Infection
Infection is the invasion and multiplication of microorganisms in a host. It may occur without causing disease or symptoms.
Infectious agent: A microorganism or other biological agent capable of causing infection. Infections begin when an infectious agent reaches and establishes itself in a host.
Microorganism: A microscopic living organism, such as a bacterium, fungus, or protozoan. Many infections involve microorganisms that establish and multiply inside a host.
Microbiological culture: A laboratory method that grows microorganisms from a specimen to identify them or test their properties. Culturing can demonstrate viable organisms from a suspected site of infection.
Infestation: The invasion of a body surface or tissue by larger parasites, such as lice or mites. Clinical usage often distinguishes parasitic infestation from microbial infection.
Transmission (medicine): The movement of an infectious agent from one host or source to another. Transmission carries agents to new hosts, where infection may become established.
Host (biology): An organism that provides resources or shelter to another organism, including a parasite or pathogen. Infection describes an agent’s presence and multiplication within this organism.
Polymerase chain reaction: A laboratory technique that amplifies selected DNA sequences for detection and analysis. PCR can detect genetic material from infectious agents in patient samples.
Inflammation: A protective tissue response to injury, irritation, or harmful stimuli, including infections. Inflammation may result from infection, but can also arise without one.
Portal of entry: A route through which an infectious agent enters a host. The entry route shapes which tissues an agent can initially infect.
Colonization (biology): The presence and growth of microorganisms on or in a host without necessarily invading tissue or causing harm. Colonization can resemble infection, but does not necessarily involve tissue invasion.