Abstract
A strain of viridans Streptococcus from the pharynx of a 6-year-old healthy girl was found to be inhibitory to Neisseria meningitidis, employing both an agar overlay technique and a cross streaking technique. The results showed that the viridans Streptococcus was also able to inhibit the growth of Pseudomonas aeruginosa, Salmonella typhi, Acinetobacter calcoaceticus and Neisseria lactamica, but was unable to inhibit the growth of Shigella sp. and E. coli. These results suggest that viridans streptococci from the normal pharyngeal microflora may play an important role in regulation of the ecology of the pharynx and upper airways.