Alcaligenes rhinotracheitis of the turkey poult : bacterial adherence and virulence

Abstract

The binding of Alcaligenes fecalis to host respiratory epithelial cells and the host cell response to bacterial respiratory infection were examined in turkey poults using scanning and transmission electron microscopy, light microscopy, and adherence inhibition studies. A. fecalis specifically bound to ciliated epithelial cells. The surface to surface relationship among the bacteria, cilia, and microvilli was suggestive of a receptor-ligand interaction. The colonization of the ciliated cells led to the deciliation of the ciliated epithelium accompanied by mucin accumulation, extrusion of the epithelial cells, and cytoplasmic vacuolation. The nature of the host cell receptor was examined by blocking the receptor with specific carbohydrates or by destroying it with trypsin or sodium meta-periodate. The only effective inhibitor of adherence was sodium metaperiodate, indicating a role for monosaccharides in the host cell receptor. Bacterial plasmid content and cell surface properties were screened for their roles in the pathogenicity of various isolates of A. fecalis. Pathogenic isolates possessed one or more plasmids, while nonpathogenic isolates had no detectable plasmids. Cell surface monosaccharide content was evaluated using lectins to agglutinate bacteria with specific membrane carbohydrates. Monosaccharide content did not correlate with pathogenicity; however, a 50 K protein and a 24 K protein were detected in the outer membrane of pathogenic bacterial strains that was not present in nonpathogenic isolates. The results of this study establish the pathogenic relationship between A. fecalis and respiratory epithelial cells, and suggest that plasmid content and outer membrane proteins are determinants of virulence.