Pneumolysin in pneumococcal adherence and colonization.

The universal and highly conserved production of pneumolysin, the major pneumococcal cytolysin, among clinical isolates of Streptococcus pneumoniae and the previously reported association of pneumolysin production with increased pneumococcal adherence to respiratory epithelium in organ cultures suggest that this toxin might be important for nasopharyngeal colonization. We confirmed that pneumolysin-deficient mutant pneumococcal strains had decreased adherence to respiratory epithelial cells in vitro compared with their isogeneic wild-type strains. However, neither early nor sustained colonization by type 14 S. pneumoniae in an established murine model was dependent on bacterial production of pneumolysin. We conclude that pneumolysin production is not a major determinant of successful nasopharyngeal colonization by pneumococci.