A 5-year-old girl presents to the emergency room due to difficulty walking. She has been complaining of pain in her right leg for the last few days. Her neighbor’s cat bit her last week and her parents attributed the pain to her healing bite. At the time of the bite, they cleaned the wound and irrigated it with sterile saline water from a first aid kit. She has no medical history and has never been hospitalized. Her temperature is 102.2°F (39°C), blood pressure is 118/78 mmHg, pulse is 90/min, respirations are 21/min, and pulse oximetry is 99% on room air. The open wound remains present on the thigh with surrounding erythema and edema. MRI is consistent with osteomyelitis. Which of the following is the most appropriate next step in management?
Doxycycline
Ampicillin and sulbactam
Amoxicillin and clavulanate
Flucanozole
Ampicillin and sulbactam
This young girl with a recent history of a cat bite and difficulty walking most likely has likely Pasteurella multocida osteomyelitis. Empiric IV antibiotic therapy with ampicillin-sulbactam is the most appropriate initial management.

Pasteurella multocida is a gram-negative rod that is associated with cat and dog bites. Infection can lead to cellulitis and osteomyelitis. Treatment of minor infection is with amoxicillin-clavulanate; however, patients suspected of having osteomyelitis should be treated empirically with IV antibiotics (e.g., ampicillin and sulbactam) and taken for biopsy/culture to identify the pathogen. Antibiotics can then be narrowed down accordingly. Patients will often require between 4-8 weeks of antibiotic treatment. MRSA coverage may initially be started and tapered later once cultures result.

Mollitt reviews the evidence regarding the microbiology of various injuries. He discusses how Pasteurella multocida is a common complication of animal bites. He recommends early effective antibiotic treatment.

Incorrect Answer:
Answer A: Amoxicillin and clavulanate can be used to treat Pasteurella infection. Patients with osteomyelitis should not be treated with oral antibiotics initially, in particular, when there are systemic manifestations as is present in this patient. IV antibiotics such as ampicillin and sulbactam are the mainstay for empiric osteomyelitis treatment after an animal bite in a patient with systemic manifestations.

Answer C: Doxycycline is used to treat uncomplicated chlamydia infections. Gonococcal osteomyelitis may present in sexually active individuals and may be associated with septic arthritis. Sexually active patients may be suspected of having this disease.

Answer D: Fluconazole is an antifungal that is used to treat Candida osteomyelitis. Candida osteomyelitis would be highly unusual in patients with no other risk factors. Instead, this disease is more common in immunodeficient patients or those who use IV drugs.

Answer E: Vancomycin is used for MRSA infections. Although S. aureus is the most common overall cause of osteomyelitis, this patient with a recent animal bite most likely has Pasteurella infection and this organism should be covered accordingly.

Bullet Summary:
Patients with suspicion of Pasteurella osteomyelitis infection after an animal bite should be treated with empiric IV antibiotics such as ampicillin and sulbactam.