Escherichia coli RDEC-1 (serotype O15:H-) is a rabbit enteropathogen in which in vivo enteroadherence is both site specific and age related. To determine whether these differences could be related to mucins, we evaluated inhibition of binding of AF/R1 piliated RDEC-1 by mucins isolated from various segments of intestine of rabbits at different ages. Mucin was purified from intestinal crude mucus by cesium chloride serial ultracentrifugation. RDEC-1 was grown to promote the expression of hydrophobic mannose-resistant AF/R1 pili. Quantitation of in vitro bacterial binding was determined using a crystal violet colorimetric assay. In postweanling rabbits, inhibition of RDEC-1 binding by purified mucin derived from ileal segments (45.1 +/- 2.6%, mean +/- SEM) and proximal colonic segments (46.0 +/- 5.5%) was less than purified mucins derived from jejunal segments (70.0 +/- 2.0%) and distal colonic segments (71.0 +/- 3.7%, p < 0.05) of the intestinal tract. In all age groups, mucins derived from jejunal segments inhibited RDEC-1 binding to a greater level than mucins derived from ileal segments. In addition, inhibition of binding by mucin derived from proximal small intestine of postweanling rabbits (70.0 +/- 2.0%) was greater than that of weanling rabbits (55.2 +/- 3.5%, p < 0.05) with suckling rabbit inhibition (62.1 +/- 3.5%) between these two levels. We conclude that mucin inhibition of RDEC-1 adhesion is both age and region related and therefore may contribute to both age-related and site localization of bacterial infections of the intestinal tract.