ABSTRACT
An experimental technology for the production of live freeze-dried vaccines prepared from attenuated Shigella flexneri 2a and Shigella sonnei I strains was developed. It is based on the cultivation of bacterial strains in a fermentor under conditions which ensure high yields. The strains grow in S-form, their antigenic structure is preserved and they remain non-virulent. The attenuating markers are stable. The freeze-dried vaccines retain good immunogenicity when applied intra-intestinally to rats.
Subject(s)
Bacterial Vaccines , Dysentery, Bacillary/immunology , Shigella flexneri/immunology , Shigella sonnei/immunology , Administration, Oral , Animals , Antibodies, Bacterial/immunology , Bacterial Vaccines/administration & dosage , Bacterial Vaccines/immunology , Freeze Drying , Guinea Pigs , Rats , Shigella flexneri/growth & development , Shigella sonnei/growth & development , Vaccines, Attenuated/administration & dosage , Vaccines, Attenuated/immunologyABSTRACT
The method for the cultivation of S. flexneri attenuated strain 2a 77 ade- rifr in a fermenter with the use of casein fermentative broth containing 200-250 mg% of amino nitrogen has been developed. No changes in the properties of the initial strain have been found after its cultivation in a fermenter or after the lyophilization of the cultures grown in a fermenter. After cultivation in casein fermentative broth with 100 mg% of amino nitrogen the presence of S-R dissociation has been established, the S colonies having the properties of the initial strain. The reversion of the R colonies to prototrophism in adenine and differences in the level of their resistance to rifampicin are observed. The study of the plasmid profile of the initial strain and its ade+ revertants has revealed the disappearance of plasmids with a molecular weight of 140 MD in these revertants. All clones under study (ade+ and ade-) show negative results in the keratoconjunctival test. The conditions of cultivation and the causes of reversion are discussed.
Subject(s)
Shigella flexneri/growth & development , Fermentation , Freeze Drying , PlasmidsABSTRACT
A method was developed for cultivation of the strain Shigella flexneri 2a 77 with two attenuated markers. It ensures the preservation of the initial properties of the strain. The regimen for control of dissolved oxygen level was optimized. It was established that yeast extract is a necessary component of the nutritive medium used. The role of the phase and quantity of the inoculum for growth of the bacterial population has been clarified. Fresh fermenter culture, applied in rats, shows a high immunogenic activity. After lyophilization, the cultures retain 50-70% of the immunogenic activity of the non-lyophilized cultures. The method makes preconditions for the production of a live attenuated dysentery vaccine for oral administration.
