When oral administration is possible, penicillin agents are recommended for infectious endocarditis in the antibacterial prophylaxis method during dental treatment. If the patient is allergic to penicillin, first-generation cephem agents are recommended. As of 2003, the antibacterial activities of cepfalexin（CEX） and cefaclor（CCL） against oral Streptococci from odontogenic infections were as follows：CEX –MIC90 was ＞ 100μg/mL；CCL– MIC90 was 100μg/mL. We measured the antibacterial activities of CEX, CCL, cefditoren and amoxicillin（AMPC） with respect to the 50 respective shares of the Streptococcus mitis group and the Sterptococcus anginosus group for each fiscal year from 2005 to 2015.
The annual changes of MIC90 value of each agents for S. mitis group were found to be as follows：For CEX, it was 16〜64μg/mL； for CCL, 4〜32μg/mL；for AMPC, 0.12〜0.5μg/mL. The annual changes of the MIC90 value of each agent in the S. anginosus group were found to be as follows：For CEX, it was 8〜16μg/mL；for CCL, 4〜8μg/mL；for AMPC, 0.12〜0.25μg/mL.
