Microbiology
Summary
Francisella tularensis is a facultative intracellular, gram-negative coccobacilli that causes the disease tularemia. F. tularensis is often present in rabbits, acting as its primary reservoir. Infection can arise from direct interaction with rabbits or more frequently, through indirect contact facilitated by a tick vector, particularly the Dermacentor tick. Any occurrence of F. tularensis must be reported to the CDC as it has a potential to be aerosolized, hence it could be utilized in bioterrorism.
Tularemia can lead to skin ulcers, necrosis, and painful lesions at the infection site, often caused by a tick bite. The bacteria can spread through the lymphatic system, affecting organs and causing local necrosis and granulomas. Notably, painful regional lymphadenopathy is a common presentation. Francisella can be effectively treated with aminoglycosides, such as streptomycin.
Lesson Outline
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FAQs
Francisella tularensis is a gram-negative, facultative intracellular coccobacillus that is highly infective and can cause a zoonotic disease known as tularemia. This disease can occur in many forms, ranging from skin ulcers to systemic and sometimes fatal illness.
Tularemia can be transmitted to humans through several pathways including through arthropod bites, mainly from the Dermacentor tick, and handling infected animals like rabbits. Ticks can acquire the bacterium by feeding on the blood of an infected animal and subsequently transmit it to humans during a blood meal. Rabbits can carry the bacterium and transmit it to ticks that feed on them or directly to humans when they are handled or consumed. Ingestion of contaminated water and inhalation of aerosolized bacteria are other modes of transmission.
Tularemia symptoms vary depending on how the bacteria entered the body. It often presents with an ulcer at the site of a tick bite or a rabbit wound followed by regional lymphadenopathy, which is swelling of the lymph nodes near the infection site. It also often involves the lymph system, progressing to granulomas with caseating necrosis. Other symptoms can include fever, fatigue, anorexia, and sometimes, pneumonia.
The most common treatment for tularemia is streptomycin, a type of aminoglycoside antibiotic. Alternative medications like gentamicin can also be used. Early diagnosis and treatment are important to prevent severe disease and long-term complications.
F. tularensis can be aerosolized and is highly infective, which has led to its classification as a Category A bioterrorism agent by the Centers for Disease Control and Prevention (CDC). An aerosolized release of F. tularensis can cause severe respiratory illness, which would be fatal without antibiotic treatment. Therefore, understanding about the bacterium and its characteristics are crucial in counter-bioterrorism efforts.
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