探討長期暴露玉米赤黴烯酮對金黃色葡萄球菌生物膜形成、致病力、抗藥性之影響與其調控機制

Abstract

全球約60-80%的穀物和飼料受到黴菌毒素污染，對人類健康造成重大風險，並導致可觀的經濟損失。玉米赤黴烯酮 (Zearalenone, ZEN) 是一種由鐮刀菌屬黴菌產生的黴菌毒素，廣泛存在於農業環境以及穀類製品與飼料中。同時，金黃色葡萄球菌 (Staphylococcus aureus, S. aureus) 為一種常見的食源性病原菌，能引起食物中毒與多種臨床感染。研究指出，長期暴露環境壓力可促使細菌產生演化適應，而S. aureus亦可能長期暴露於農業或食品環境中污染物如ZEN，進而誘導其壓力反應並促進適應，對全球食品安全與公共衛生造成潛在風險，然而，長期暴露ZEN對S. aureus生理與毒力調控之影響仍尚未明瞭。本研究旨在評估長期重複暴露ZEN對S. aureus生物膜形成、抗生素抗性之影響，以及以秀麗隱桿線蟲 (Caenorhabditis elegans, C. elegans) 為模式生物，評估其感染宿主致病力之影響，並進一步探討其分子調控機制。實驗結果顯示，24小時暴露下，ZEN 10-150 µM顯著促進S. aureus生長，而160-250 µM則抑制其生長，呈現非單一劑量反應。而將S. aureus連續重複暴露於ZEN (0.1、10與50 µM) 45天的長期暴露馴化下，ZEN 0.1與10 µM對菌體生長無明顯影響，但50 µM則逐漸抑制其生長。進一步針對ZEN 10 μM馴化30天之S. aureus進行分析，發現長期暴露於ZEN顯著提升生物膜形成能力 (0.1、10與50 µM ZEN)、對tetracycline與gentamicin之抗藥性 (10 µM ZEN)、以及對C. elegans之感染致死率 (0.1與10 µM ZEN)；並顯著提升相關調控基因之表達，包括壓力反應因子sigB、雙分子調控系統saeR、生物膜相關基因icaACBD、抗藥性相關基因tet(38)，以及致病相關基因sak、coa、lukD與hly。上述顯示長期暴露ZEN會誘導S. aureus提升其環境適應力與致病力。本研究結果有助於釐清黴菌毒素誘發之病原體壓力適應機制，對於食品安全、環境與公共衛生具有重要參考價值。

Approximately 60-80% of global grains and feed are contaminated with mycotoxins, posing significant risks to human health and causing substantial economic losses. Zearalenone (ZEN), a mycotoxin produced by Fusarium fungi, is widely detected in agricultural environments as well as in cereal-based foods and feeds. Meanwhile, Staphylococcus aureus (S. aureus), a common foodborne pathogen, is capable of causing food poisoning and a wide range of clinical infections. Studies have indicated that prolonged exposure to environmental stress can drive adaptive evolution in bacteria. S. aureus may also be long-term exposed to environmental contaminants such as ZEN in agricultural or food-related settings, potentially triggering bacterial stress responses and facilitating evolutionary adaptations, thereby posing a potential threat to global food safety and public health. However, the effects of long-term ZEN exposure on microbial physiology and virulence regulation of S. aureus remain poorly understood. This study aimed to evaluate the effects of prolonged ZEN exposure on S. aureus biofilm formation and antibiotic resistance, and to further evaluate its pathogenicity using Caenorhabditis elegans (C. elegans) as an infection model. Additionally, the study sought to clarify the underlying molecular regulatory mechanisms. The results showed that, under 24-hour treatment, ZEN 10-150 µM significantly promoted S. aureus growth, whereas 160-250 µM inhibited it, revealing a non-monotonic dose-response. Under 45-day repeated exposure to ZEN (0.1, 10, and 50 µM), ZEN 0.1 and 10 µM had no significant effect on bacterial growth, while 50 µM gradually suppressed growth. Further analysis of S. aureus following repeated exposure to 10 µM ZEN for 30 days demonstrated that long-term exposure to ZEN significantly enhanced biofilm formation (0.1, 10 and 50 µM ZEN), resistance to tetracycline and gentamicin (10 µM ZEN), and the lethality rate in infected C. elegans (0.1 and 10 µM ZEN). It also significantly upregulated key regulatory genes, including the stress response regulator sigB, the two-component system regulator saeR, biofilm-associated genes icaACBD, antibiotic resistance-related genes tet(38), and virulence-related genes sak, coa, lukD, and hly. These findings suggest that long-term exposure to ZEN can induce adaptive responses in S. aureus, enhancing its environmental fitness and pathogenic potential. This study provides valuable insights into the mechanisms of mycotoxin-induced stress responses in pathogens, with implications for food safety, as well as environmental and public health.