[Effect of certain factors on Vibrio cholerae multiplication in fermenter]. / Vliianie nekotorykh faktorov na razmnzhenie kholernykh vibrionov v fermentere.

The influence of the level of dissolved oxygen, as well as the phase of growth and the amount of inoculum introduced, on the growth of bacterial population in the process of the cultivation of cholera vibrios in the fermenter "Novopalias" has been studied. The results of this study indicate that the cultivation of cholera vibrios with the level of dissolved oxygen constituting 50% of the maximum air saturation of the broth ensures a better yield of the biomass than cultivation with the level of dissolved oxygen equal to 10% and 30%. The introduction of inoculum in an amount of 1 : 20 (inoculum/medium) does not ensure a better yield of the biomass than an amount of 1 : 100 introduced at the phase of stationary growth. Cultivation at 50% pO2 and the introduction of inoculum in an amount of 1 : 100 at the phase of stationary growth have demonstrated some technical advantages in comparison with the introduction of inoculum at the phase of exponential growth, which allows one to use this technique for the production of cholera vaccine.

[2-cycle culture of Vibrio cholerae in a fermenter]. / Dvukhtsiklicheskoe kul'tivirovanie kholernykh vibrionov v fermentere.

The method for the two-cycle cultivation of V. cholerae, reference strains Inaba and Ogawa, in a fermenter has been developed. In the first and second cultivation cycles no difference in the yield of the biomass and in the ultrastructure of the vibrios has been established. In the second cycle a decrease in the minimum time of generation has been observed. The vaccines obtained in the first and second cultivation cycles have not been found to differ in their antigenic and immunogenic activity. The vaccines meet the WHO requirements.

[Cholera vibrio culture in a fermenter with automatic control of a number of parameters]. / Kultivirovanie kholernykh vibrionov v fermentere s avtomaticheskim kontrolem riada parametrov.

The cultivation of V. cholerae was carried out in casein broth in a fermenter. 2 kinds of cultivation conditions were compared. The results thus obtained indicate that the cultivation of V. cholerae under the conditions of the controlled level of dissolved oxygen (pO2--50%) ensures the optimum conditions for proliferation and the high yield of biomass; it also allows obtaining vaccine whose immunogenic properties are not inferior to those of the WHO reference vaccine.

[Standardization of cholera vaccine and preparation of a national reference standard]. / Standartizatsiia kholernoi vaktsiny, izgotovlenie natsional'nogo referens-preparata.

The antigenic potency of the proposed national reference preparations in comparison with that of the corresponding international reference preparations was studied by means of the active protection test in mice. The antigenic potency of the proposed national reference preparations for Inaba and Ogawa was found to be the same or even greater than the antigenic potency of the international reference preparations for cholera vaccine. A high level of antigenic activity was observed during comparison of a production lot of cholera divaccine with the international reference preparation and the national reference preparation in parallel tests. The proposed national reference preparations for Inaba and Ogawa may be used for evaluating the antigenic potency of the lot of cholera vaccine produced in Bulgaria as the standard preparation.

[Experience of the People's Republic of Bulgaria in controlling diphtheria, tetanus and whooping cough]. / Opyt Narodnoi Respubliki Bolgarii v bor'be s difteriei, stolbniakom i kokliushem.

The analysis of the morbidity and mortality rates in diphtheria, tetanus and pertussis in Bulgaria after the introduction of the compulsory mass immunization of children with combined DPT vaccine is presented. These data indicate that morbidity in diphtheria, tetanus and pertussis has sharply decreased. Favorable results with respect to these three diseases are the consequence of the complete coverage of the child population by immunization with the vaccine whose quality has been steadily improving for the last 20 years. A higher purity of toxoids has been achieved, and at present it exceeds the latest WHO requirements. Pertussis vaccine is produced with the use of strains whose serological characteristics correspond to those of the pertussis strains circulating in the country. The study of the reactogenicity of DPT vaccine, carried out over the period of 20 years, has shown that the vaccine has low reactogenicity.

[Improvement in the laboratory methods of assessing the safety of the of the pertussis component of DPT vaccine adsorbed]. / Usovershenstvovanie laboratornykh metodov otsenki bezvrednosti kokliushnogo komponenta AKDS-vaktsiny.

The mouse paw edema test and the tests for the determination of leukocytosis-stimulating and histamine-sensitizing activity are reproducible if standard samples are used and the properties under test are evaluated with reference to the characteristics of standard samples. The standard character of the weight gain test on mice is also enhanced if all conditions of the test are standardized. The most accurate information on the toxicity of the pertussis component of adsorbed DPT vaccine can be obtained if a single human dose (0.5 ml) is injected to mice and the toxicity of the vaccine is estimated from the weight gain registered in the test mice and the control animals. The use of standard samples in each test makes it possible to observe the conditions for controlling the toxicity of the tested preparations.

[The standardization of the methods for assessing the immunogenic activity of all of the components of an adsorbed DTP vaccine]. / K voprosu o standartizatsii metodov otsenki immunolennoi aktivnosti vsekh komponentov AKDS-vaktsiny.

The reproducibility of laboratory methods, recommended by WHO and used by manufacturing and control institutions of most countries for the evaluation of the immunogenic potency of the pertussis, diphtheria and tetanus components of adsorbed DPT vaccine in the process of its production, was studied. This immunogenic potency was experimentally studied in comparison with the immunogenic potency of national standard samples from Bulgaria, Czechoslovakia, Hungary, Poland and Russia. The results of this study indicated that the coded commercial lots of adsorbed DPT vaccine corresponded to WHO requirements with respect to the immunogenic potency of all their components. At the same time, according to data provided by different laboratories, the indices of their immunogenic potency varied within rather wide limits. Taking into account the necessity of dosing all components of adsorbed DPT vaccine by immunizing (protective) units, the reliability of the recommended control methods should be enhanced by the maximum standardization of all testing conditions and the organization of periodic workshops on the basis of the leading WHO laboratory with a view to improving the qualification of specialists carrying out the quality control of commercial lots of adsorbed DPT vaccine.