Infectious Diseases Chapter 150. A healthy person lives in harmony with the microbial flora that help protect from invasion by pathogens, usually microorganisms that have the capacity to cause disease. Microorganisms colonize body sites by a phenomenon known as tissue tropism, in which some tissues are colonized but others are not. The microbial flora comprises normal resident flora, which is found consistently and promptly reestablishes itself if disturbed, and transient flora, which may colonize the host for hours to weeks but does not permanently establish itself. Bacteria and fungi account for most of the commensal and symbiotic flora.
Pathogens occasionally are part of the normal flora.
Organisms in normal flora can cause disease, especially in patients whose defense barriers are disrupted. All rights reserved.