management]

This article deals with the modern approaches to the diagnostics and treatment of fungal ear infection depending on the localization of the inflammatory process and the species of the causative fungal agent with special reference to the factors underlying the development of otomycosis under the present-day conditions based on the results of the analysis of the studies carried out during the period from 2010 to 2014. The materials of the examination of 2152 patients who applied for the medical care to various clinical departments of the Institute and were found to present with chronic inflammatory ear pathology were available for the analysis. Fungal lesions were diagnosed in 495 (23%) patients with this condition. Fungal lesions of the external ear were the predominant form of pathology; they were documented in 331 (67%) patients. Fungal otitis media was diagnosed in 85 (17%) patients and fungal lesions of the postoperative cavity in 79 (16%) patients suffering from otomycosis. 65% of the patients presenting with external fungal otitis, 20% of those with fungal otitis media, and 95% of the patients with inflammation of the postoperative cavity were infected with mold fungi dominated by the genus Aspergillus spp. 79 (16%) patients suffering from otomycosis. In 35% of the patients presenting with fungal external otitis, 80% of those with fungal otitis media, and 5% of the patients with inflammation of the postoperative cavity of the middle ear, the causative agents of the disease were the fungi Candida spp. The authors describe the modern schemes for the treatment of otomycosis elaborated at the L.I. Sverzhevskiy Research Institute of Clinical Otorhinolaryngology.

Type of Antifungals: Does it Matter in Empirical Treatment of Otomycosis?

To evaluate the efficacy of clotrimazole, miconazole and fluconazole in empirical treatment of otomycosis in our tertiary care hospital and to appraise possible better outcome in otomycosis. Two hundred and ninety five patients who presented with clinical otomycosis at our Melmaruvathur Adiparasakthi Institute of medical sciences were incorporated in this study. Two hundred and fourteen patients who satisfied our criteria were recognized and they were randomly alienated into three groups A, B, C. Group A patients were advised to instill clotrimazole ear drops by themselves. Miconazole cream instillation were done by our trained personal in group B patients. Group C patients were advised to use fluconazole ear drops. Patients were educated to keep ear dry and instructed to come for evaluation in first and second week after initial visit. A randomized double blinded prospective study. In the first week, clotrimazole had a good response than miconazole and fluconazole in our patients and in the second week, our patients showed a drastic response in patients instilling flucanozole ear drops compared to those using micanozole and clotrimazole. This better outcome doesn't show statistical significance since p value is 0.882. Clotrimazole drops, miconazole cream and Fluconazole drops showed almost same therapeutic efficacy in Otomycosis.

Lamisil, a potent alternative antifungal drug for otomycosis

Background and Purpose:

Otomycosis is an acute, subacute or chronic fungal infection of the pinna, the external auditory meatus and the ear canal caused mainly by several species of saprophytic fungi. Lamisil (Terbinafine) is an allylamine antifungal agent, that is used both in the topical and oral administration for the treatment of dermatophytosis, cutaneous candidiasis, and the pityriasis versicolor. We investigated the in vitro activity of clotrimazole, miconazole, nystatin, and Lamisil against the agents of otomycosis.

Materials and Methods:

Fifteen clinically obtained isolates from otomycosis (Aspergillus species; n=13, and Candida species, n=2) and 8 environmental isolates of Aspergillus were tested. The disk diffusion method was employed to detect susceptibility. In the present study, the in vitro activity of the terbinafine with clotrimazole, miconazole, and nystatin against several isolates of Aspergillus and Candida with different sources were compared.

Results:

Out of 23 isolates of Aspergillus, Candida 4(17.4%) and 1(4.4%) were resistant to nystatin and miconazole, respectively. In addition, all tested organisms were sensitive to clotrimazole and terbinafine. Statistical analysis has shown that there are no significant differences on the effects of clotrimazole, miconazole and, terbinafine on saprophytic (environmental) and pathogenic isolates of A. niger, A. flavus, and A. terreus (P value= 0.85). In addition, all tested organisms were found to be highly susceptible to terbinafine (P< 0.04).

Conclusion:

This is a new approach for the possible use of Lamisil for the treatment of otomycosis.

The ototoxic effect of intratympanic terbinafine applied in the middle ear of rats

Background

Otomycosis is defined as an infection of the external ear canal with fungal agents. The treatment of the disease is cleansing and drying of the external ear canal, identification and treatment of any predisposing factors and application of topical antifungal agents. Terbinafine is used as an antifungal agent to treat otomycosis. We proposed to investigate the probable ototoxic effect of terbinafine solution on auditory brain stem response (ABR) and distortion product otoacoustic emission (DPOAE) when applied intratympanically in the middle ear of rats.

