Antibiotic Resistance of Streptococcus spp. Isolated from the Root Surface of Extracted Teeth to Penicillin V and Clindamycin Using E-Test

Background: Antibiotics are used to treat and prevent oral infections. Clindamycin and penicillin are widely used drugs in this field. Poor use of antibacterial agents causes the emergence of antibiotic-resistant bacteria. Objectives: The present study examined and compared the frequency distribution of resistance of streptococci isolated from the root surface of extracted teeth to penicillin V and clindamycin. This study was conducted in 2021 in Yazd, Iran. Methods: This was an analytical cross-sectional study performed in vitro. The samples were taken from the root surfaces of 50 teeth immediately after extraction and transferred to the laboratory in a transfer medium. After cultivation, isolation, and identification, the antibiotic resistance of isolates was measured by the E-test method. The data were analyzed using SPSS software (version 23). Results: Streptococci spp. were isolated from 46 samples (92%) without environmental contamination. The minimum inhibitory concentration (MIC) 50 and MIC 90 for penicillin V were 0.5 μg/mL and 1 μg/mL, respectively, and for clindamycin, 0.125 μg/mL and 0.19 μg/mL, respectively, which was significantly (P = 0.0001) lower for clindamycin. Intermediate sensitivity to penicillin V was 95.6%, and resistance to clindamycin was 21.8%. Conclusions: It seems that except in limited cases where there is resistance to clindamycin, this antibiotic is a more effective drug to control the bacteria in the mouth. However, in some cases, aerobic isolates showed intermediate sensitivity to penicillin V; instead, resistance to clindamycin was observed.