Causes and consequences of bacterial adherence to mucosal epithelia during critical illness.

The interaction between host and pathogen during catabolic stress represents a dynamic battlefield, where the microbe's strategy to ensure its survival and multiplication come face to face with the repertoire of the host's immune system. From the microbe's point of view, the ICU offers the least optimal living condition, representing at times an outright holocaust for entire populations of fellow bacteria. This situation is especially true for intestinal bacteria, which can be exposed to all sorts of extreme conditions, such as starvation, turgor pressure, altered temperature, antibiotics, and osmolality changes. These conditions may act as environmental cues and elicit changes in bacterial gene expression that lead to effective coping responses. Starvation countermeasures can be especially strong signals for bacteria to follow chemical trails in search of nutrients. Harming the host is not the microbe's intent; its goal is to prevail. Injury to the host by a microbe struggling to survive is the inadvertent consequence of a threatening environment. This struggle between host and pathogen is particularly apparent at the mucosal surface, especially in the gastrointestinal tract, where microbes have enjoyed the leisurely life of a stable temperature and a constant food supply. The focus of this discussion is on one small aspect of the manner in which microbes ensure their survival during catabolic stress by attaching to host epithelial cells. The conditions and consequences of this process are discussed.