Odontogenic Facial Cellulitis Caused by Haemophilus aphrophilus in a Pediatric Patient: A Culture-Guided Antibiotic Switch Following Extraoral Drainage A Case Report

<title>Abstract</title> <p> Background Odontogenic cellulitis is a common pediatric emergency that may progress rapidly if not managed appropriately. Successful treatment relies on prompt elimination of the source of infection, surgical drainage when indicated, and effective antimicrobial therapy. Although empiric antibiotics are routinely prescribed, treatment failure may occur because of antimicrobial resistance or infection with uncommon pathogens. <italic>Aggregatibacter aphrophilus</italic> , a member of the HACEK group and part of the normal oral microbiota, is rarely reported as a cause of odontogenic cellulitis in children. Case Presentation A 10-year-old previously healthy girl presented with a four-day history of painful swelling involving the chin and submental region, accompanied by fever (38°C). Clinical examination revealed diffuse, tender facial swelling without trismus. A grossly carious mandibular left second primary molar (FDI tooth 75) was identified as the source of infection, and a diagnosis of odontogenic cellulitis was made. The patient underwent extraction of the offending tooth together with incision and drainage of the abscess. Purulent material was collected for microbiological culture and antimicrobial susceptibility testing. Empiric treatment with amoxicillin-clavulanic acid and metronidazole was initiated; however, clinical improvement was limited. Culture demonstrated heavy growth of <italic>Aggregatibacter aphrophilus</italic> , which was resistant to amoxicillin but susceptible to amikacin and several other antimicrobial agents. Antibiotic therapy was subsequently changed to intravenous amikacin, leading to rapid resolution of fever, marked reduction in facial swelling, and significant clinical improvement within four days. Conclusions This case highlights the importance of considering uncommon pathogens in severe odontogenic infections that fail to respond to empiric antibiotic therapy. It also underscores the value of obtaining culture and antimicrobial susceptibility testing in selected cases to guide targeted treatment. Early surgical management combined with culture-directed antibiotic therapy resulted in a favorable outcome and supports the principles of antimicrobial stewardship in pediatric odontogenic infections. </p>