[The evolution of meningococcal infection in Mongolia]. / Evoliutsiia meningokokkovoi infektsii v Mongolii.

On the basis of the generalization and analysis of the results of bacteriological and immunological investigations the epidemic process of meningococcal infection (MI) in Mongolia was found to undergo definite changes during the last 20 years. Group A meningococci prevailing in the etiology of MI were replaced by strains belonging to group B affecting mainly young children (aged up to 3 years). MI morbidity rate caused by group B meningococci was found to be higher in Mongolia than in other countries of the world. These data substantiate the necessity of using more effective remedies for the control of this infection and, in particular, specific immunization with vaccines against group B meningococci; profound study of the properties of the circulating meningococcal strains is to be carried out.

[The determination of antimeningococcal antibodies in the saliva of healthy people]. / Opredelenie protivomeningokokkovykh antitel v sliune zdorovykh liudei.

The determination of antibodies to the group-specific polysaccharide of group A meningococci (PS-A) in the saliva of 162 healthy persons at different seasons of the year revealed that antimeningococcal antibodies could be detected in all examines. The range of concentrations of antibodies to PS-A varied between 0.1 and 33.0 U/ml. The comparison of antibody content with the levels of morbidity in meningococcal infection and carriership made it possible to determine two threshold levels of antibody concentration: 9.0 U/ml and 18.0 U/ml.

[The drug sensitivity of meningococci and the characteristics of its determination]. / Lekarstvennaia chuvstvitel'nost' meningokokkov i osobennosti ee opredeleniia.

The results obtained in the study of antibiotic and sulfamide sensitivity of 197 Neisseria meningitidis strains of groups A, B and C, isolated from the spinal fluid and blood of patients with meningococcal infection hospitalized in the 2nd Clinico-Infectious Hospital, Moscow, in 1984-1989 and studied with the use of the disc diffusion method and the method of serial dilutions of antibiotics in solid culture media, are presented. As revealed in this study, N. meningitidis strains retained their high sensitivity to penicillin and ampicillin (MIC50 = 0.016 and 0.032 micrograms/ml respectively). Sensitivity to tetracycline decreased (MIC50 = 0.5 micrograms/ml) and to rifampicin increased (MIC50 = 0.063 micrograms/ml). 48.5% of strains were resistant to streptomycin. In recent years the proportion of N. meningitidis, resistant to sulfanilamide preparations, significantly decreased and MIC50 was equal to 2.5 micrograms/ml in comparison with 5-10 micrograms/ml in the preceding period. The results of testing sensitivity to antibiotics by both methods coincided. Still the disc diffusion method can be used in epidemiological surveillance on meningococcal infection, while for more exact differentiation of N. meningitidis strains the use of the method of serial dilutions is necessary.

[The characteristics of suppurative meningitis morbidity caused by Streptococcus pneumoniae and Haemophilus influenza type B]. / Osobennosti zabolevaemosti gnoinymi meningitami, vyzvannymi Streptococcus pneumoniae i Haemophilus influenzae tipa B.

Of the 1,018 patients with purulent bacterial meningitis, hospitalized at the 2nd Clinical Infectious Hospital in Moscow during the period of 1980-1987, the diagnosis was confirmed in 54.7%; of these, meningitis of pneumococcal etiology was established in 44.8% and meningitis caused by H. influenzae, type b, in 23.8% of the patients. In meningitis of pneumococcal etiology high risk groups included mainly adults, especially those over 50 years, and children under 3 years of age. In meningitis of H. influenzae etiology high risk groups included mainly young children under 2 years of age. Meningitis of pneumococcal etiology was characterized by considerable death rate (on the average, 20%), while in meningitis of H. influenzae etiology death rate was 3 times lower. Pneumococci of serotypes 1, 3, 6, and 19 were found to be of the highest etiological importance for adults and pneumococci of serotypes 19, 6, 12, and 1, for children. In recent years greater etiological role of serotype 42 in adults was noted. The study of the spread of meningitides of different etiology is a high-priority task for this country.

[Immunological factors in the evolution of the epidemic process in meningococcal infection]. / Immunologicheskii faktor v évoliutsii épidemicheskogo protsessa pri meningokokkovoi infektsii.

