[Multilocus sequencing of Corynebacterium diphtheriae strains isolated in Russia in 2002 - 2012].

AIM: Characterization of contemporary C. diphtheriae strains isolated in Russia by using multilocus DNA sequencing (MLST). MATERIALS AND METHODS: 28 toxigenic C. diphtheriae strains isolated in Russia in 2002-2012 and sent to diphtheria and pertussis reference center of Gabrichevsky Research Institute of Epidemiology and Microbiology were studied. C. diphtheriae strain genotyping was performed by using MLST based on atpA, dnaE, dnaK, fusA, leuA, odhA and rpoB gene fragments. Identification of alleles and ST was carried out according to EMBL/GenBank and PubMLST, eBurst approach was used for cluster analysis. RESULTS: By using MLST contemporary toxigenic C. diphtheriae strains isolated in Russia in 2002 - 2012 were characterized. 8 genotypes (ST41, ST5, ST8, ST28, ST25, ST44, ST-new1 and ST-new2) were identified, 3 among them were dominating--ST8, ST28 and ST-new1. Most of the toxigenic strains belong to biovar gravis and ST8. Among biovar mitis strains a higher heterogeneity by ST membership was noted, but with prevalence of ST28 strains. CONCLUSION: Use of MLST allowed to characterize contemporary circulating population of toxigenic C. diphtheriae strains isolated in Russia and showed perspective of application of this method for characterization of diphtheria causative agent population and detection of epidemically significant strains, as well as juxtaposing of them with genetic structure of foreign strains.

[Genotypic differences between Corynebacterium diphtheriae biovar gravis and mitis strains].

AIM: Study structure ofa genetic determinant of amylase activity (amygene) in Corynebacterium diphtheriae biovar gravis and mitis strains. MATERIALS AND METHODS: 87 C. diphtheriae strains (31 gravis biovar strains and 56 mitis biovar strains) as well as C. diphtheriae PW8 strain were analyzed to detect structural features of C. diphtheriae strains of various biovars. 10 pairs of primers were used in PCR that flank mutually overlapping regions within DIP0357 locus as well as additional primers that flank DIP0353-DIP0354, DIP0357 and DIP0358 loci. RESULTS: All the C. diphtheriae biovar gravis strains were established to contain a full-size DIP0357 locus (amy gene) whereas in all the mitis biovar strains this genome fragment is absent. All the studied C. diphtheriae biovar gravis strains do not have significant changes within DIP0354-DIP0357 loci (amy gene) whereas in genome of 57 studied C. diphtheriae biovar mitis strains the major part of this fragment including the complete nucleotide sequence of amy gene is absent. CONCLUSION: C. diphtheriae biovar gravis strains have a genetically determined ability to produce amylase that can be viewed as an additional pathogenicity factor giving microorganisms wider capabilities to colonize the mucous membrane of oropharynx.

[The quality control of nutrient medium in laboratory bacteriologic diagnostics of diphtheria].

The article deals with the results of studying the growth characteristics of nine nutrient mediums for primary plating of pathologic material. It is demonstrated that for successful and proper functioning of bacteriologic laboratory providing bacterial analysis for diphtheria the permanent quality control is needed to monitor the nutrient mediums for primary plating. The quality control is applied to evaluate the growth characteristics on such criteria as germination of isolated culture, intensity of its growth in 24 and 48 hours, optimal size of colonies characterized by their cultural characteristics, inhibiting activity concerning concurrent microflora.

[Characteristics of Bordetelia pertussis strains isolated from pertussis patients in Moscow by using multilocus sequencing].

