[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fXT8fBprJKjj6uzTS2PHBlsE82MwwTBq2K0SmDLUEVK4":32,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":47},[4,8,12,16,20,24,28],{"title":5,"slug":6,"path":7},"About Microbeonline.com","about-microbeonline-com","\u002Fabout-microbeonline-com\u002F",{"title":9,"slug":10,"path":11},"About Me","about-me","\u002Fabout-microbeonline-com\u002Fabout-me\u002F",{"title":13,"slug":14,"path":15},"Advertise with Us","advertise-us","\u002Fadvertise-us\u002F",{"title":17,"slug":18,"path":19},"Privacy Policy","privacy-policy","\u002Fprivacy-policy\u002F",{"title":21,"slug":22,"path":23},"Abbreviations","abbreviations","\u002Fabbreviations\u002F",{"title":25,"slug":26,"path":27},"Microbes","microbes","\u002Fmicrobes\u002F",{"title":29,"slug":30,"path":31},"Books","recommended-books","\u002Frecommended-books\u002F",{"type":33,"data":34},"blog",{"slug":35,"title":36,"description":36,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":39,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"body":43,"faq":44,"tags":45,"related":46},"francisella-tularensis-properties-pathogenesis-lab-diagnosis","Francisella tularensis: Properties, Pathogenesis, Lab Diagnosis",null,"Acharya Tankeshwar","2020-10-13","2025-12-29",false,"bacteriology","*Francisella tularensis* causes life-threatening infections in animals (rabbits, hares, and rodents) and people (zoonotic disease). It is also known as ‘Rabbit Fever’ or ‘Deer Fly fever.’\n\n![Francisella tularensis basic feature](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FFrancisella-tularensis-.jpg)Figure: *Francisella tularensis* basic feature\n\n## Properties ofFrancisella tularensis\n\n- Causes **highly infectious** (as few as 10 organisms can cause disease and the organism can enter the human body through skin, eyes, mouth, or lungs) but treatable (can be treated successfully with antibiotics).\n- **Agent of bioterrorism**: Because of its highly infectious nature *F. tularensis* is currently classified as a **category A agent of bioterrorism**.\n- Bacterial culture of tularemia should be carried out in a **biosafety level 3 (BSL3)** laboratory.\n- **Gram-negative coccobacillus**\n- Non-motile\n- Non-[spore](\u002Fbacterial-spores\u002F) forming\n- Facultative intracellular bacteria\n- Aerobic\n- Fastidious bacteria (requires **cysteine enriched medium** for growth)—Cysteine enriched chocolate agar, BCYE agar, and CHAB agar (cysteine heart agar with blood).\n\n![ - Francisella tularensisidentification flowchartImage source: Laboratory Response Network (LRN)](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FTularemia-identification.png)Figure: *Francisella tularensis i*dentification flow chart Image source: Laboratory Response Network (LRN)\n\n## Pathogenesis\n\n### Mode of Transmission\n\n**Source:** It persists in contaminated environments, insects, and animal carries.\n\n![](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FAmerican-dog-tick.jpg)![](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Flone-star-tick.jpg)### Transmission routes\n\n- **Bite** of blood-sucking insects such as **tick and deer fly**\n- Skin **contact** with infected animals\n- **Ingestion** of contaminated water\n- **Inhalation** of contaminated aerosols or agricultural and landscaping dust\n- **Laboratory exposure:** In the cases of unanticipated events, laboratory workers may get exposed and acquire infection with *F. tularensis* while subculturing positive broth blood cultures, performing Gram’s staining, or examining agar plates\n\n### Prevalence\n\n*F. tularensis* has **four subspecies**: *tularensis, holarctica, novicida,* and *mediasiatica*. The first three species are found in North America whereas subspecies mediasiatica is found in **central Asia**. Subspecies **tularensis is the most common and the most virulent among all.** It has been isolated only from North America, which accounts for more than 70% of cases.\n\nIncreasing number of cases due to other subspecies have been reported from the Scandinavian countries, Eastern Europe and Siberia.