The results obtained in 1987 in the study of the immunostructure of the population of Yaroslavl with respect to meningococcal polysaccharides, groups, A, B, C, and lipopolysaccharide are presented in comparison with earlier results obtained in 1976. The regulating role of the immunological factor in the evolution of the epidemic process of meningococcal infection has been confirmed. The level of antibodies to meningococcal polysaccharides, groups A and B, has been found to reflect the intensity of the circulation of the infective agent among the population. The comparison of the results of investigations carried out in 1976 and 1987 has revealed the essential role of the lipopolysaccharide antigen in the formation of the postinfection immunity of the population to meningococcal infection, irrespective of the group of the infective agent.

[Epidemiological surveillance of meningococcal infection and the prediction of the development of an epidemic process]. / Epidemiologicheskii nadzor za meningokokkovoi infektsii i prognozirovanie razvitiia épidemicheskogo protsessa.

The signs necessary for the prognostication of the development of the epidemic process have been formulated on the basis of the epidemiological analysis of materials obtained in the process of trials of the system for the surveillance of meningococcal infection with the use of previously established characteristics. The data on the prevalence of meningococcal infection among different age groups and on the seasonal distribution of the infection as well as on the serogroups of meningococci isolated from patients, have been shown to be of importance for prognostication.

[Antigenic affinity of meningococci and human A- and B-group erythrocytes]. / Antigennoe rodstvo meningokokkov i éritrotsitov cheloveka gruppy A i B.

The use of the modified method of isohemagglutinin adsorption by microbial antigens in experiments with the causative agent of meningococcal infection has led, for the first time, to the detection of meningococcal antigens affined to the antigens of human erythrocytes, groups A and B. The antigenic affinity of group A erythrocytes and meningococci has proved to be more pronounced in meningococcal strains isolated from the spinal fluid of patients than in cultures obtained from the nasopharynx of healthy persons. The detection of the affinity of these antigens makes it possible to explain the mechanism of differences in the susceptibility of persons with different blood groups to meningococcal infection by "antigenic mimicry".

[Etiological diagnosis of suppurative bacterial meningitis today]. / Etiologicheskaia diagnostika gnoinykh bakterial'nykh meningitov v sovremennykh usloviiakh.

As the result of laboratory examination of 2165 patients with virulent bacterial meningitides, including cases of meningococcal infection, the etiological diagnosis was confirmed in 1407 patients (65.0%), the number of cases confirmed by the laboratory examination being significantly greater among adults than among children: 67.5 +/- 1.37% and 63.1 +/- 1.53%, respectively, (t = 2.1). Meningococcal infection was confirmed in 1111 (70.6%) out of 1572 patients under examination. Of the patients with purulent meningitides, pneumococcal etiology was determined in 27.4%, type b of Haemophilus influenzae in 13.5%, other infective agents in 10.0%. The comparison of the results obtained in the examination, carried out by different methods, of 946 children and 770 adults with meningococcal infection revealed a considerable difference in the number of positive results yielded by the bacteriological method and countercurrent immunoelectrophoresis (CIE). Among adults meningococci were isolated twice as frequently (41.1 +/- 2.5% - 19.4 +/- 1.6%), and the results yielded by CIE were predominantly positive (55.1 +/- 2.5% and 40.1 +/- 2.5%). CIE and the immunoenzyme assay were shown to have advantages in the diagnosis of the disease. Under the conditions of intensive antibiotic therapy the methods based on the detection of specific antigens in body fluids can greatly assist in diagnosis.

[Etiology of suppurative bacterial meningitis]. / Etiologiia gnoinykh bakterial'nykh meningitov.

The results of the laboratory examination of 2034 patients with meningococcal infection and purulent meningitides, hospitalized during the period of June 1980 to October 1983, revealed that three main etiological agents were responsible for these diseases: meningococci, pneumococci and Haemophilus influenzae. The susceptibility of the patients to different etiological agents was found to depend on their age. Children aged up to 3 years constituted 75% of the patients with meningitis caused by H. influenzae; 50% of the patients with meningococcal infection were children aged up to 5 years; pneumococcal meningitis occurred more frequently in adults. Serogroup A meningococci were found to prevail in patients with meningococcal infection. Besides, in children serogroup C meningococci could be isolated in 24% of cases. Since 1983 the cases of the isolation of strains belonging to serogroup B increased in number. Among the pneumococci responsible for the disease serotypes 1, 19, 6 and in children serotype 12 occurred most frequently.

