Severe Implant-Related Maxillofacial Infection Associated with Citrobacter Species: A Case Report

This is a rare case of severe dental implant-related maxillofacial infection associated with Citrobacter spp. in the right submandibular space.An 85-year-old woman presented with facial swelling, extensive skin necrosis, and purulent discharge from a cutaneous fistula in the right mandibular region.Contrast-enhanced computed tomography revealed fenestration of the right mandibular lingual plate by a dental implant, with diffuse swelling and abscess formation in the submandibular space.The patient was immediately admitted, and empirical intravenous antibiotic therapy with cefoxitin (1 g t.i.d.) and metronidazole (500 mg t.i.d.) was initiated.Pus cultures identified Streptococcus constellatus, Citrobacter braakii, and C. freundii.Based on antimicrobial susceptibility testing, the antibiotic therapy was adjusted to ampicillin/sulbactam (3 g q.i.d.) and ciprofloxacin (400 mg b.i.d.).The patient improved significantly and was discharged on hospital day 7.The dental implant was removed under local anesthesia 3 d later and the infection continued to improve.This case highlights the rare involvement of Citrobacter spp. in implant-related maxillofacial infections and importance of microbial identification and susceptibility-guided antibiotic therapy in managing severe polymicrobial infections.