Pasteurella multocida as an agent for osteoarticular infection

Description

A previously healthy and fully immunised female adolescent presented to the emergency department (ED) after being bitten on her hand by her domestic cat less than 12 hours prior. She came in with two deep, non-bleeding bite wounds from the cat’s teeth, along with pain, swelling and difficulty moving the ring finger of her right hand. X-rays of her hand showed no abnormalities. After cleaning and dressing the wounds, she was released with a prescription for oral flucloxacillin and instructions for outpatient wound care (figure 1). Two days later, the wounds showed no signs of improvement, so her antibiotic treatment was switched to amoxicillin/clavulanic acid.

Figure 1.

Bitten hand at the first emergency department admission.

After 2 weeks of ambulatory care, the patient returned to ED with malaise, fever, progressive aggravation of local inflammatory signs and frequent purulent drainage (figure 2). Laboratory results did not show elevated inflammatory parameters (10 280/uL leucocytes with 5310/uL neutrophils, C-Reactive Protein 0.6 mg/L and Erythrocyte Sedimentation Rate 11 mm/1st hour). Radiography (figure 3) indicated joint involvement, suggesting septic arthritis in the proximal interphalangeal joint (PIA).

Figure 2.

Inflammatory signs and purulent drainage after 2 weeks of oral antibiotherapy and dressing care.

Figure 3.

Radiography showing proximal interphalangeal joint erosion (white circle).

Surgical cleaning and debridement were carried out, and the patient began receiving intravenous ceftriaxone at 2 g per day, along with clindamycin at 600 mg every 8 hours. Following the identification of multisensitive Pasteurella multocida in the purulent discharge, antibiotic therapy was adjusted to benzylpenicillin at 200 000 U/Kg per day, administered every 6 hours. Despite the development of PIA ankylosis, the patient’s clinical condition continued to improve. After completing 3 weeks of intravenous antibiotics, the patient was discharged with a prescription for oral amoxicillin–clavulanate (7:1) at a dose of 50 mg/Kg per day.

The teenager continued her follow-up with the Department of Orthopaedics and Paediatric Infectious Diseases, where she underwent an MRI which confirmed the presence of osteomyelitis (figure 4). This resulted in a 3-month extension of the full course of antibiotic treatment. Over time, consecutive clinical and radiological assessments showed gradual improvement. At present, the patient does not experience any limitations to her daily activities, although she still has ankylosis in the PIA due to bone damage (figures 5–7).

Figure 4.

MRI showing postcontrast enhancement of the bone marrow of the distal slope of the proximal phalanx about persistent bone inflammation (white circle) and destruction of the distal aspect of the proximal phalanx of the fourth finger, with marked reduction of the interarticular space of the proximal interphalangeal joint (white arrow).

Figure 5.

Radiography 3 months postoperative showing proximal interphalangeal joint ankylosis (white circle).

Figure 6.

Palmar view of the bitten hand and finger after 4 months of antibiotic therapy.

Figure 7.

Dorsal view of the bitten hand and finger after 4 months of antibiotic therapy.

In conclusion, animal bites can be effectively managed with oral antibiotics after a thorough cleaning and debridement of the non-viable tissue and foreign bodies. In the event of an animal bite, the antibiotic treatment should be with amoxicillin-clavulanate 7:1 50mg/Kg/day (amoxicillin component) twice daily, for at least seven days. This therapy is used to address the aerobic and anaerobic microbial flora of the animal’s oropharynx. Clinicians should be particularly vigilant in case of cat bites as they tend to be deeper, due to their sharper teeth, which can cause deeper infections, particularly in sensitive areas, such as the fingers or the face.^{1 2}

Pasteurella multocida is a microrganism to be considered in cutaneous infections after an animal bite, especially when major inflammation is seen short time after the bite.³ These infections have poor functional prognosis and should be promptly treated, with intravenous antibiotics and surgical debridement to reduce the impact of these complications and long-term sequelae.^{3 4}

Learning points.

• When there is suspicion of an osteoarticular infection, it is important to promptly administer intravenous antibiotics and consider surgical intervention. These measures play a significant role in determining the prognosis and potential long-term consequences of the infection.

• When treating cases involving direct contact with animals, even in the absence of major inflammatory signs, it is important to take Pasteurella multocida osteoarticular infection into consideration.

• This case highlights the importance for healthcare providers to maintain a rapid investigation response and swiftly initiate treatment to prevent poor functional outcomes.

Ethics statements

Patient consent for publication

Consent obtained from parent(s)/guardian(s).