Many elements of the normal flora may act as opportunistic pathogens. 很多正常菌群都可能是条件致病。
Septicum is part of the normal gastrointestinal tract flora but when infection occurs, it is often fatal, especially in the diabetic population. 坏疽毒素是胃肠道的正常菌群，但一旦发生感染却是致命的，特别是糖尿病患者。
