Normal microbial flora的用法和樣例：
例句
- Many elements of the normal flora may act as opportunistic pathogens.
很多正常菌群都可能是條件致病。 - Septicum is part of the normal gastrointestinal tract flora but when infection occurs, it is often fatal, especially in the diabetic population.
壞疽毒素是胃腸道的正常菌群，但一旦發(fā)生感染卻是致命的，特別是糖尿病患者。