\n\n### Virulence Factors\n\nOnce *F. tularensis* is engulfed by immune cells (macrophages) that routinely kill bacteria, it replicates and evades parts of the immune system using an array of virulence factors:\n\n![](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FLife-cycle-of-Tularensis.jpg)- Capsule (anti-phagocytic in nature)\n- The outer membrane (LPS layer) helps to thwart innate immune response as it evades recognition by Toll-Like receptors (TLR)\n- Type IV Pili (adherence)\n- Acid phosphatase: Prevents the fusion of phagosome with the lysosome.\n- Siderophores: acquisition of iron\n\n### Clinical Manifestations\n\nTularemia symptoms usually appear within 3-5 days of infection, but may also appear up to 15 days later. Tularemia is characterized by various clinical syndromes depending on how the person was infected.\n\n**Main forms of the disease are:**\n\n#### Ulceroglandular tularemia\n\nIt is the most common form, (75-85% of total cases), characterized by an ulcerative lesion at  the site of inoculation, with regional lymphadenopathy (armpit or groin.)\n\n#### Glandular tularemia\n\nIt presents with swollen lymph nodes (without ulcer)\n\n#### Pulmonary tularemia\n\n- It can result from aerosol inhalation (laboratory workers) or can spread to the lungs following bacteremia if other forms of tularemia are left untreated.\n- Symptoms include cough, chest pain, and difficulty breathing.\n- Most serious forms of tularemia\n\n#### Oropharyngeal tularemia\n\nIt occurs following the ingestion of contaminated undercooked meat. It is characterized by membranous pharyngitis with cervical lymphadenopathy.\n\n#### Oculo-glandular tularemia\n\nThis form occurs when the bacteria enter through the eye. It is characterized by purulent conjunctivitis with preauricular lymphadenopathy.\n\n#### Typhoid-like illness\n\nIt presents with the standard, nonspecific febrile (fever) symptoms, but without a known route of infection (via the skin, eye, ingestion, or inhalation)\n\n## Laboratory Diagnosis\n\nDifficult to diagnose because it’s a rare disease with nonspecific signs and symptoms. Diagnosis may rely on epidemiologic evidence (e.g., history of mowing the lawn in an endemic area)\n\n### Specimen\n\nUlcer scrapings, lymph node biopsy, gastric washings, sputum, and blood.\n\n### Culture\n\nIsolation is very difficult as *F. tularensis* is highly fastidious\n\nIt needs special media such as:\n\n- BCG agar (blood cysteine glucose agar)\n- CHAB agar (cysteine heart agar supplemented with 9% heated sheep blood).\n\n![ - F. tularensisin cysteine enriched chocolate agar](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FChocolate_agar_1.jpg)Figure: *F. tularensis* in cysteine enriched chocolate agar\n\nSpecimens are inoculated onto the media and incubated at 37oC for 2-4 days aerobically as *F. tularensis* is an obligate aerobe.\n\nColonies are blue-gray, round, smooth, and slightly mucoid with small zone of alpha-hemolysis.\n\nSafety precautions such as biosafety level III must be used to handle clinical specimens to avoid the risk of laboratory-acquired infections.\n\n#### Identification\n\n- *F. turalensis* is a small gram-negative coccobacillus with bipolar appearance, non-motile and capsulated.\n- It is weakly catalase positive, oxidase negative and H2S positive\n- It produces acid but no gas from glucose, maltose and mannose.\n- Direct fluorescent antibody tests can be done with commercially available antisera, directly from the culture colonies for subsequent identification.\n\n### Antibody detection\n\nIt is the mainstay of diagnosis as isolation is difficult. Agglutination test (latex and tube agglutination) and ELISA formats are available.\n\n### Molecular Diagnosis\n\nPCR assay has been used to detect *F. tularensis* specific genes encoding the outer-membrane proteins. It can also differentiate subspecies.\n\n## Prevention & Treatment\n\nSteps to **prevent** tularemia include:\n\n- Using insect repellent\n- Wearing gloves when handling sick or dead animals\n- Avoiding mowing over dead animals\n\n**Treatment**\n\nStreptomycin, gentamicin, doxycycline, and ciprofloxacin are used to treat tularemia. Treatment usually lasts 10 to 21 days depending on the stage of illness and the medication used.