Francisella Tularensis

Francisella tularensis is a species of gram negative rods, which are non motile, non-spore forming aerobic bacteria, responsible for causing tularemia.

Portal of Entry
Humans are accidental “death-end” hosts, bitten by vectors or skin contact with wild animals. Rarely ingested in infected meat, producing gastrointestinal tularemia. Also are inhaled producing pneumonia
There is no person-to-person spread.

Pathogenesis

• Form ulcers at the site of entry.
• Survive in macrophages and are transported to reticuloendothelial system
• Granulomas are formed, followed by necrosis and abscess formation.
• Endotoxin is produced, but no exotoxin.

Virulence Factors
Lipopolysaccharide serves as endotoxin.

Predisposing Factors
•    Contact with wild animals
•    Bitten by vectors
•    Ingestion of infected meats
•    Immunocompromised persons
•    Cuts in skin

Clinical symptoms

Clinical symptoms depend upon the site of entry:

Handling infected animals

• Slow growing ulcer at the point of contact
• Swollen lymph nodes

Inhaled

• Sudden development of headache
• High fever
• Chills
• Body aches
• Fatigue

Ingested  

• Sore throat
• Abdominal pain
• Diarrhea
• Vomiting
• Eye infections
• Ulcers
• Pneumonia

Lab- Diagnosis

Microscopy
•    Gram negative rods
•    Non motile
•    Non- spore forming
•    Aerobic

Culture
Rarely done because of:-

• High risk of transmission of infection to lab workers
• Special cysteine- containing medium is required for growth is not easily available

Serological tests
•    Agglutination test with acute and convalescent phase serum sample.
•    Fluorescent –antibody staining
•    PCR