Antibiotic resistance of pathogenic bacteria from odontogenic infections in Taiwan

The purpose of this study was to evaluate the susceptibility of facultative and anaerobic odontogenic infectious flora to various antibiotics. We assessed 178 bacterial strains isolated from 74 patients with odontogenic infections. The E-test was used to determine susceptibility. The microbial flora was predominantly facultative gram-positive organisms and anaerobic gram-negative bacilli. The results of antimicrobial susceptibility test showed that ampicillin resistance was found with a very high level of minimum inhibitory concentration (MIC) in approximately one third of Fusobacterium nucleatum, Prevotella intermedia, Peptostreptococcus micros, and Eikenella corrodens isolates (MIC > or = 8 microg/mL). Greater activity was generally noted with amoxicillin than with ampicillin, but even beta-lactamase inhibitor incorporated amoxicillin showed resistance in more than 10% of all groups except viridans group streptococci and Porphyromonas gingivalis. Tetracycline and erythromycin were considerably less active against the majority of the tested bacterial strains, while minocycline and doxycycline exerted strong antimicrobial activity and could inhibit strains grown at a very low concentration. Among all the tested antibiotics, travofloxacin appears to be a promising drug expressing the highest activities (MIC90 < or = 1 microg/mL), and was regarded as a potent bactericidal drug in odontogenic infections.