Methods

The experiment was performed on 30 female Wistar albino rats. Thirty animals were divided into three groups of 10 animals each. 1% terbinafine solution was administered to the first group (group T). The second group (group G) was administered 40 mg/ml gentamicin solution (ototoxic control). The third group (group S) was administered saline solution (negative control). Baseline DPOAE measurements and ABR testing from the left ears were obtained from the animals in all groups under general anesthesia. Ear solutions were applied in the middle ear intratympanically with a dental needle. Treatment was initiated after baseline measurements and repeated once every two days for fifteen days.

Results

Pre and post-treatment DPOAE responses for all tested frequencies of group T and Group S showed no statistically significant difference. However, the group G demonstrated a significant change in ABR thresholds and DPOAE responses.

Conclusions

Terbinafine solution is a broad spectrum antifungal agent effective in the treatment of otomycosis. The present study demonstrated that its direct administration in the middle ear of rats does not affect inner ear function as measured by ABR and DPOAE responses.

In vitro interactions of amantadine hydrochloride, R-(-)-deprenyl hydrochloride and valproic acid sodium salt with antifungal agents against filamentous fungal species causing central nervous system infection

The mortality rates of fungal infections that affect the central nervous system are high in consequence of the absence of effective antifungal drugs with good penetration across the blood-brain barrier and the blood-cerebrospinal fluid barrier. In the present work in vitro antifungal activities of three good penetrating non-antifungal drugs (amantadine hydrochloride, R-(-)-deprenyl hydrochloride, valproic acid sodium salt) and their combinations with three antifungal agents (amphotericin B, itraconazole, terbinafine) were tested with broth microdilution method against eight fungal isolates belonging to Zygomycetes (Lichtheimia corymbifera, Rhizomucor miehei, Rhizopus microsporus var. rhizopodiformis, Saksenaeavasiformis) and Aspergillus genus (A. flavus, A. fumigatus, A. nidulans, A. terreus). These are known to be possible agents of central nervous fungal infections (CNFI). When used alone, the investigated nonantifungal drugs exerted slight antifungal effects. In their combinations with antifungal agents they acted antagonistically, additively and synergistically against zygomyceteous isolates. Primarily antagonistic interactions were revealed between the investigated drugs in case of Aspergilli, but additive and synergistic interactions were also observed. The additive and synergistic combinations allowed the usage of reduced concentrations of antifungal agents to inhibit the fungal growth in our study. These combinations would be a basis of an effective, less toxic therapy for treatment of CNFI.

Enhanced topical delivery of terbinafine hydrochloride with chitosan hydrogels

Chitosan-based carriers have important potential applications for the administration of drugs. In the present study, topical gel formulations of terbinafine hydrochloride (T-HCl) were prepared using different types of chitosan at different molecular weight, and the antifungal inhibitory activity was evaluated to suggest an effective formulation for the treatment of fungal infections. The characteristics of gel formulations were determined with viscosity measurements and texture profile analysis. Stability studies were performed at different temperatures during 3 months. The ex vivo permeation properties were studied through rat skin by using Franz diffusion cells. The antifungal inhibitory activity of formulations on Candida species and filamentous fungi was also examined with agar-cup method. The microbiological assay was found suitable for determination of in vitro antifungal activity of T-HCl. A marketed product was used to compare the results. The antifungal activity of T-HCl significantly increased when it was introduced into the chitosan gels. A higher drug release and the highest zone of inhibition were obtained from gels prepared with the lowest molecular weight chitosan (Protasan UP CL 213) compared to that of other chitosan gels and marketed product. These results indicated the advantages of the suggested formulations for topical antifungal therapy against Candida species and filamentous fungi.

Ototopical antifungals and otomycosis: a review

There has been an increase in the prevalence of otomycosis in recent years. This has been linked to the extensive use of antibiotic eardrops. Treatment of otomycosis is challenging, and requires a close follow-up. We present a review of the literature on otomycosis, the topical antifungals most commonly used, and discuss their ototoxic potential. Candida albicans and Aspergillus are the most commonly identified organisms. Antifungals from the Azole class seem to be the most effective, followed by Nystatin and Tolnaftate.

Use of terbinafine in rare and refractory mycoses

Terbinafine is the only systemic allylamine antifungal currently available. Its mechanism of action is unique and sets it apart from other agents. Although it is primarily used for dermatophyte infections, such as onychomycosis and tinea pedis, terbinafine has broad in vitro activity against a variety of non-dermatophyte fungal pathogens, including Candida spp. and many molds. In addition, synergistic activity is noted with other antifungals, notably triazoles. Multiple case reports exist of its use for unusual and refractory fungal infections, but no systematic review is available. We review the current literature with regard to in vitro data and clinical experience with terbinafine in the treatment of rare and refractory mycoses.