酸適應對腸炎弧菌生理特性及其環境壓力耐受性之影響

Abstract

本研究之目的為探討酸適應或酸挑戰對腸炎弧菌菌株生存能力、細胞形態、細胞洩漏、生長和耐熱性溶血素產生之影響，研究中亦測試未適應和酸適應之腸炎弧菌菌株於酸 (pH 4.5)、乙醇 (8%)、高鹽 (20%)、過氧化氫 (20 ppm) 壓力及模擬胃腸道環境中之存活能力。 實驗中將三株與台灣食品中毒案件相關之腸炎弧菌菌株以 pH 5.5進行90分鐘之酸適應處理。結果顯示，酸適應增加所試三株腸炎弧菌之耐酸性。氯黴素處理可抑制腸炎弧菌耐酸性反應之發生。與未適應之控制組相較，在酸適應之腸炎弧菌菌株上可觀察到其在後續酸挑戰中呈現較輕微之細胞表面傷害。 此外，在暴露於酸適應和酸挑戰後，在菌株間觀察到細胞中260和280 nm吸光物質有不同程度之洩漏。無論是否酸挑戰，酸適應之腸炎弧菌在一些選擇性培養基上之生存菌數較在非選擇性培養基上少。未適應和酸適應之腸炎弧菌在 TSB-3% NaCl 與添有不同碳源及氮源基礎培養基中之生長相似。然而，當在 TSB-3% NaCl 中生長時，酸適應之菌株比未適應之菌株產生較少量之耐熱性溶血素。 另一方面，酸適應增加腸炎弧菌菌株690和 BCRC 13025之乙醇耐受性，但在 BCRC 13023上則無。在酸適應後，三菌株間對高鹽之耐受性具有差異性。然而，酸適應之腸炎弧菌菌株較其未適應之控制組對過氧化氫更敏感。此外，酸適應亦可誘導所試部分菌株對模擬胃腸道環境之交叉保護作用。

The objective of this study was to investigate the effects of acid adaptation or acid challenge on the survivability, cell morphology, cell leakage, growth and thermostable direct hemolysin (TDH) production of Vibrio parahaemolyticus strains. The survivals of non-adapted and acid-adapted V. parahaemolyticus strains in acid (pH 4.5), ethanol (8%), high salt (20%), hydrogen peroxide (20 ppm) stresses and simulated gastrointestinal conditions were also examined. In the experiments, three strains of V. parahaemolyticus (690, BCRC 13023 and BCRC 13025), involved in food poisoning outbreaks in Taiwan, were subjected to acid adaptation at pH 5.5 for 90 min. Results showed that acid adaptation increased the acid tolerance of the three test strains of V. parahaemolyticus. Chloramphenicol treatment could inhibit the adaptive acid tolerance response (ATR) occurred in V. parahaemolyticus. Acid-adapted strains of V. parahaemolyticus showed a relatively minor cell surface damage in subsequent acid challenge compared with their non-adapted controls. Additionally, different levels of cell leakage of 260 and 280 nm absorbing materials were observed among strains after exposure to acid adaptation and challenge. Regardless of acid challenge, the viable populations of acid-adapted V. parahaemolyticus were less on some selective media than on non-selective media. The growth of non-adapted and acid-adapted V. parahaemolyticus was similar in TSB-3% NaCl and basal media supplemented with various carbon and nitrogen sources. Nevertheless, acid-adapted strains produced less amounts of TDH than non-adapted strains when they were grown in TSB-3% NaCl. On the other hand, acid adaptation increased the ethanol tolerance in V. parahaemolyticus strains 690 and BCRC 13025, but not in BCRC 13023. Differences in the tolerance to high salts were noted among the three strains after acid adaptation. However, acid-adapted strains of V. parahaemolyticus were more susceptible to hydrogen peroxide than their non-adapted controls. Furthermore, acid adaptation also induced cross-protection against simulated gastrointestinal conditions in the part of the test strains.