Overwhelming Sepsis after a Cat Bite

In mid-June, a 52-year-old man presented to the emergency department with fever, chills and a rapidly progressing erythema on his right hand without regional lymphadenopathy, a few days after being bitten by his domestic cat. The patient resided in a rural area and had a history of chronic alcohol consumption. The cat lived primarily outdoors and its immunization status was unknown. Pasteurella multocida cellulitis was suspected, oral amoxicillin-clavulanate was prescribed and the patient was discharged. Three days later, the cellulitis regressed completely but the patient sought medical attention for persisting fever and new-onset jaundice and dyspnea. On physical examination, he was hypotensive, exhibited hepatosplenomegaly and presented a centimetric necrotic ulcer on his right hand. The patient’s hematological results revealed leukopenia, thrombopenia and an elevated international normalized ratio. His biochemistry results revealed acute renal and liver failure. His chest radiograph was normal. The patient’s condition rapidly deteriorated to septic shock and multiple organ failure. He required mechanical ventilation, vasopressive support and renal replacement therapy. Intravenous piperacillin-tazobactam and vancomycin were empirically started; he was transferred to a tertiary care hospital the next day. On arrival to the intensive care unit, a septic workup was repeated and the patient’s hand ulcer was surgically debrided and tissue was sent for culture. Antibiotic treatment was switched to intravenous meropenem and vancomycin for sepsis of unknown origin. The patient developed further ascites. A percutaneous cholecystostomy was performed for suspected acalculous cholecystitis. The bile and the cloudy ascitic fluid were also cultured. Despite aggressive medical therapy, the patient’s condition failed to improve during the following two days and the family decided not to further pursue active treatments. At the time of the patient’s death, viral hepatitis serology and all bacterial cultures were negative. The following day, the aerobic blood cultures showed small Gramnegative coccobacilli. What is the diagnosis? DIAGNOSIS After four days of incubation, the plates of aerobic blood cultures grew small grey colonies on chocolate agar and on initial sheep blood agar. The same isolate was identified in all other specimens (necrotic ulcer, bile, ascites and endotracheal secretion). Laboratory technicians were instructed to handle the plates inside the biosafety cabinet because Francisella tularensis was suspected. The Gram stain of the colonies showed the same tiny Gram-negative coccobacilli. The organism was tetramethyl-oxidase negative, weakly catalase positive and nonmotile. The isolate was sent to the provincial reference laboratory, which confirmed the identification of F tularensis. Following the postmortem diagnosis, an investigation headed by the regional public health agency revealed that the cat was still in good health and its serology for F tularensis was negative. Other domestic and wild animals in the area also tested negative. There were no other cases of tularemia reported in the region during the rest of the summer. Nevertheless, informational pamphlets on tularemia were distributed to local small game hunters and warnings were published in regional newspapers to increase public awareness. DISCUSSION