Penicillin concentration in saliva and its influence on bacterial interference

The aim of the investigation was to study the influence of various penicillin levels on the interference between alfa- and beta-streptococci based on antibiotic levels registered after oral intake of penicillin tablets. It was found that penicillin was released from ordinary sugar coated tablets already in the mouth resulting in concentrations in saliva above the MIC of most penicillin sensitive microorganisms during the first 2 min. This was followed by a decrease of the alfa-streptococcal flora. It was also shown that penicillin levels above the MIC of alfa-streptococci resulted in prolonged survival of beta-streptococci as compared to that noted at penicillin levels above the MIC of beta-streptococci but below that of the alfa-strains. At this latter level a synergistic effect between penicillin and interfering alfa-streptococcal strains could be demonstrated.