What term describes the contamination or invasion of body tissue by pathogenic organisms?

The term that describes the contamination or invasion of body tissue by pathogenic organisms is "infection." An infection occurs when harmful microorganisms, such as bacteria, viruses, or fungi, penetrate the body's defenses and begin to multiply in tissues, leading to damage and an immune response. This process often results in symptoms such as fever, pain, swelling, and redness as the body attempts to fight off the invading organisms.

In contrast, inflammation refers to the body's response to injury or infection, characterized by redness, heat, swelling, and pain; it is a symptom rather than the initial event of invasion. Sepsis is a severe and potentially life-threatening condition that arises when the body has an extreme response to an infection, leading to systemic inflammation and organ dysfunction. Contamination typically refers to the presence of unwanted substances or microorganisms in a sterile environment, which may or may not lead to an infection. This distinction clarifies why "infection" is the most accurate term in this context.