Francisella tularensis: morphology, tradition traits, pathogenesis , prognosis and therapy

Francisella tularensis outcomes tularaemia in man and sure small mammals, resembling rabbits, hares, beavers and several other rodent species.
Tularaemia was initially described in Tulare county, California.
It may be transmitted by direct contact, by biting flies, mosquitoes and ticks, by contaminated water or meat or aerosols.
Francisella tularensis can also be know as Pasteurella tularensis or Brucella tulerensis)

**Morphology of Francisella tularensis:**

It’s a very small, nonmotile, nonsporing, capsulate, gram-negative coccobacillus, about 0.3 to 0.7 μm × 0.2 μm in dimension.
In tradition it tends to be pleomorphic to and bigger, even filamentous, types are current.
It stains poorly with methylene blue however dilute carbol fuchsin (10%) produces attribute bipolar staining.

F. tularensis is strictly cardio.
It won’t develop on bizarre nutrient media however grows nicely on blood agar containing 2.5 % glucose and 0.1 % cysteine hydrochloride.
Minute droplet-like colonies develop in 72 hours.

Beneath appropriate circumstances acid is shaped from glucose and maltose. Indole and urease checks are adverse.
Two biovars are acknowledged. Strains of F. tularensis have been subdivided into biotypes based mostly on their virulence and epidemiological behaviour.
Extremely virulent strains are discovered solely in N. America, whereas strains of low virulence are seen in Europe and Asia additionally.

The an infection, which is a typical zoonosis, is principally unfold by bugs or ticks amongst lagomorphs and rodents.
It’s transmitted to man by way of dealing with of contaminated animals, e.g. rabbits or hares tick, mosquito or fly bites, inhalation of contaminated mud, ingestion of contaminated water or meat.
Laboratory staff are at larger danger whereas dealing with contaminated laboratory animals or cultures of the organism.
Man to man transmission of an infection apparently doesn’t happen.
In human beings, tularemia might current as an area ulceration with lymphadenitis, a typhoid like fever with glandular enlargement or an influenza like respiratory an infection.
The severity of illness is far larger with kind A strains and case fatality charges might exceed 5 %.
Illness attributable to kind B strains is far much less extreme, with very low mortality.

F. tularensis is extraordinarily harmful to deal with within the laboratory and Class 3 containment is required for all manipulations and animal work.
Prognosis could also be made by tradition or by inoculation into guinea pigs or mice. A PCR has been described, however shouldn’t be broadly obtainable.
Serology is probably to be constructive after 3 weeks.
Rising titres of agglutinins to F. tularensis or particular person titres of 160 are diagnostic.
Serum from instances of F. tularensis might cross-react with brucellosis and vice versa, normally to comparatively low titre.
An intradermal delayed hypersensitivity check has been used prior to now however the antigen shouldn’t be available.

Streptomycin or gentamicin are the antibiotics of alternative in tularaemia and are normally healing.

Prophylaxis:

A vaccine based mostly on the live-attenuated LVS pressure confers some safety.
It may be administered by scarification to individuals who’re topic to excessive danger of an infection.
F. tularensis has been developed as a organic warfare agent and has potential software in bioterrorism.