Genetic Diversity and In Vitro Antifungal Susceptibility of 200 Clinical and Environmental Aspergillus flavus Isolates

Abstract

Aspergillus flavus has been frequently reported as the leading cause of invasive aspergillosis in certain tropical and subtropical countries. Two hundred A. flavus strains originating from clinical and environmental sources and collected between 2008 and 2015 were phylogenetically identified at the species level by analyzing partial ␤-tubulin and calmodulin genes. In vitro antifungal susceptibility testing was performed against antifungals using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) broth microdilution method. In addition, genotyping was performed using a short-tandem-repeat (STR) assay of a panel of six microsatellite markers (A. flavus 2A, 2B, 2C, 3A, 3B, and 3C), in order to determine the genetic variation and the potential relationship between clinical and environmental isolates. The geometric means of the minimum inhibitory concentrations/minimum effective concentrations (MICs/MECs) of the antifungals across all isolates were (in increasing order): posaconazole, 0.13 mg/liter; anidulafungin, 0.16 mg/liter; itraconazole, 0.29 mg/liter; caspofungin, 0.42 mg/liter; voriconazole, 0.64 mg/liter; isavuconazole, 1.10 mg/liter; amphotericin B, 3.35 mg/liter; and flucytosine, 62.97 mg/liter. All of the clinical isolates were genetically different. However, an identical microsatellite genotype was found between a clinical isolate and two environmental strains. In conclusion, posaconazole and anidulafungin showed the greatest in vitro activity among systemic azoles and echinocandins, respectively. However, the majority of the A. flavus isolates showed reduced susceptibility to amphotericin B. Antifungal susceptibility of A. flavus was not linked with the clinical or environmental source of isolation. Microsatellite genotyping may suggest an association between clinical and environmental strains, although this requires further investigation.

Azole resistance in Aspergillus species in Southern Taiwan: An epidemiological surveillance study

“…In the present study, all tested azoles showed potent in vitro activity against all A flavus and A oryzae clinical and environmental isolates. This result is consistent with a previous report in which clinical and environmental A flavus isolates were both tested . Unlike A fumigatus , the development of resistance via environmental selection is not currently a concern for A flavus .…”

“…This result is consistent with a previous report in which clinical and environmental A flavus isolates were both tested. 31 Unlike A fumigatus, the development of resistance via environmental selection is not currently a concern for A flavus. Recently, a surveillance study in Korea used CLSI ECVs to reveal that 14% (7/50) of A flavus clinical isolates belonged to a non-wild-type genus.…”

Discrimination of Aspergillus flavus from Aspergillus oryzae by matrix‐assisted laser desorption/ionisation time‐of‐flight (MALDI‐TOF) mass spectrometry

“…In tropical and subtropical countries of the Middle-East, such as Iran, species of Aspergillus section Flavi are reportedly the main aetiological agents of invasive and non-invasive infections. 3,4 The taxonomy of this section is complex and is currently under development. 5 A large number of species in section Flavi are commonly observed plant pathogens producing several mycotoxins.…”

First case of Aspergillus caelatus airway colonization in a Chronic Obstructive Pulmonary Disease patient

“…Although in our case the presence of A. caelatus cannot be related to an active infectious process, it is of importance to consider the in vitro antifungal susceptibility pattern of Aspergillus from the section Flavi and their predominant role as pathogens in tropical and subtropical countries (Taghizadeh-Armaki et al, 2017;Hagiwara et al, 2016). Therefore, it is necessary to know the human pathogenic role of each of them and to develop rapid and easy identification techniques and susceptibility tests.…”