病原

维基百科，自由的百科全书

病原体是一个对可以引致疾病的生物的一个总称。病原体包括了：细菌、病毒和其他的生物，当中主要是细菌。

历史上首位確定病原体存在的，是1840年代的匈牙利的产科医生塞麥爾維斯（Ignaz Semmelweis）。他发现医院內由产科護士負責接生的貧窮產妇，她们的死亡率比相对较富有、由医生負責接生的產妇低几倍。他从他的观察中认定两者死亡率的差別，与环境的清洁有关连。

[编辑] 分類

[编辑] 主要病原

指的是一種病原，只要出現在正常、健康的個體中造成疾病cause disease as a result of their presence or activity within the normal, healthy host, and their intrinsic virulence (the severity of the disease they cause) is, in part, a necessary consequence of their need to reproduce and spread. Many of the most common primary pathogens of humans only infect humans, however many serious diseases are caused by organisms acquired from the environment or which infect non-human hosts.

[编辑] 伺機性病原

Organisms which cause an infectious disease in a host with depressed resistance are classified as opportunistic pathogens. Opportunistic disease may be caused by microbes that are ordinarily in contact with the host, such as bacteria or fungi in the gastrointestinal or the upper respiratory tract, and they may also result from (otherwise innocuous) microbes acquired from other hosts (as in Clostridium difficile enterocolitis) or from the environment as a result of traumatic introduction (as in surgical wound infections or compound fractures). An opportunistic disease requires impairment of host defenses, which may occur as a result of genetic defects (such as Chronic granulomatous disease), exposure to antimicrobial drugs or immunosuppressive chemicals (as might occur following poisoning or cancer chemotherapy), exposure to ionizing radiation, or as a result of an infectious disease with immunosuppressive activity (such as with measles, malaria or HIV disease). Primary pathogens may also cause more severe disease in a host with depressed resistance than would normally occur in an immunosufficient host.