院内感染(又稱醫療照護相關感染)是醫療照護品質的重要指標之一，對患者及家屬而言，會增加其 身心痛苦、家庭負擔或承擔殘障或死亡，對醫療者而言，院内感染之發生，必然提高成本支出，病患住院曰數延長，病床週轉率降低，服務病患人次減少，甚至衍生醫療糾紛。執行院内感染管制工作，必需投入相當之人力、物力、時間及精神以採取適當的感染控制措施。一般而言，約有三分之一的院内感染屬於外源性感染，多是源自侵入性管路處置或手術傷口破壞表皮屏障導致感染，此類感染可以藉由有效的感染管制措施，如落實手部衛生及加強皮膚消毒等，來避免發生。另外約有三分之二的院内感染個案發生屬於内源性感染，因為抗生素使用造成的選擇性壓力使得原有之正常固有菌叢(normal flora)改變，經由局部黏膜缺損侵入形成血流轉移(bacterial translocation)，這類感染經常是源自於低免疫宿主病患，可能無法單純藉由感染管制措施來避免，必需同時減少抗生素使用及提升宿主免疫力才能減少發生機會。面對多重抗藥性菌造成之醫療照護相關感染增加，如何使用適當有效的藥物治療及感染管制措施已是目前醫療照護重要的課題。

Nosocomial infection (healthcare associated infection [HAI]) is an important quality indicator of medical care at hospitals. For patients and their families, HAI will increase their physical and mental suffering, families bear the burden or disability or death. For healthcare workers, the occurrence of HAI inevitably raises medical costs, prolongs the length of hospital stay and decreases bed turnover rate. Implementation of infection control efforts, must invest quite human, material, time and spirit in order to take appropriate infection control measures. Generally, about one-third of HAI are exogenous infections, mostly from invasive procedures or destruction of the barrier leading to infections. These exogenous infections can be avoided by effective infection control measures, such as strengthen the implementation of hand hygiene and skin disinfection. However, two-thirds of HAI are caused by endogenous flora because the high antibiotic selective pressure and bacterial translocation through damaged mucosa. These infections are often derived from patients with compromised immunity and usually unable to avoid by skin disinfection or hand hygiene. Rational use of antibiotics and improve the host immunity are necessary to reduce the occurrence of endogenous HAI. As the increasing trends of multidrug-resistant microbial infections at hospitals, the use of appropriate drug treatment and effective infection control measures is an important health care issue.