F. tularensis subspecies exhibit abroad host ranges. Diseases caused by this species is sub-divided into several forms, based on clinical presentation.

1. Francisella Tularensis
Samras. A
II B. Sc. Microbiology
PG & Research Department of Biotechnology and
Microbiology
National College [Autonomous]
Tiruchirappalli, Tamil Nadu- 620001, India
Francisella tularensis

2. History
1. This bacteria origin in tulare region in California .
2. It’s was first isolated by Geroge Walter McCoy (1876-1952) of US plague lab in San
Francisco in 1912 .
3. In 1922 Edward Francis (1872-1957) announced B. tulerinsis was the causative
agents of Tularensis .
4. But he couldn’t recognise the origin of the bacteria.
5. Hechiro Oharo discovered the origin of bacterial spread from rabbits in Fukushima
region of Japan.

3. MORPHOLOGY:
 Capsulated
 Gram Negative Bacilli
 Non Motile
 0.3 – 0.7 µm x 0.2 µm in size
 Transparent colonies
 Incubation for 3- 5 days

4. Mode of transmission :
Mostly rabbit and other rodents are spreaders
BIOTYPES :
Based on virulence and epidemilogocal behaviour, 2 types of biotypes were
recognized.
 HIGHLY VIRULENCE STRAINS ARE FOUNDS ONLY IN NORTH AMERICA .
 LOW VIRULENCE STRAINS ARE FOUND ONLY IN Europe and Asia

5. Lab Diagnosis:
Specimen:
• Scrapings from infected ulcers, lymph node biopsies,
and sputum, whole blood.
• To minimize the loss of viable organisms, samples
should be transported to the laboratory within 24
hours.
• If specimens are to be held longer than 24 hours,
specimens should be refrigerated in Amie’s transport
medium.
• F. tularensis should remain viable for up to 7 days
ambient temperature in Amie’s medium.

6. Direct Microscopy
• Gram negative coccobacilli are seen in Gram
staining procedure.
• A more sensitive and specific approach is direct
staining of the clinical specimen with fluorescein
labeled antibodies directed against the organism.
• Fluorescent antibody stains and immune-
histochemical stains are commercially available
for direct detection of the organism in lesion
smears and tissues and are typically available in
reference laboratories.

7. Francisella tularensis is a poorly staining, Gram-negative, non-motile,
coccobacillus bacterium, ranging from 0.2 by 0.2 to 0.7 µm in size

8. Culture:
 The organism is strictly aerobic and is enhanced by enriched media
containing sulfhydryl compounds (cysteine, cystine, thiosulfate or
IsoVitaleX) for primary isolation.
 Two commercial media for cultivation of the organism are
available: glucose cystine agar and cystine-heart agar, both require
the addition of 5% sheep or rabbit blood.
 They are slow-growing organisms and require 2 to 4 days for
maximal colony formation.
 They are weakly catalase positive and oxidase negative.
 The identification is confirmed by demonstrating the reactivity of
the bacteria with specific antiserum (i.e., agglutination of the
organism with antibodies against Francisella).

9. (A) buffered charcoal yeast extract; (B) chocolate agar medium;
(C) sheep’s blood agar; (D) cysteine heart agar.

10. Antibody detection :
Serum antibody detection is useful for all forms of
tularemia.
After the initial specimen, a convalescent sample
should be collected at 14 days and preferable up to
3 to 4 weeks after the appearance of symptoms.
Tularemia is diagnosed in most patients by
observing the increasing titer values of antibodies
during the illness or a single titer of 1:160 or
greater.

11. Molecular methods:
 Conventional and real-time polymerase chain
reaction (PCR) assays have been developed to detect
F. tularensis directly in clinical specimens.
 Of significance, several patients with clinically
suspected tularemia with negative serology and
culture had positive reaction in PCR.

12. Pathogenicity:

Francisella tularensis enters the respiratory tract and (2) the lamina propria of the respiratory bronchioles
via M cells; (3) Digested antigen is taken up by dendritic cells; the dendritic cells travel to regional lymph
nodes and present F. tularensis antigens to T-helper 1 cells; (4) T-helper 1 cells proliferate; they may return
to site of initial infection; (5) restimulation by local antigen presenting cells results in interferon-γ
production and macrophage activation; (6) Failure to clear the F. tularensis results in granuloma formation.

13. Clinical diagnosis:
F. tularensis subspecies exhibit a broad host ranges. Diseases caused
species is subdivided into several forms, based on clinical
presentation, namely:
 typhoidal (systemic signs of sepsis)
 pneumonic (pulmonary symptoms)
 oculoglandular (eye involvement and swollen cervical lymph
nodes)
 pharyngeal, ulceroglandular (cutaneous ulcer and swollen lymph
nodes),
 glandular (primarily swollen lymph nodes with no other localized
symptoms)

14. Treatment of Francisella tularensis:
 The organism is susceptible to aminoglycosides, and streptomycin is
the drug of choice.
 Gentamicin is a possible alternative and now considered as drug of
choice.
 Doxycycline and ciprofloxacin can be used to treat mild infections.
 Doxycycline and chloramphenicol also have been used, although
these two agents have been associated with a higher rate of relapse
after treatment.
 F. tularensis strains produce β-lactamase, which renders penicillins
cephalosporins ineffective.
 Fluoroquinolones appear promising for treatment of severe
tularemia.

15. Prevention and control of Francisella tularensis:
 Preventing bites from ticks, flies, as well as mosquitos.
 Refrain from drinking untreated water.
 Wearing protective clothing and using insect repellents reduce the
risk of exposure
 If working with cultures of F. tularensis in the laboratory, wearing
a gown, impermeable gloves, mask, and eye protection is must.
 Prompt removal of the tick can prevent infection.
 Persons who have a high risk of exposure (e.g., exposure to an
infectious aerosol) should be treated with prophylactic antibiotics.