AIM: Genotyping of B. pertussis strains isolated from pertussis patients in Moscow. MATERIALS AND METHODS: 53 strains of B. pertussis isolated from pertussis patients in Moscow in 2007 - 2010 as well as 3 vaccine strains currently used in Russia for the production of DTP vaccine were studied by multilocus sequencing (MLST) based on allele combinations of ptxA, ptxC and tcfA genes. RESULTS: A genetic characteristic of B. pertussis strains isolated from pertussis patients in Moscow by using MLST is presented. Allele profile analysis of the studied B. pertussis strains was performed, 4 sequence types (ST) were identified--ST1, ST2, ST3 and ST5, most of the circulating strains (86.7%) were shown to belong to ST5, equal percentage of cases (5.7%)--to ST2 and ST3, and 1.9%--to ST1, while 2 vaccine production strains belong to ST2 and 1 - to ST1. CONCLUSION: Clonal structure of contemporary Moscow strains was shown to be different from strain structure used for the production of DTP vaccine.

[Isotypes of anti-pertussis antibodies in pertussis patients at different stages of the disease].

AIM: Evaluation of anti-pertussis antibodies in pertussis patients at different stages after the onset of the disease. MATERIALS AND METHODS: Levels of IgG, IgG1, IgG2, IgG3, IgG4, IgA and IgM antibodies against the antigen complex of pertussis were evaluated by enzyme immunoassay (EIA). Sera samples were analyzed from 208 pertussis patients examined from week 1 to 10 after the onset of the disease. RESULTS: 51%, 82% and 86% pertussis patients, and 67%, 72% and 78% patients examined from week 1 to 3 after the onset of the disease had increased levels of IgM, IgA and IgG antibodies respectively. 85%, 70%, 74% and 68% pertussis patients, and 76%, 57%, 87%, 57% patients examined from week 1 to 3 after the onset of the disease had increased IgG1, IgG2, IgG3 and IgG4 levels respectively. 92% of all examined pertussis patients and 83% of patients examined from week 1 to 3 after the onset of the disease had an overall increase of anti-pertussis antibody levels. Increased level of IgM antibodies was detected predominately from week 1 to 5 after the onset of the disease. Most of the patients examined from week 3 to 10 after the onset of the disease had increased levels of IgA, IgG, IgG1, IgG2 and IgG4 antibodies, and IgG3 antibody level was increased predominately in patients examined from week 2 to 6 after the onset of the disease. CONCLUSION: Serological indicators of pertussis measured by EIA were observed in 83% of the patients examined at the early stages after the onset of the disease. Simultaneous measurement of IgA, IgG and IgM antibody levels is the most effective approach for serological diagnostics of pertussis due anti-pertussis antibodies isotype composition heterogeneity at different stages after the onset of the disease. Increased levels of IgM and IgG3 antibodies are serologic indicators of the acute phase of pertussis infection.

[Serological activity of vaccine and circulating Bordetella pertussis strains].

AIM: To study activity of vaccine and circulating strains of Bordetella pertussis in serological reactions with serum samples from healthy vaccinated children and children with pertussis infection. MATERIALS AND METHODS: One hundred forty-six serum samples from children with pertussis infection as well as 158 samples from healthy vaccinated children aged 3 - 5 years old were studied. Serologic activity of 3 vaccine strains and 7 strains of B. pertussis isolated from patients with pertussis in 2001 - 2005 against sera of children with pertussis infection or vaccinated children was assessed with hemagglutination assay (HA), radial gel immunodiffusion (RGI), and immunoelectrophoresis (IEP). RESULTS: In HA both serum samples of infected and vaccinated children were equally active in agglutination of microbial preparations prepared from vaccine or recently isolated strains of B. pertussis. RGI assay showed that 81 - 84% of serum samples from infected children and 17 -19% of samples from healthy vaccinated children reacted with vaccine strains, and 81 - 85% of samples from infected children and 16 - 20% of samples from healthy vaccinated children reacted with circulating strains: Sera from patients with pertussis formed identical lines of precipitation with vaccine and circulating strains in RGI assay and three types of precipitation arches profile in IEP. Sera from healthy vaccinated children formed identical precipitation arches with vaccine and circulating strains in RGI assay and one type of precipitation arches profile in IEP. CONCLUSION: Antibodies of patients with pertussis were equally active against vaccine and circulating strains of B. pertussis. Antibodies of vaccinated children were also equally active against vaccine and circulating strains although revealed more narrow spectrum of antigens compared to children with pertussis infection.

