Characterization of Aspergillus tamarii Strains From Human Keratomycoses: Molecular Identification, Antifungal Susceptibility Patterns and Cyclopiazonic Acid Producing Abilities

Abstract

Aspergillus tamarii appears to be an emerging aetiological agent of human keratomycoses in South India. The investigated strains were isolated from six suspected fungal keratitis patients attending a tertiary care eye hospital in Coimbatore (Tamil Nadu, India), and were initially identified by the microscopic examinations of the scrapings and the cultures. Our data suggest that A. tamarii could be easily overlooked when identification is carried out based on morphological characteristics alone, while the sequence analysis of the calmodulin gene can be used successfully to recognize this species accurately. According to the collected clinical data, ocular trauma is a common risk factor for the infection that gradually developed from mild to severe ulcers and could be healed with an appropriate combined antifungal therapy. Antifungal susceptibility testing revealed that A. tamarii strains are susceptible to the most commonly used topical or systemic antifungal agents (i.e., econazole, itraconazole and ketoconazole) except for natamycin. Moreover, natamycin proved to be similarly less effective than the azoles against A. tamarii in our drug interaction tests, as the predominance of indifferent interactions was revealed between natamycin and econazole and between natamycin and itraconazole as well. Four and five isolates of A. tamarii were confirmed to produce cyclopiazonic acid (CPA) in RPMI-1640 – which is designed to mimic the composition of human extracellular fluids – and in yeast extract sucrose (YES) medium, respectively, which is a widely used culture medium for testing mycotoxin production. Although a ten times lower mycelial biomass was recorded in RPMI-1640 than in YES medium, the toxin contents of the samples were of the same order of magnitude in both types of media. There might be a relationship between the outcome of infections and the toxigenic properties of the infecting fungal strains. However, this remains to be investigated in the future.

Aspergillus tamarii mediated green synthesis of magnetic chitosan beads for sustainable remediation of wastewater contaminants

“…(Fig. 1 A,B), based on the identification key 23 . The morphological identity was further ascertained based on its sequence of ITS fragments.…”

Substantive Morphological Descriptions, Phylogenetic Analysis and Single Nucleotide Polymorphisms of Aspergillus Species From Foeniculum vulgare

“…AFs are severely toxic, mutagenic, carcinogenic, teratogenic, immunosuppressants and are classified as Group1 carcinogens in human beings (Ostry et al, 2017) and hence are of special concern to human, animal and poultry health. A. tamarii is an epidemiological agent of human mycotic keratitis in India (Homa et al, 2019). Although it does not produce aflatoxins, it can induce elaboration of other toxic compounds like cyclopiazonic acid (Dorner et al, 1983;Ito, 1998), hence, posing a threat to human health.…”

Cryptic aspergillosis: a rare entity and a diagnostic challenge

“…Published literature suggests that the occurrence of cryptic species is of importance in stem cell/solid organ transplant patients and its clinical spectrum includes invasive aspergillosis, pneumonia, exacerbation of chronic obstructive pulmonary disease (COPD), keratitis, eyelid infection, onychomycosis, cutaneous infections, wound infection, invasive nasal aspergillosis and nasal polyposis [13,14]. Unfortunately, there are no clinical data for guiding the management of aspergillosis caused by cryptic species.…”