Bacterial Interactions with Host Epithelium In Vitro

During recent years there has been a resurgence of interest in the role that bacteria, both pathogenic and commensal, play in the pathogenesis and pathophysiology of disease. For example, antibiotics can be a useful therapy to relieve the symptomatology experienced by a cohort of patients with Crohn′s disease, a major class of inflammatory bowel disease (1 ). Traditionally, assessment of the impact of bacteria on the health status of an individual has focused on the role of their noxious products (e.g., lipopolysaccharide [endotoxin], exotoxins, and enterotoxins [e.g., cholera toxin, superantigens]) and recruitment and/or activation of immune cells. However, it is now clear that the direct interaction of bacteria with epithelial cells can mobilize intraepithelial signaling molecules, resulting in altered epithelial physiology. Studies using co-culture models of epithelial cell lines with bacteria have shown unequivocally that bacterial attachment to enterocytes affects a plethora of epithelial functions including vectorial ion transport, barrier function, and the production of immune mediators and chemokines; the latter response allowing participation in, and modulation of, mucosal immune reactions (2 ,6 ). Indeed, awareness that bacteria can directly affect the host cells to which they attach has led to a new discipline in microbiology-namely, cellular microbiology (7 ).