[Production of pertussis toxin by Bordetella pertussis strains isolated from patients with whooping cough].

AIM: To assess level of pertussin toxin (PT) production by vaccine strains of Bordetella pertussis and strains isolated from patients with whooping cough. MATERIALS AND METHODS: Concentration of PT in supernatants of microbial cultures of 3 vaccine strains and 25 strains of B. pertussis isolated from patients with pertussis in 2001 - 2005 was measured with enzyme immunoassay using gamma-globulin fractions of rabbit antiserum to PT as immunosorbent or included in peroxidase conjugates. RESULTS: Level of PT production by strains isolated from infected persons varied from 3 +/- 0.5 to 64.8 +/- 12.2 ng/MFU/ml: in 9 strains--from 3 +/- 0.5 to 9.4 +/- 2.1 ng/MFU/ml, in 7--10.5 +/- 1.8 to 18.4 +/- 2.6 ng/MFU/ml, and in 9--23.6 +/- 4.5 to 64.8 +/- 12.2 ng/MFU/ml. CONCLUSION: B. pertussis strains isolated from patients were heterogeneous on level of PT production. Difference in expression of PT between strains were as high as 20-fold. Conditionally low, moderate and high levels of PT production had 9 (36%), 7 (28%), and 9 (36%) of 25 studied strains. Three vaccine strains had levels of toxin production similar to recently isolated strains with moderate level of its production.

[Molecular genetic features of structure of gene coding tracheal colonization factor in Bordetella pertussis strains].

AIM: Comparative analysis of structure of tcfA gene coding tracheal colonization factor of Bordetella pertussis strans isolated in Moscow from patients with pertussis. MATERIALS AND METHODS: Ninety-seven strains of B. pertussis isolated in different periods of pertussis infection epidemic process (1948 - 1989--from collection of Gabrichevsky Moscow Research Institute of Epidemiology and Microbiology; 1990 - 2007--isolated in Moscow from patients with pertussis) were studied. Primers for amplification of tcfA gene region with size 945 n.p. were used. Amplicons obtained in PCR were used for sequencing. Nucleotide sequences of tcfA gene types of B. pertussis strains were matched to EMBL/GenBank database. RESULTS: Sequencing of tcfA gene fragments revealed two sequence variants. Ninety-six of 97 studied B. pertussis strains had the same sequence variant--variant 1. The one strain was characterized by other nucleotide sequence--variant 2, which differed from variant 1 by presence of insertion g in position 396 that led to reading frame shift. CONCLUSION: The structure of tcfA gene circulating population of B. pertussis strains is homogenous and is characterized by presence of "vaccine" allele dominating in majority of countries in the world.

[A direct accelerated method for detection of a whooping cough pathogen].

The developed direct method for the laboratory diagnosis of pertussis, which is based on isothermal amplification technologies, has a high (100%) specificity and sensitivity (102 m.cl.), can detect the pathogen of the disease just in the clinical sample from a patient within 7-8 hours after start of the study. The clinical trials conducted at Infectious Diseases Hospital One (Moscow) on examination of 103 patients (63 patients with the clinical diagnosis of pertussis and 40 with other respiratory tract diseases) provided evidence its high specificity and diagnostic efficiency as compared with a bacteriological test, the efficiency in different clinical types of the disease and during examinations of patients in different periods after the onset of the disease, as well as during examinations of patients with suspected pertussis and pertussis-like diseases.

[Distribution of specific IgG subclasses in patients with pertussis and in healthy persons].

AIM: To assess level of IgG1, IgG2, IgG3, and IgG4 to complex of antigens of Bordetella pertussis in patients with whooping cough and healthy children and adults. MATERIALS AND METHODS: Levels of anti-pertussis IgG subclasses in sera of patients with pertussis and healthy children and adults were measured with solid phase immunoenzyme assay using peroxidase-conjugated monoclonal antibodies to human IgG1, IgG2, IgG3, and IgG4. RESULTS: In patients with pertussis, IgG1-IgG3-IgG2-IgG4 type of distribution of subclasses with predominance of IgG1 and IgG3 was revealed. In healthy children and adults the character type of subclasses distribution was IgG1-IgG2-IgG4 with absent or low level of IgG3. CONCLUSION: Detection of specific IgG3 mainly in patients with pertussis allows to consider them as a reliable serological sign of pertussis infection.

