Persistence and spread of the orally-implanted bacterium Streptococcus sanguis between persons.

Transformant strains of streptomycin-resistant Streptococcus sanguis persisted 2.5 years after oral implantation in 6 out of 11 subjects. Natural transmission of these bacteria to spouses had occurred in 5 of the 6 infected subjects. At follow-up examinations, the median value of streptomycin-resistant Strep. sanguis per ml saliva was 226,000 c.f.u. in the infected subjects and 352,000 c.f.u. in their spouses. The median values of streptomycin-resistant Strep. sanguis as a percentage of the total Strep. sanguis c.f.u. count were 3.6 and 4.8 per cent in samples from vestibular mucosa, and 18.2 and 7.8 per cent in samples from the teeth of the infected subjects and their spouses, respectively.