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The possibility of using paper indicator discs with glucose, saccharose, lactose and urea, manufactured at the Gorky Research Institute of Epidemiology and Microbiology, has been studied and the methods for the preparation of indicator discs with fructose, maltose, starch and sodium phenolphthalein-phosphate for the biochemical identification of C. diphtheriae, N. meningitidis and staphylococci have been proposed. The study of 395 C. diphtheriae strains, 98 N. meningitidis strains and 328 staphylococcal strains has shown that paper indicator systems are highly sensitive and specific, which makes it possible to recommend their introduction in laboratory practice for the rapid identification of the above-mentioned organisms.

Filter paper discs have been used in the enzyme immunoassay (EIA) as solid phase instead of polystyrene plates. The use of paper discs has made it possible to achieve a multiple increase in the sensitivity of sandwich EIA, thus permitting the detection of Yersinia pestis capsular antigen at a concentration of 0.4 ng/ml. Paper discs can be used not only for the sorption of antigen and antibodies, but also for the affinity purification of preparations.

A paper indicator system has been developed in the USSR for the accelerated identification of vibrios and proposed for the identification of enterobacteria. This system consists of paper discs or strips impregnated with definite substrates (carbohydrates, polyatomic alcohols, amino acids, etc.) in combination with an indicator and stabilized with the polymer coating. Two kits for the identification of enterobacteria to the level of the genus (kit A for 9 tests) and to the level of the species (kit B for 25 tests) are presented.

The method for the determination of the toxigenicity of C. diphtheriae by means of discs impregnated with diphtheria antitoxin is proposed. The discs can be prepared long before use and stored for a year. The determination of toxigenicity with these discs is not inferior in its sensitivity to the routine procedure of the immunoprecipitation test. The disc method decreases the consumption of unavailable diphtheria antitoxin by 10 times, that of culture media by 2-2.5 times: besides, it is less labor consuming.

A total of 5082 cultures belonging to the family Vibrionaceae and 100 strains of enterobacteria were identified by means of the paper indicator systems manufactured by the Gorky Research Institute of Epidemiology and Microbiology and with the use of the classical method. The results thus obtained indicate that these systems proved to be sufficiently sensitive and specific, which allows one to recommend them for wide introduction into laboratory practice.