The genus Pasteurella is so designated in honor of Louis Pasteur, whose work on the “fowl cholera” VHS decimating flocks, led in 1880 to the first anti-bacterial vaccination.
I – CLASSIFICATION:
Recent taxonomic work based on DNA / DNA hybridization experiments lead one hand to assign as the Pasteurellastrains requiring factor V and secondly tend to depart from the genus Pasteurella species that were to be This included: P. haemolytica, P. pneumotropica, P. aerogenesand P. ureae.
The text below is devoted to the type species P. multocida.The characters of some related species that arePasteurella sensu and can be isolated in humans (P. dagmatis, P. canis) will be reported.
II – HABITAT AND EPIDEMIOLOGY:
Pasteurella are obligate parasites mucosal natural cavities of vertebrates. They are found with great frequency in the oral cavity and saliva of many species of animals: dogs, cats, horses, pigs, wild boar, etc.
Unable to survive long in the environment, Pasteurella are usually transmitted to humans by an animal.
III – PATHOGENICITY:
A – Human health:
1. Pasteurellosis of inoculation:
The most common, it is usually secondary to bite or griffade a dog or cat. All bites are not the starting point of pasteurellosis inoculation, but the inoculations at hand seem more serious.
After a brief incubation of 3 to 6 hours, very severe pain appear to inoculation points become very inflammatory.
The inflammation extends to neighborhood joints. Fever is inconstant. Satellite lymphadenopathy is rarely observed.Without proper treatment, the pain and inflammation subside spontaneously, but lameness persists.
Four to six weeks after inoculation, skin lesions are healed / but algo-dystrophic syndrome rebellious to any therapy persists and is a real disability. There is no lymphadenopathy satellite unlike the inoculation lymphoreticulosis.
2. Other forms of pasteurellosis:
They mostly occur in individuals who have an underlying disease. Septicemia, endocarditis and meningitis can be observed. P. multocida can be isolated from various pus: otitis, sinusitis, peritonitis, lymphadenitis. Of pleuropulmonary infections were reported, especially among pig farmers.
B – For the animal:
P. multocida is responsible for septicemia in poultry, of pneumonia in rabbits and ruminants. Atrophic rhinitis of swine where P. multocida is often associated with Bordetella bronchiseptica is the cause of significant economic losses. .
IV – PATHOPHYSIOLOGY:
From strains causing atrophic rhinitis, it was possible to identify a toxin with a dermonecrotic and osteolytic power.This localized in the cytoplasm peptide toxin is encoded by the A tox gene which has been cloned. Injected pigs, it reproduces the signs of atrophic rhinitis. This toxin was found in strains responsible for pleuropulmonary infections in humans.
V – CHARACTERS OF BACTERIOLOGICAL P. MULTOCIDA:
A – Body type:
These are Gram-negative coccobacilli usually with a coloring
bipolar. Among small bacterial body (L = 1-2 .mu.m; 1 = 0.3 to 0.4 (im)
long forms (L = 3-5 microns) are often observed. The chains are very rare.
A fresh, bacteria are immobile. The ink makes it possible to see a capsule whose thickness varies with the serotype.
B – Cropping characters:
The growth temperature is between 22 and 44 ° C with an optimum at 37 ° C. These are aero-anaerobic bacteria in deep agar with a small inhibition at the surface and a strengthening of growth in microaerophilic.
On rich media (serum agar, blood agar) after 24 hours of incubation at 37 ° C, the colonies are small (1-2 mm diameter) round, grayish, with dew drops. Sometimes, the importance of a given capsule mucoid. Broth, a homogeneous disorder is obtained within 24 hours.
There is no growth in the following media: MacConkey, Drigalski middle, middle Simmons citrate and yeast water.
C – biochemical characters:
– Catalase, nitrate reductase, ODC and indole are constantly positive.
– The following characters are negative: gelatinase, LDC, DHA, urease and H2S.
– All the strains were susceptible to vibriostatic 0/129 compound.
– The fermentation of glucose is always done without gas production. The following carbohydrates are regularly attacked mannitol, galactose, fructose, mannose, sucrose. By cons, are consistently negative: sorbose, rhamnose, inositol, adonitol.
The study of fermentation of sorbitol and dulcitol allows for P. multocida recognize three subspecies listed below:
D – antigenic characters:
Polysaccharides constituting the capsule allow, depending on their composition, typically distinguish 4 capsular types: A, B, D, and E. A fifth type capsular F, described for strains isolated from turkey.
The wall lipopolysaccharide, with the characters of the endotoxins of Gram-negative bacilli, used to classify strains into 12 serotypes.
Capsular and somatic serotyping therefore exists, but it is not used in current practice due to the complexity of this determination.
E – Experimental pathogenicity:
Mice inoculated intraperitoneally quickly died of septicemia. This ability to kill the mouse can be lost by strains that lack of capsule.
VI – OTHER SPECIES OF THE GENUS PASTEURELLA:
The differential characters of P. P. multocida with canis and P. dagmatis are shown in Table I. These two species are pathogenic for man neighbor to that of P. multocida.
The other four species listed in the table with “P” are not Pasteurella sensu and are awaiting a more precise taxonomic position.
“P. “Haemolytica is often pathogenic to livestock: cattle, pigs, poultry. As “P. “Pneumotropica, it grows on MacConkey agar.
VII – LABORATORY DIAGNOSIS OF INFECTION P. MULTOCIDA:
A – Isolation of P. multocida:
It is most often collected from serous fluids deep into injury bites. Conventionally there is a fast self-sterilization lesions; However, it is often possible to find P. multocida in bites after several days.
In other pathological products isolation of P. multocida is often fortuitous (bronchial secretions). Selective medium containing 2 mg / 1 of amikacin and 4 mg / 1 vancomycin can be useful for multi-microbial samples.
B – Indirect diagnosis:
Search serum antibody has no practical interest.
Indirect diagnosis useful in chronic forms where there are more bacteria in lesions, is done by the intradermal pasteurelline Reilly.
An allergic reaction of delayed hypersensitivity appear 10-20 days after inoculation of Pasteurella multocida. The antigen used or pasteurelline is a filtrate of a culture broth of P. multocida. Intradermal injection is carried out with 0.5 ml of pasteurelline.
The reading should be relatively early because the reaction starts at the 6th hour, up to 12 hours and decreases in the 24th hour. The local reaction (lupus cupboard) must be at least 3 cm to be meaningful. It is often accompanied by a focal reaction: sensitivity of the inoculation area, joint pain, thermal buoyancy.
The delayed hypersensitivity to pasteurelline persists for years. It is always clear in chronic algodystrophiques forms.It can be negative if the patient is receiving corticosteroids or other anti-inflammatory drugs.
VIII – TREATMENT OF pasteurellosis:
A – Antibiotics:
Strains of P. multocida isolated from humans are generally sensitive to tetracyclines, penicillin G and ampicillin, which are the antibiotics of choice for pasteurellosis inoculation. The bovine strains are less sensitive and can withstand penicillin producing a ROB-1 beta-lactamase. The strains isolated in humans that produce beta-lactamase are still rare.
Aminoglycosides are not very active and should not be used alone to treat an infection with P. multocida.
B – Antigénothérapie:
In chronic forms algodystrophiques, antibiotics are ineffective.
An improvement can be achieved by 4 intradermal injections of 5 or pasteurelline separated by a week each.