[Improvement of pertussis diagnostics in adults with prolonged cough].

AIM: To study clinical and laboratory data and levels of IgG, IgG1, IgG2, IgG3, IgG4, IgA and IgM to Bordetella pertussis complex of antigens in adults with prolonged cough. MATERIALS AND METHODS: Antibody levels to Bordetella pertussis complex of antigens were measured by solid phase immunoenzyme assay. Clinical and laboratory methods included CBC, chest X-ray, measurement of respiratory function, allergologic tests. RESULTS: In 16 out of 75 studied patients (21%) serological signs that are characteristic for current pertussis infection (increased levels of specific IgG and IgA as well as IgG1 - IgG3 - IgG2 - IgG4 type of distribution of specific IgG subclasses) were observed. Clinical and laboratory parameters--course of disease, characteristics of cough, results of CBC--corresponded to diagnosis of pertussis. In other studied patients levels of specific antibodies did not differ from levels observed in healthy persons and observed clinical signs corresponded to other respiratory diseases. CONCLUSION: Obtained results prove the high incidence of pertussis in adults, its essential importance as etiologic factor of prolonged cough and high informative value of serologic tests.

[Polymorphism of tox and dtxR genes in circulating strains of Corynebacterium diphtheriae].

Polymorphism of tox and dtxR genes responsible for diphtheria toxin synthesis was revealed. Seven point mutations in tox gene were detected; study of their combinations allowed to determine 10 allelic variants of the tox gene in C. diphtheriae strains. Majority of mutations did not lead to changes in substitutions in amino acid sequence of diphtheria toxin. In tox gene from 2 strains of mitis biovar, ribotype "Otchakov" isolated in Saint-Petersburg, mutation in position 1252 (G --> C), which corresponds to change of glycine on arginine in amino acid sequence of diphtheria toxin (G393R), was identified. Mutation localizes in R domain of fragment B of diphtheria toxin. In the dtxR gene 16 point mutations were registered; study of their combinations allowed to determine 10 allelic variants of the dtxR gene. Two mutations led to amino acid substitutions in regulatory protein DtxR: in position 640 (C --> A), which corresponds to change of leucine on isoleucine (L2141), and in position 440 (C --> T), which corresponds to change of alanine on valine (A147V). Mutation A147V is characteristic for all strains of epidemic clonal group (strains of biovar gravis, ribotype "Sankt-Peterburg/Rossija", enzyme types of complex 8), dominated in Russia during diphtheria epidemic at 1990s. Strains of this group were characterized by high level of diphtheria toxin production.

[Humoral immunity against pertussis and its prevalence in population].

Levels of IgG and IgA to complex of Bordetella pertussis antigens were assessed in 503 healthy children aged 1 - 14 years, 75 adolescents aged 15 - 17 years, and in 504 adults aged 18 - 54 years. The highest level of IgG was observed in children aged < 5 years. In older age groups progressive decrease of IgG level was noted, which more most prominent in 9 - 11 year-olds with subsequent stabilization of the level in adolescents and adults. Significant heterogeneity of IgG level was noted in all age groups. Rate of detection of increased IgA level correlated with age-related decrease of IgG level and increased from 2 - 5% in children aged 1 - 5 years to 12 - 16% in older children and adults. Obtained data point to low levels of immunity against pertussis in older children, adolescents and adults and high undetected incidence of pertussis in studied population.

[Antigenic composition and serologic characteristics of domestic acellular pertussis vaccine].

