Abstract
Given the opportunity and the host immune status, Aspergillus flavus can produce aspergillosis affecting various body organs, while its toxin, Aflatoxin B1 (AFB1) has been implicated as a carcinogen in hepatocellular carcinoma. Based on previous findings, A. flavus can be divided into two groups, (i) isolates that can synthesize AFB1, and (ii) isolates unable to produce AFB1. The aim of this study was to assess whether AFB1 can be used as a marker to differentiate clinical and non-clinical isolates of A. flavus. Representative clinical isolates were obtained from patients while non-clinical isolates were obtained from the environment. Isolates were identified as A. flavus using selective media. AFB1 production was assessed through cultural assays and genes for aflatoxin production, aflR and aflS, were amplified using PCR. Conditioned media and methanol extract of A. flavus isolates were prepared and tested for AFB1 presence using Liquid Chromatography-Mass Spectrometry (LC-MS). Additionally, conditioned media and extract were tested for their cytotoxic effects on primary human brain microvascular endothelial cells (HBMEC) and immortalized human heptaoma cells (Huh7). Both clinical and non-clinical isolates of A.flavus exhibited aflatoxin production, albeit some clinical isolates produced excessive AFB1 (up to 15785 ng/mL). Importantly, A. flavus isolates produced higher levels of AFB1, exhibited increased host cell cytotoxicity, whereas strains exhibiting negligible amount of aflatoxin exhibited minimal cytotoxic effects suggesting AFB1 as a marker for pathogenic potential of A. flavus. The ability of aflatoxigenic A. flavus to produce host cell death in primary cells raises additional concern for patients suffering from A. flavus infection.
Highlights
Aspergillus flavus is a saprotrophic fungus that is widely distributed in the environment
Given the access and the host immune status, A. flavus can be pathogenic for humans and may result in different types of aspergillosis such as allergic bronchopulmonary aspergillosis, invasive aspergillosis or aspergilloma, each affecting the body in different ways [1,2]
Culture assays demonstrated the presence of aflatoxin B1 (AFB1) in both clinical and non-clinical isolates of Aspergillus flavus
Summary
Aspergillus flavus is a saprotrophic fungus that is widely distributed in the environment. A. flavus is the major species responsible for the production of aflatoxins. Approximately 4.5 billion persons living in developing countries are frequently exposed to unchecked amounts of the mycotoxin [5]. Regions such as the sub-Saharan Africa, China, and Southeast Asia are more susceptible to aflatoxin-related hepatocellular carcinoma because of favorable temperatures for fungal growth and poor processing of aflatoxin-contaminated foods. A gene cluster of 30 genes encodes for aflatoxin biosynthesis. The major regulatory gene is aflR, and is located in the center of the cluster and is needed for the transcriptional activation of structural genes thereby acting as a positive regulator of expression of AFB1. The aim of this study was to assess whether AFB1 can be used as a marker to differentiate clinical and non-clinical isolates of A
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