\n\n**References**\n\n1. Madigan Michael T, Bender, Kelly S, Buckley, Daniel H, Sattley, W. Matthew, & Stahl, David A. (2018). [Brock Biology of Microorganisms](https:\u002F\u002Famzn.to\u002F2USOj0v) (15th Edition). Pearson.\n2. [Color Atlas and Textbook of Diagnostic Microbiology](https:\u002F\u002Famzn.to\u002F2vRkUvk), Koneman, 5th edition",[],[],[],[48,54,61,66,70,74,79,84,88,92],{"slug":49,"name":38,"description":50,"image":51,"body":52,"postCount":53},"acharya-tankeshwar","Editor-in-chief","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Ftankeshwar-acharya-author-microbeonline.jpg","***Tankeshwar Acharya, MSc (Medical Microbiology)***\n\n*Tankeshwar Acharya is an Assistant Professor in the Department of Microbiology at Patan Academy of Health Sciences (PAHS), Nepal, where he has been teaching and practicing clinical microbiology for over 14 years. He is the founder of Microbe Online, one of the leading free microbiology education resources on the web, covering bacteriology, mycology, parasitology, immunology, and clinical laboratory diagnostics written from direct experience in both the classroom and the diagnostic laboratory.*",433,{"slug":55,"name":56,"description":57,"image":58,"body":59,"postCount":60},"ashma-shrestha","Ashma Shrestha","SEO Copywriter and Science Communicator\nKathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fashma-shrestha.png","Ashma Shrestha holds a Master of Science in Medical Microbiology from the Institute of Science and Technology (IOST), Tribhuvan University, Nepal, where she developed a strong foundation in virology, molecular biology, and diagnostic microbiology.\n\nShe now works as an SEO Copywriter at Resolution Digital, where she combines her scientific training with research-driven content strategy. She is certified in Google Analytics and Google Business Profile (GBP), and brings a data-informed approach to science communication writing content that is not only accurate but structured to reach and serve the students who need it most.\n\nAt microbeonline, Ashma contributes articles primarily in virology and molecular biology, areas she finds most compelling for their mechanistic depth and their growing clinical relevance. Her writing reflects the same standard the site is built on: factual rigor, clear explanation of the *why* behind microbiology concepts, and content that helps students move from memorization to genuine understanding.\n\nShe is passionate about making complex microbiological concepts accessible without sacrificing accuracy; a skill that sits at the intersection of her scientific training and her professional work in content and SEO.",81,{"slug":62,"name":63,"description":64,"image":37,"body":37,"postCount":65},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor",32,{"slug":67,"name":68,"description":64,"image":37,"body":37,"postCount":69},"samikshya-acharya","Samikshya Acharya",20,{"slug":71,"name":72,"description":64,"image":37,"body":37,"postCount":73},"alisha-tripathi","Alisha Tripathi",6,{"slug":75,"name":76,"description":77,"image":37,"body":37,"postCount":78},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",10,{"slug":80,"name":81,"description":82,"image":37,"body":37,"postCount":83},"guest-author","Guest Author","Guest Author \u002F Contributor",2,{"slug":85,"name":86,"description":64,"image":37,"body":37,"postCount":87},"srijana-khanal","Srijana Khanal",18,{"slug":89,"name":90,"description":82,"image":37,"body":37,"postCount":91},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":93,"name":94,"description":64,"image":37,"body":95,"postCount":96},"nisha-rijal","Nisha Rijal","**Nisha Rijal** is a microbiologist and quality assurance specialist. She served for nearly 12 years as a microbiologist at the National Public Health Laboratory (NPHL), Nepal's national reference laboratory, and continues to work as a consultant microbiologist in international public health organization. ",51]