一、前言人类生存的环境中有无数的微生物,而所以不常生病是决定于有机体的天然及获得性抵抗微生物的能力,以及与微生物致病力间的平衡性。当这个平衡被破坏后,有一些在一般情况下不致病的微生物,有可能侵入机体而致病。这就是所谓的条件致病菌。 I. INTRODUCTION There are innumerable microorganisms in the environment of human existence. Therefore, the uncommon illness depends on the organism’s natural and acquired ability to resist microorganisms and the balance with the pathogenicity of microorganisms. When this balance is destroyed, some microorganisms that are not pathogenic in normal circumstances may invade the body and cause disease. This is the so called conditional pathogen.