[Immunoepidemiological characteristics of the duration of a meningococcal carrier state]. / Immunoépidemiologicheskaia khrakteristika dlitel'nosti meningokokkovogo nositel'stva.

The duration of meningococcal carriership in children and adults in the foci of infection and outside such foci and the immunological characteristics relating to group-specific meningococcal antigens A, C, X, Y and Z at different periods after the detection of the infective agent in the nasopharynx have been studied. Carrier state has been shown to last, on the average, 11 days. The duration of the release of meningococci from the nasopharynx has proved to be influenced by the epidemic situation in a given group. Differences in the time course of the immunological reorganization of the body in response to antigenic challenge in prolonged and short-term carrier state have been detected. These data suggest that rapid immune response to meningococcal antigens in the process of short-term carrier state is probably one of the factors preventing the prolonged colonization of the nasopharynx by the infective agent.

[Criteria of the epidemiological surveillance of meningococcal infection]. / K voprosu o kriteriiakh épidemiologicheskogo nadzora za meningokokkovoi infektsiei.

The results of studies carried out with the use of the unified, specially developed methods in eight regions of the USSR are generalized. Basing on the analysis of the results, the leading role of serogroup A meningococci in the rise of morbidity is emphasized, the relation of the morbidity level to the serogroup composition of meningococci circulating among healthy population is revealed, the necessity of carrying out selective bacteriological surveys with a view to establish the serogroups of meningococci circulating among the population is shown. The expedient criteria to be used in the system of epidemiological surveillance of meningococcal infection are presented.

[Immunoepidemiological study of the meningococcal carrier state in groups of children and adolescents]. / Immunoépidemiologicheskoe izuchenie meningokokkovogo nositel'stva v kollektivakh detei i podrostkov.

Immunoepidemiological study in groups of children of different ages was carried out. The study comprised the monthly bacteriological examination of the members of these groups and selective determination of the presence of specific meningococcal A- and C-antibodies, IgA, IgM and IgG in the blood serum, as well as the lysozyme activity of the saliva. The results thus obtained indicated that during the whole year two rises in the level of meningococcal carriership, in autumn and in spring, were registered, while the cases of meningococcal diseases were absent. The first rise was due to the influence of the conditions under which the groups had been formed, as well as to some decrease in specific immunity characteristics and nonspecific protective factors; the second rise occurred simultaneously with a considerable decrease in the content of specific meningococcal A- and O-antibodies.

[Evaluation of the role of specific antimeningococcal antibodies in the spread of meningococcal carrier states in collectives]. / Otsenka roli spetsificheskikh antimeningokokkovykh antitel v rasprostranenii meningokokkovogo nositel'stva v kollektivakh.

The results of serological, bacteriological and epidemiological studies carried out in populations with different epidemic pattern of meningococcal infection are presented. A-group specific antibody was found to have the leading role in the intensity of the spread of meningococcal infection in the populations. The presence of antibody to this antigen in 16.7% of serum samples inhibited dissemination of meningococci in the populations. Simultaneously with an increase in the herd immunity level to 34.8% the attenuation of the active meningococcal dissemination cycle was observed. Meningococci isolated in the populations with different epidemic patterns of meningococcal infection were shown to have different ecological properties.

[Evaluation of the sanative action of rifampicin on the meningococcal carrier state]. / Otsenka saniruiushchego deistviia rifampitsina na nositel'stvo meningokokkov.

The results of the epidemiological control experiment on the efficacy of rifampicin in sanation of meningococci carriers are presented. The preliminary study of rifampicin sensitivity of 41 freshly isolated nasopharyngeal meningococcal strains showed that the MIC of the drug for 63 per cent of the isolates was 0.04--0.1 gamma/ml. Sanation was performed for 2 days; 1.2 g of the drug was used during the treatment course. The results of examination of 91 meningococci carriers showed that 4 days after the sanation the specific weight of the persons isolating no meningococci was reliably higher in the experimental group than that in the control group. The coefficient of rifampicin efficiency was 70.8 per cent. 10 days after sanation the difference in the level of the carriers isolating no meningococci in the experimental and the control groups was statistically insignificant. Therefore, the carriers treated with the drug received temporary protection from the causative agent at an average for 1 week. Later on they could become carriers again. As a result of sanation no changes in the meningococcal sensitivity to rifampicin was observed.