Screening Candida auris through a multiplex stepwise PCR algorithm directly from clinical samples of patients suspected of otomycosis in south of Iran; Detection of five cases.

Background: Otomycosis is an infection of the external auditory canal caused by molds and yeasts with descending frequency. Laboratory diagnosis is usually confirmed by microscopy and culture. However, they are not specific enough to reliably differentiate the causative agents, especially for rare pathogens such as Candida auris. The purpose of the current study was to the molecular screening of C. auris species from direct clinical samples of patients with suspected otomycosis in Southern of Iran.

Materials And Methods: A total of 221 ear aspirates collected from 221 patients with suspected otomycosis over a four-year period. All the ear aspirations were examined with pan-fungal primers, then those with a positive result was included in two separate reaction mixtures simultaneously to identify the most clinically relevant Aspergillus and Candida species. The validity of positive samples for C. auris was assessed by sequencing.

Results: Of the 189 pan-fungal positive PCRs, 78 and 39 specimens contained Aspergillus spp. and Candida spp., respectively. Furthermore, 65 specimens showed simultaneous positive bands in both Candida and Aspergillus species-specific multiplex PCR including five samples/patients with positive result for C. auris (5/189; 2.6%). Four out of five cases with C. auris species-specific PCR were reconfirmed by sequencing, while none were positive for C. auris in culture.

Conclusion: Unfortunately, due to high treatment failure rates of antifungal classes against C. auris species, rapid and accurate identification of patients colonised with C. auris is critical to overcome the challenge of preventing transmission. This PCR assay can be successfully applied for rapid and accurate detection of C. auris directly in patient samples and is able to differentiate C. auris from closely related Candida species.