Figure 152-2.

Physical barriers.

A, Respiratory mucosa. A foreign body (an endotracheal tube, ETT) and/or positive pressure can irritate and injure the respiratory epithelium (ciliated cells; gray arrowheads denote denuded areas). Increased numbers of goblet cells (blue cells with inclusions) with decreased mucociliary clearance of the airway further increase the likelihood of infection (bacteria represented by purple spherical chains and blue/pink rods). B, Skin. Disruptions associated with trauma (venipuncture or heel stick), a peripherally inserted central catheter (PICC), a peripheral intravenous line (PIV), or tape-related abrasions compromise the skin barrier (bacteria represented by clusters of purple spheres and green rods). C, Gastrointestinal mucosa. Luminal bacteria (microbiota) are a valuable component of the mucosal barrier. The interaction between intestinal bacteria and intestinal epithelium is necessary for homeostasis and normal function of repair mechanisms. Disruption of this interaction, through the use of antibiotics or via stress to the organism (e.g., hypoxia or remote infection such as sepsis or pneumonia), results in loss of homeostasis and degradation of the intestinal boundaries with subsequent microbial translocation.