What is defined as the contamination or invasion of body tissue by pathogenic organisms?

The correct answer is infection because it specifically refers to the process in which pathogenic organisms, such as bacteria, viruses, fungi, or parasites, invade and multiply within the body’s tissues. This invasion typically results in the body’s immune response, which can lead to symptoms of illness.

Infection is characterized by the pathogen's ability to not only contaminate but also to actively reproduce and harm the host's tissues, leading to various health complications depending on the type of organism and the body's response. Understanding infections is crucial in fields such as medicine and public health, as it informs diagnosis and treatment strategies.

In contrast, inflammation refers to the body's response to injury or infection, which can occur as a result of an infection but is not the infection itself. Contamination implies the presence of pathogens but does not necessarily mean they are capable of causing disease. Immunization refers to the process of becoming immune or resistant to a disease, usually through vaccination, and is a preventive measure against infections rather than the state of having an infection.