INTRODUCTION:Pasteurella multocida is an organism commensal to the saliva of animals. It’s virulence is extremely variable and can cause life threatening disease in humans. We report the first case of empyema necessitans secondary to disseminated Pasteurella multocida infection in a man exposed to cat saliva through open leg wounds.
CASE PRESENTATION:A 55 yo man with a history of recently diagnosed non small cell lung cancer and diabetes with neuropathy presented to the hospital with 2 weeks of worsening chest pain and dyspnea. He reported no pets and denied recent travel outside of Boston. He was found to be febrile, hypotensive and mildly hypoxemic. Physical exam was notable for absent breath sounds on the right, a 5 × 7 cm fluctuant mass in the right subscapular area and bilateral lower extremity skin ulcerations. Computed tomography (CT) of the chest revealed a large loculated right pleural process with evidence of chest wall invasion (see figure 1). Chest tube thoracostmy was performed and 1.2 liters of purulent material was drained. Pleural fluid analysis revealed a pH of 7.0, lactate dehydrogenase of 8,000mg/dL and glucose of 3mg/dL. Grams stain showed numerous gram negative coccobacilli (see figure 2). Within 10 hours of admission, 2 blood cultures were positive for gram negative coccobacilli. The organism was identified as a mucoid strain of Pasteurella multocida. On further questioning the patient reported that his peripheral neuropathy had advanced to the point where “ I couldn’t feel my neighbor’s cats licking my legs”.
DISCUSSIONS:Pasteurella multocida infection from animals to humans represents a common and clinically relevant group of infectious disease syndromes. Classically, the innoculation is in the form of a bite from a cat or a dog. Our case is unique for multiple reasons. First, it is the only reported case to date of this organism causing dissemination with pleural infection and chest wall invasion. Secondly, this particular strain, with it’s mucoid capsule, represents an example of the variable virulence of this organism. Finally, our patient aquired the infection by way of his lower extemity neuropathic wound exposure to a cat’s saliva. The capsular composition is an important determinant of the virulence of the Pasteurella species. Strains identified by capsular composition have been shown to cause disease syndromes ranging from flu-like illness in humans to hemorrhagic septicemia in animals (1). This case emphasizes the importance of specific medical history taking and the variable virulence factors associated with zoonotic organisms in compromised hosts. The patient’s pleural space was drained with a large bore chest tube for 2 weeks and he was treated with intravenous ceftriaxone. His clinical status slowly improved and he did not require decortication. He was transferred to a rehabilitation facility and eventually discharged home.
CONCLUSION:Pasteurella multocida infection in humans can be severe and life threatening depending on the host and capsular components of the organism. Our case represents the first report of empyema necessitans from dissemination and pleural infection of a Pasteurella species.
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