Background/aims: Systemic dissemination of oral bacteria to distant body sites may be the cause of focal infections. The unsuitable use and overexposure to antimicrobial therapy in clinical dental practice may contribute to the worldwide problem of antimicrobial resistance. The aim of this study was to determine the susceptibilities of streptococci isolated from the bloodstream after dental extractions against penicillin, ampicillin, amoxicillin, erythromycin, clindamycin, and a new fluoroquinolone, moxifloxacin.
Patients and methods: Eighty-four patients who required dental extractions were studied. Venous blood samples were collected from each patient at baseline (before dental manipulation) and 30 s after dental extractions. The samples were processed in the Bactec 9240. The isolated bacteria were identified by conventional microbiological techniques. The antimicrobial susceptibility of 81 streptococci was determined by the E-test method. The NCCLS performance standards were followed.
Results: 88.9-92.5% of the streptococci were sensitive to beta-lactam agents tested with a minimum inhibitory concentration (MIC)(90s) ranging from 0.094 to 0.19 mg/l. The resistance to erythromycin and clindamycin was 40.8% (MIC(90HR) = 256 mg/l) and 21% (MIC(90HR) = 256 mg/l), respectively. The MIC(90) to moxifloxacin was 0.125 mg/l.
Conclusion: Most of the streptococci isolated from the bloodstream after dental extractions were susceptible in vitro to penicillin, ampicillin, and amoxicillin. The high percentage of streptococci resistant to erythromycin and clindamycin could restrict their usefulness as prophylactic drugs. All the isolates showed a low MIC of moxifloxacin in vitro, making it a promising antimicrobial alternative for the prevention of streptococcal focal infections associated with certain dental manipulations, when the administration of beta-lactam agents is not indicated.