AIM: To assess antigenic composition consistency and serological characteristics of domestic acellular pertussis vaccine. MATERIALS AND METHODS: Amount of pertussis toxin, filamentous hemagglutinin, agglutinogens types 1, 2, and 3 in experimental batches of vaccine was measured by enzyme immunoassay. Levels of antibodies to aforementioned antigens as well as to lipopolysaccbaride in serum samples obtained from patients with pertussis and healthy vaccinated children were measured by the same method. The amount of lypopolysaccharide was determined by LAL test. RESULTS: Studied batches of vaccine were standard on amount of all protein antigens as well as lipopolysaccharide. Spectrum of antibodies to vaccine components in serum samples from patients with pertussis and healthy vaccinated children included antibodies to individual antigens: pertussis toxin, filamentous hemagglutinin, lipopolysaccharide, agglutinogens types 1, 2, and 3. CONCLUSION: Developed technology for manufacturing acellular pertussis vaccine allows to consistently produce preparations with standard amount of all components. Vaccine components interact with antibodies to wide spectrum of B. pertussis antigens.

[Dynamics of changes in pathogenic characteristics of Bordetella pertussis strains].

AIM: To study pathogenic characteristics of B. pertussis strains isolated from patients during different periods of pertussis infection epidemic process. MATERIALS AND METHODS: Strains of B. pertussis isolated in Moscow during 1967 - 1971, 1980 - 1985, and 2001 - 2005 were studied. Nutrient media: Bordet-Gengou blood agar, casein-charcoal agar. ANIMALS: mice - F1 hybrids (CBA x C57BL6). Pathogenic characteristics of strains were studied by assessment of virulence (LD50), leukocytosis-stimulating (LS units) and histamine-sensitizing (HSD50) activities of cultures. Genotyping was performed using standard equipment and reagents for DNA isolation, amplification, sequencing and detection of results. RESULTS: On the sample of 164 strains, pathogenic and genotypic characteristics of B. pertussis populations circulated during 1967 - 1971, 1980 - 1985, and 2001 - 2005. Majority of B. pertussis strains isolated in 1967 - 1971 and strains circulated during current phase of epidemic process were virulent (80.75% and 81.8% respectively) and had significant leukocytosis-stimulating and histamine-sensitizing activity, whereas strains isolated from patients with pertussis in 1980 - 1985 characterized by lower virulence and toxicity. Genotyping showed strains carrying "non-vaccine" allele ptxA1, which emerged in the middle of 1970s, totally displaced strains with "vaccine" alleles ptxA2 and ptxA4. CONCLUSION: Adaptive changes of B. pertussis driven by increased vaccination coverage involve both ptxA gene and pathogenic characteristics of infectious agent in the range of genotypically homogenous population with domination of strains, which have high levels of virulence and toxicity.

[Molecular genetic method of rapid detection of Bordetella pertussis strains are possessed of different ptx genes].

Features of structure of different B. pertussis genes are studied in many countries of the world, and, first of all, ptxA gene, which encodes main protective antigen of the microbe--pertussis toxin. Starting from 1980s, B. pertussis strains with new "non-vaccine" allele ptxA1 gradually displaced strains with old "vaccine" alleles--ptxA2 and ptxA4, and now the formers dominate in circulating bacterial population. Molecular genetic method of rapid identification of B. pertussis strains, based on the differences in ptxA gene structure, was developed. The method using phenomenon of endonuclease restriction can be applied for differentiation of B. pertussis from B. parapertussis strains in diagnostic purposes.

[Direct nitrate reductase method of assessment of Mycobacterium tuberculosis susceptibility to drug].

Microbiological method of direct accelerated assessment of resistance of Mycobacterium tuberculosis to rifampicin and isoniazide was developed which is able to detect multidrug resistant M. tuberculosis 10-21 days after obtaining of sputum--4-5 times faster compared with the method of absolute concentrations. Efficacy of the method was 0.93 and 0.96 during assessment of susceptibility to rifampicin and isoniazide respectively.

[Modern strains of Bordetella pertussis: immunobiological properties and vaccine improvement].

Strains of B. pertussis isolated from patients in Moscow in 2001-2005 as well as strains included in locally produced diphtheria-tetanus-whole cell pertussis (DTP) vaccine were studied. Nucleotide sequences in genes of pertactin and S1-subunit of pertussis toxin of isolated strains, their immunobiological properties and opportunity to use for producing of the acellular pertussis vaccine were determined. Genes of pertactin and S1-subunit of pertussis toxin in the isolated wild strains differed from the same genes in strains included in the local DTP vaccine. Majority of the isolated strains belonged to serotype 1.0.3 and were markedly virulent.

