In what situation is Candida albicans most likely to cause an opportunistic infection?

Candida albicans is a yeast that can be part of the normal flora of humans but can become pathogenic under certain conditions. An opportunistic infection occurs when the normally harmless organism exploits a change in the host's environment or immune status to cause disease.

When antibiotics are used, they can disrupt the normal microbiota of the host. These antibiotics often kill off competing bacteria, allowing Candida albicans to proliferate unchecked. Without this competition, the yeast can overgrow, leading to conditions such as thrush, vaginal yeast infections, or systemic infections, particularly in immunocompromised individuals.

The other situations mentioned, such as a healthy host or optimal environmental conditions, do not typically facilitate opportunistic infections by Candida albicans, as healthy individuals generally maintain a balance that prevents such overgrowth. High numbers of the pathogen alone do not guarantee an infection without the context of reduced competition or an altered host immune response.