Typing of sheep clinical isolates and identification of enterotoxigenic Clostridium perfringens strains by classical methods and by polymerase chain reaction (PCR).

A simple procedure was developed to identify toxitypes of Clostridium perfringens of different origins. Ninety strains of C. perfringens were identified by classical bacteriological methods, typing of the strains was done by a seroneutralisation test on mice. Production of enterotoxin was tested and all strains were analysed by PCR using gene of toxin alpha, gene of toxin E, gene of toxin beta and gene of enterotoxin. Simple amplification (amplifying one gene), and duplex and triplex amplification (amplifying two and three genes simultaneously) were performed. In the conditions of the experiment, the PCR method has proved efficacious. The specificity and sensitivity are excellent and superior to those of the classical methods. The prophylaxis of enterotoxaemia in animals is achieved by vaccination, the PCR technique can thus become a first-choice tool for the identification and typing of the C. perfringens strains which initiate these diseases. In turn, this would simplify the development of vaccines adapted to the epidemiological situation.

[Production of a vaccine against enterotoxemia from Clostridium perfringens strains isolated in the field]. / Contribution à la production d'un vaccin anti-entérotoxémie à partir de souches de Clostridium perfringens isolées sur le terrain.

We have isolated eight strains of C. perfringens from cases of enterotoxaemia. Five of these strains have revealed themselves toxic with respective types (type "A":2, type "C":2, type "D":1). In order to produce anti-enterotoxaemia vaccine, we have proceeded at the cultivation in fermenter of isolated strains and reference strains CWA 35, CWC and CWD AF. At the end of fermentation, we have evaluated the two following parameters: obtained biomass, and toxin titers. With the two classes of strains we reached an important biomass but toxins titers relatively weak comparatively to that which is usually required. It will be necessary then, to demonstrate the immunogen value of the produced vaccines by testing their efficacity.

[Optimization of culture conditions for the production of Salmonella typhi O and H antigenic suspensions]. / Optimisation des conditions de culture pour la production de suspensions antigéniques O et H de Salmonella typhi.

A Behring's production protocol of antigenic suspensions O and H of Salmonella typhi has been studied. The object of this study has been the Search of optimal conditions of cultivation and their exploitation on fermentor. A fermentation using the I.P.A culture medium has been realized to compare its results with that obtained using Behring's culture medium (B.C.M). The optimal cultivation conditions obtained are a waving rate of 400 tr/mn, a pH of 7.6 and an important air flow. Relating to nutritious constituents, the adequate glucose concentration is about 8g/1 and it seems better to replace meat extract by yeast extract. Comparatively to I.P.A culture medium, one of the most important advantage of Behring's culture medium modified reside in the conservation of the antigenicity of Salmonella typhi.