Aerobic Pathogens and Antimicrobial Susceptibility in Odontogenic Infections: A One-Year Observational Study from...

Background and Objectives: Odontogenic infections are common emergencies in oral and maxillofacial surgery. They are typically polymicrobial, with aerobes guiding initial empirical therapy. However, regional data on their microbiology and resistance patterns in Romania are limited. This study aimed to characterize the aerobic microbial profile of odontogenic infections in Southwestern Romania and assess the antimicrobial susceptibility of isolated pathogens. Materials and Methods: A prospective observational study was conducted over 12 months at a tertiary referral hospital. Pus samples collected intraoperatively were cultured aerobically. Bacterial identification used biochemical methods and the VITEK 2 system. Antimicrobial susceptibility was determined by disk diffusion and automated MIC testing, interpreted according to EUCAST v13.0 (2023). Results: Of 110 patients, 96 (87.3%) yielded positive aerobic cultures, producing 97 isolates. Streptococcus spp. were predominant (49.5%), followed by coagulase-negative staphylococci (24.7%), Staphylococcus aureus (14.4%), Enterobacterales (7.2%), and Pseudomonas aeruginosa (3.1%). Streptococcus spp. remained susceptible to penicillin G (82.3%), amoxicillin-clavulanate (76.4%), and clindamycin (70.5%), but only 55.0% to erythromycin. Most S. aureus isolates were methicillin-susceptible (92.9%), while coagulase-negative staphylococci showed high methicillin resistance (59.3%) yet full susceptibility to linezolid, vancomycin, and teicoplanin. Enterobacterales were resistant to ampicillin (90%) and amoxicillin-clavulanate (65%) but remained susceptible to ceftriaxone (80%) and ciprofloxacin (85%). P. aeruginosa isolates were fully susceptible to piperacillin-tazobactam, ceftazidime, cefepime, and meropenem. Conclusions: This study provides regional data on aerobic pathogens in odontogenic infections. High resistance to penicillin and macrolides limits empirical use. Amoxicillin-clavulanate and clindamycin retain moderate activity, while glycopeptides, linezolid, and carbapenems preserved full efficacy. Surgical drainage remains central to management, and antibiotic therapy should be guided by local susceptibility patterns. These data provide baseline information to inform empirical therapy and stewardship efforts and highlight the need for multicenter studies including anaerobic and molecular analyses.