In the latest Case Record of the Massachusetts General Hospital, a 45-year-old man was admitted to the hospital because of diffuse, purple, blanching livedo over his arms and legs and signs of severe sepsis. Three days before presentation, the patient was bitten on his hands and forearms while bathing his dog. A diagnostic test result was received.
With respect to infections related to dog bites, one needs to consider organisms that colonize human skin and can be inoculated into the soft tissue through a dog bite. Staphylococcal and streptococcal species are common infecting organisms that can cause sepsis. Pasteurella multocida and Capnocytophaga canimorsus are considered normal oral flora in dogs.
• What are the characteristics of infection with Pasteurella multocida after a dog bite?
Infection with P. multocida, a gram-negative coccobacillus, can resemble the rapidly progressive soft-tissue infections caused by Streptococcus pyogenes, and there can be evidence of a wound infection hours after injury. P. multocida infection commonly causes cellulitis or abscesses; it can cause bacteremia, pneumonia, meningitis, and endocarditis, although these infections are less common. The organism is easy to culture and relatively sensitive to antibiotic agents.
• What are the manifestations of Capnocytophaga canimorsus infection?
C. canimorsus is a fastidious gram-negative bacillus that can cause overwhelming infection after a dog or cat bite. Patients with C. canimorsus infection present with symptoms ranging from cellulitis and local infection to meningitis, endocarditis, sepsis, and shock. Many cases of severe systemic C. canimorsus infection are associated with such underlying risk factors as splenectomy, alcoholism, cirrhosis, or immunosuppression, although in approximately 40% of cases, no identifiable risk factor is found. The end of the incubation period for C. canimorsus is typically marked by the abrupt onset of symptoms. Physical examination usually reveals a purpuric rash that can evolve to purpura fulminans and frank gangrene. The clinical manifestations of sepsis are caused by a profound inflammatory response that leads to microvascular injury and endothelial damage; if hypoperfusion and inflammation persist, then disseminated intravascular coagulation, gangrene, multiorgan failure, and death can occur. A patient’s clinical history is the key to the diagnosis of C. canimorsus infection, because the organism is difficult to culture and may take up to 14 days to identify.
Morning Report Questions
Q: What are the tenets of treating patients with sepsis?
A: The guidelines of the 2008 Surviving Sepsis Campaign include fluid resuscitation for intravascular volume expansion, with crystalloids for urine output (goal, >0.5 ml per kilogram per hour), optimization of mean arterial pressure at more than 65 mm Hg, maintaining central venous pressure at a goal of 8 to 12 mm Hg and central venous oxygen saturation at >70%. Lactic acid clearance should be monitored closely, because it indicates the success of the resuscitation in improving tissue perfusion. Patients should be pancultured and soon after arrival receive broad-spectrum antibiotics in addition to circulatory support.
Q: What is purpura fulminans?
A: Purpura fulminans is a syndrome most commonly related to an acute infectious process that is characterized by intravascular thrombosis and hemorrhagic skin infarction. It is rapidly progressive, and accompanied by disseminated intravascular coagulation and overall vascular collapse. The hallmark findings in acute infectious purpura fulminans are fever, hypotension, large purpuric skin lesions, and disseminated intravascular coagulation. Meningococcus infection is commonly associated with this condition, but it may also present in the setting of infection with varicella zoster virus, gram-negative bacilli, staphylococci, Rickettsia species, streptococci, and measles virus. Pathologic examination often reveals diffuse arterial and venous thrombosis. Microscopic foci of acute inflammation may be present in the vascular adventitia.