A Case of Persistent Pasteurella multocida Cellulitis Complicated With Large Endocarditis Vegetation

In the realm of infective endocarditis, a distinct and infrequent player emerges - <i>Pasteurella multocida</i>, an organism more commonly associated with zoonotic infections, now warranting careful consideration in this unique case report. <i>P</i> <i>.</i> <i>multocida</i> is a Gram-negative, facultative anaerobic cocco-bacillus and a common member of the oral bacterial flora of cats and dogs. In humans, it commonly causes skin and wound infections after bites and scratches. Disseminated <i>P</i> <i>.</i> <i>multocida</i> infection seeded into the heart valve is very rare and has only been reported in about one case per year worldwide with only 42 cases found in the literature and only five cases reported to have underlying liver cirrhosis as in our case. This is a case of a 73-year-old female with a past medical history of Child-Pugh B liver cirrhosis secondary to primary biliary cholangitis with portal hypertension, splenomegaly, pancytopenia, severe aortic stenosis, and paroxysmal atrial fibrillation presented to hospital with generalized weakness, fever, and new lower extremity rash 48 hours after last dose of antibiotic. She had recent hospitalization for left lower extremity cellulitis and<i> P. multocida</i> bacteremia and received 14 days of high-dose oral amoxicillin-clavulanate with negative blood culture prior to discharge. She occasionally helps her son to feed his cats and dog whenever he travels. She was readmitted and a repeat blood culture showed <i>P. multocida</i>. Transthoracic echocardiogram showed a 1.9 cm × 1 cm mobile mass attached to the anterior mitral valve leaflet, which was new compared to the prior study obtained during her first admission. She was not a suitable candidate for valve surgery due to her comorbidities. <i>P.</i> <i>multocida</i> was found to be susceptible to penicillin, ampicillin, levofloxacin with negative beta lactamase. Her cellulitis, fever, and bacteremia eventually resolved with intravenous antibiotics. She was ultimately discharged with a two-week course of intravenous ceftriaxone, continued with oral levofloxacin to complete six weeks of total treatment, and followed by long-term penicillin suppression. In this case report, we delve into a rare and intriguing clinical presentation of <i>P</i> <i>.</i> <i>multocida</i> endocarditis. Our patient is the second reported case which showed complication of native mitral valve endocarditis even in the setting of bacteremia resolution. This report sheds light on the challenging diagnosis and management of this uncommon yet clinically significant condition, highlighting the importance of vigilant and prompt intervention in cases of infective endocarditis with atypical causative agents.