Impact of phenoxymethylpenicillin, erythromycin, clindamycin and doxycycline on Streptococcus salivarius in the oropharynx.

Streptococcus salivarius plays a role in the normal oropharyngeal resistance to colonization with group A streptococci. Suppression of Str. salivarius may increase the risk of colonization. Ten subjects were given phenoxymethylpenicillin, ten were given erythromycin, ten were given clindamycin and ten were given doxycycline for seven days. The numbers of Str. salivarius in the oral cavity were determined before, during and after the administration periods. Phenoxymethylpenicillin and doxycycline only slightly suppressed the numbers of Str. salivarius, while erythromycin and clindamycin markedly decreased the numbers. In four and five subjects respectively, Str. salivarius could no longer be isolated after seven days of the drug administration.