Effect of neuraminidase on receptor-mediated adherence of Streptococcus pneumoniae to chinchilla tracheal epithelium

The trachea whole organ perfusion technique was used to study the effect of the disruption of the Streptococcus pneumoniae neuraminidase nanA gene on bacterial adherence and alteration of the carbohydrate surface structures of respiratory epithelial cells. Six different lectin probes were used to examine alterations of the cell surface carbohydrates in chinchilla tracheal epithelium incubated in vitro with S. pneumoniae DeltaNA1, a neuraminidase-deficient mutant, or its D39 parent strain. The labeling pattern revealed that the binding of wheat germ agglutinin (WGA), Erythrina cristagalli lectin (ECL), peanut agglutinin (PNA), Bandeiraea simplicifolia lectin II (BSL II) and succinylated WGA was significantly increased in the luminal surface of the trachea in the D39-incubated cohort compared with the uninfected control, which indicated that GlcNAc and D-galactose residues were exposed. Concurrently, decreased labeling with Sambucus nigra agglutinin (SNA) indicated that there were few sialic acid residues remaining in the tracheal epithelium subsequent to incubation with D39. The DNA1 neuraminidase-deficient mutant, however, did not induce any significant changes in the lectin labeling patterns, which were comparable to those of the control cohort. Moreover, adherence data expressed as colony-forming units (CFU) of S. pneumoniae per millimeter of trachea indicated a significant decline in the ability of DeltaNA1 to adhere in vitro. We propose that products of the nanA gene have a significant impact on changes in the carbohydrate moieties in the tracheal epithelium, and may be responsible for the previously reported increased ability of the D39 parent to colonize the nasopharynx and invade the middle ear.