The Hong Kong Hospital Authority held a two-day conference starting on May 16. Dr. Calvin Chong Yeow Kuan, Consultant Doctor at the Department of Pathology, Princess Margaret Hospital, delivered a presentation on Accurate Fungal Classification by DNA Sequencing. He discussed the application of fungal DNA sequencing in accurately identifying the sources of poisoning.
Chong explained that cases of poisoning caused by wild mushrooms include gastrointestinal discomfort due to consuming the green-spored parasol mushroom (Chlorophyllum molybdites) and liver failure caused by consuming the death cap mushroom (Amanita phalloides).
Additionally, cases of poisoning from purchased mushrooms include gastrointestinal discomfort resulting from consuming mixed varieties of mushrooms called boletes. Over the past three years, the government’s Centre for Food Safety has issued five warnings to the public to refrain from consuming toxic fungi.
Chong said mushroom poisoning analysis relied on clinical symptoms exhibited by patients, identification of mushrooms by mycologists, and biochemical analysis (such as urine and blood tests) for toxin detection, with an accuracy rate of approximately 70-80 percent.
However, diagnosing difficulties arise when patients fail to provide mushroom consumption history, mushrooms are cooked or chopped into unrecognizable forms, or when rare mushroom toxins need more analysis.
In 2018, the Toxicology Reference Laboratory established by the Hospital Authority at Margaret Hospital began experiments using mushroom samples collected from poisoning cases and residual substances in patients’ stomach contents for mushroom DNA sequence analysis. They achieved a breakthrough and extended the application of this technique to the clinical level, making it a permanent service since 2020.
Regarding fungal DNA testing, samples or residual substances are collected, and DNA is extracted. PCR and sequencing techniques are then used to obtain gene sequences. Subsequently, comparative genomics compares the gene sequences with internationally recognized species gene databases to identify similar fungal species.
Chong mentioned that local mycologists (fungi specialists) collaborated in testing 43 fungal specimens from 25 clinical poisoning cases, confirming 86 percent of the collected samples as known species and the remaining 14 percent as a genus.
In this study, all samples were accurately identified, providing additional information in 76-80 percent of the cases compared to traditional methods and reducing unnecessary examinations.
Chong emphasized the advantages of DNA testing for fungi, including providing additional information beyond traditional methods in clinical settings, accurately identifying poisoning sources, and reducing unnecessary examinations. Regarding public health, if toxic mushrooms are identified in the market or growing in Hong Kong, the relevant departments can be informed for follow-up actions.
Furthermore, this technology can also be used to test for plant poisoning, such as rotenone (a natural compound found in certain seeds, roots, and plant stems used as insecticides and herbicides), which is inedible and causes lactic acidosis (lactic acid in the bloodstream).
As for future research directions, Chong mentioned improving plant poisoning tests through genetic testing, addressing the issue of multiple fungal species coexisting in food through next-generation gene sequencing, resolving “mushroom soup poisoning” problems, developing rapid genetic tests for death cap mushroom toxins to expedite the use of antidotes, and utilizing third-generation gene sequencing to enhance laboratory speed.
