The Bactérie Vibrio cholerae (choleraic vibrio or bacillus comma in French) is a bacterium negative Gram, in the shape of bent stick, responsible for the Choléra at the Homme, a epidemic Maladie Contagieuse.

History

During centuries, the disease remains unknown in the Europe, being propagated especially in Asia and Africa. The first mention of this disease in Europe is made in 1503 by a Portuguese officer ghost of the Indies, telling a disease there having made: 20000 dead. It appeared thereafter in Europe and was the object of a crowd of interpretations and theories on behalf of the doctors. It is at the time of the epidemic of 1854, with London, that the comprehension of the disease knows an major advance. One realized that the disease struck near certain wells, suggesting a contamination by the Eau. But this assumption was not immediately allowed at the time.

Vibrio cholerae for the first time was insulated like the person in charge of the cholera by the Italian anatomist Filippo Pacini in 1854. But its discovery will be ignored because of the prédominence of the Théorie of miasma, charging the responsibility for the cholera (and other diseases which one did not know the origin) to a bad quality of the air. Thirty years later, Robert Koch, which is not with the current of the results of Pacini, publishes the result of its work and the means of fighting Vibrio cholerae.

In 1965, the bacterium is re-elected in Vibrio cholerae (Pacini, 1854) in homage to Filippo Pacini.

Ecology

Habitat

The bacterium Vibrio cholerae lives in water and has a great capacity of environmental survival. It tolerates salinity very well but really does not find itself in Mer but rather in the Estuaire S, the Rivière S and the ground water and all the sources of water contaminated by human dejections.

It seems that certain shellfish (in particular the Crevette S) play a part of vector thanks to receivers located on their dorsal carapaces.

Pathogenic capacity

The disease with for only tank, seems T is exclusively human the human being. It touches the zones over-populated and underprivileged because the hydrous absence of hygiene and the denutrition support the contraction of the cholera. It touches the old extremes of the life in particular the children.

Since 1992, it did not have there a human endogenous case in France. It is on this same date that one discovers a new stock which is an adaptation of the preceding historical stock which was called Vibrio cholerae O1 , This new stock named Vibrio cholerae O139 seems to have acquired a capacity to disseminate infections which will make of it the source of hypothetical a 8th Pandémie, in particular in India and with the Bangladesh.

The Vibrio is very contagious because it contaminates the saddles massively, the choleraic Diarrhée is very important in volume, with water losses which can reach 15 Liters per days. Incubation is in general rapid for the subjects in a state of malnutrition: The gastric absence of acidity supports the infection. According to the size of the Inoculum the beginnings of the symptoms occur in a few hours at a few days after the Contamination.

The diarrhea is without fever, forces, slightly aqueous turbide: it is known as in " water of riz" who with terms causes severe a Déshydratation and major electrolytic disorders (escape of Chlore and an inhibition of the absorption of the Sodium) which will be the cause of death by cardiovascular Collapsus, this one occurring depending on the state of the patients, in 25 to 50% of the cases; if all the care necessary is applied (what is seldom the case in the countries touched hard), lethality passes in lower part of 1%.

The bacterium does not enter the organization and does nothing but there forward, it has a weak invasive capacity. It owes all its pathogenicity with its toxic capacity. Extremely mobile, like the majority of the vibrios, it moves very quickly in water and multiplies there very quickly. It are euryhaline and resist well the variations of '' p '' H (in particular alkaline).

They have a particular affinity with the Mucus which recovers the barrier entérocytaire, it will penetrate it and thanks to the presence of complexes pili - TCP (comparable to Adhésine) at the polar end of the bacterial body, close to the Flagelle, will cling to the cells Intestin. These same pili is also the receivers of Bactériophage S CTX of which the Génome encode powerful a Toxine which is the choleraic toxin (see the following chapter).

The toxin is made up of two groups of structures, the five structures B which will be used for fixing of toxin on the membranes of the entérocytes by setting on a membrane ganglioside GM1 , and single structure has which activates a Enzyme: the Adénylate cyclase which catalyzes the Adénosine triphosphate in cyclic Adénosine monophosphate, the EC-last being responsible, at the entérocytes, of the chlorine and water leakage in the intestinal light and of the blocking of sodium.

Vibrio cholerae and bacteriophage CTX

Vibrio cholerae is not in the pathogenic beginning, it is the Bactériophage CTX which returns it thus. Researchers of the Institut Pasteur in France published in the review Molecular Cell an article explaining how CTX made to insert its DNA in that of Vibrio cholerae and thus to make it pathogenic.

The characteristic of CTX is that it manages to introduce its genetic material into the DNA of Vibrio cholerae whereas their two genetic codes are incompatible. Indeed, Vibrio cholerae has a circular DNA doubles bit whereas that of CTX is with simple bit. It is integrated thanks to the Recombinase S XerCD.

Reference

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