Aim: : To assess the most common micro-organisms causing odontogenic infections and the most effective antibiotic against. Materials and Methods: The study was conducted on 150 patients with maxillofacial infection. The pus sample was collected, cultured (aerobically and anaerobically) and stained for morphological study of the isolates. Antibiotic sensitivity test for the isolates were performed. Results: A total of 260 micro-organisms were isolated, Pure aerobes were identified in 54(36%) of

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... ases, pure anaerobes in 8(5%), mixed aerobes and anaerobes in 79(53%) andno pathogenic organism were isolated in 9(6%). Among the entire aerobic isolates, Ciprofloxacin and Amoxicillin/clavulanic acid were the most effective drug (100%) followed by Clindamycin (90%). The leasteffective drugs were amoxicillin (85%). Among the entire anaerobic isolates, Metronidazole was the most effective drug (100%) followed by Ciprofloxacin, Amoxicillin/clavulanic acid, Clindamycin (90%) each and Cefotaxime(80%). The leasteffective drug was amoxicillin (100%). Conclusion: The most common bacteria isolated were Staphylococcus spp., Streptococcus spp., Klebsiella spp., Prevotella spp., Peptostreptococcus spp. Ciprofloxacin, Amoxicillin/clavulanic acid and Clindamycin were the most effective drugs for all isolates. The least effective drug was amoxicillin.