When body tissues are invaded by pathogenic bacteria, what can occur?

When pathogenic bacteria invade body tissues, an infection can occur as the harmful microorganisms multiply and disrupt normal cellular function. The body's immune response is activated to fight off these invading pathogens, which can lead to inflammation, pain, swelling, and other symptoms associated with infection.

In this context, while the body does have mechanisms to resist infections, the presence of pathogenic bacteria typically overwhelms these defenses, leading to an infection rather than a successful resistance. Severe allergies or accelerated healing are not direct outcomes of a bacterial invasion; instead, they pertain to other biological reactions or conditions that do not directly arise from the presence of pathogens. Thus, the correct choice highlights the direct consequence of bacterial invasion, which is the onset of an infection.