[Molecular genetic characteristics of the B. pertussis strains isolated in different periods of the pertussis epidemic process].

Despite the fact that the mass immunization of the children population with the DPTs vaccine has been carried out in the Russian Federation since 1959, the pertussis infection persists to be one of the pressing problems for the children population. Although the vaccination coverage of the children population with pertussis vaccines is high in Russia, at present time the pertussis incidence rates are increasing among schoolchildren and remain high among infants younger than 12 months old. Many researchers believe that the variability of the genetic structure of the pertussis causative agent may be one of the causes of increasing pertussis incidence rates. This investigation provides the molecular genetic characteristics of 97 B. pertussis strains isolated in pertussis patients in Moscow in different periods of pertussis epidemic process since the 1950s up to present time. It shows the changes in the structures of genes, which are encoding the main protective antigens of the pertussis microbe that are the pertussis toxin (ptxS1) and the pertactin (pm). The structurre of the ptxS1 and pm gene of the B. pertussis vaccine strains was compared with the structures of these genes in the B. pertussis strains isolated from the pertussis patients at present time and also in past years. All B. pertussis strains isolated in the prevaccination period (1948-1959) and most strains (95%) isolated during the first twenty years of the mass immunization in Russia are characterized by the presence of the so called "vaccine" alleles of the pertussis toxin and pertactin genes that are ptxS1 B or ptxS1 D and pm 1 alleles that corresponds to the genetic structure of the vaccine producing strains. In the early 1970s the B. pertussis strains of another toxin and pertactin genetic structures with so-called "non-vaccinal" alleles ptxS1 A and pm 3 (pm 2 since 1980s) began to appear. The B. pertussis strains with "non-vaccinal" alleles have completely displaced the "old" strains. At present time in Moscow the pertussis disease is caused by the B. pertussis strains bearing ptxS1 A and pm 2 or pm 3 alleles of pertussis toxin and pertactin genes. There was no correlation between the genotype and serotype. Thus, the structure of the B. pertussis toxin and pertactin genes in strains which have been isolated since the 1980s up to now differs from the structure of these genes in strains which are used for producing DPTs vaccine. The data obtained in this investigation suggest that the genetic structure specificity of circulating B. pertussis strains that are producing the disease at present time should be used as one of the criteria for selecting vaccine producing strains.

[Epidemic process of pertussis in Moscow].

Materials reflecting the dynamics of pertussis morbidity during the period of 1958 - 2003 under the conditions of prolonged mass immunization of the child population with adsorbed DPT vaccine are presented. The planned vaccination of children led to the decrease of pertussis morbidity during the first 10 years, but groundless abstentions from vaccination during the 1980s - 1990s contributed to a sharp rise in morbidity among children of younger age groups. During the recent four years a rise in pertussis morbidity was registered in 2000 (71.79 per 100,000 of the population), followed by the most significant for the last 20 years drop in morbidity in 2002--down to 9.89. But in 2003 the growth of morbidity was again registered (38.67). Recently periodic rises and drops in morbidity occurred simultaneously with the increased coverage of children of younger age groups with vaccination. In recent years changes in the age structure of patients were observed: the specific proportion of school children increased (in 2003 morbidity rates in children aged 6 - 10 years were 288.6 - 270.7), simultaneously high morbidity among children aged up to one year (274.9) was registered. The specific proportion of pertussis-affected children aged above 7 years reached 65%. From the late 1990s until present in 87.1% of cases strains of serotype 1.0.3 prevailed in the population of B. pertussis strains. But in recent years the circulation of strains 1.2.3, spread in the prevaccination period and having toxicity similar to that of strains of serotype 1.0.3, while exceeding them in virulence, in sufficiently high proportion (7.0% in 2002) was noted. This was indicative of the possibility of the unfavorable development of the epidemic process of pertussis infection.