Allelic Polymorphism of Anthrax Pathogenicity Factor Genes as a Means of Estimating Microbiological Risks Associated with Climate Change

Abstract

Climate change brings new risks of emergence of especially dangerous diseases. The paper reports the possibility of assessing the pathogenic potential of bacteria as demonstrated by studying the allelic polymorphism of anthrax bacterium pathogenicity factor genes, which is a prerequisite for assessing the associated microbiological risks. The allelic polymorphism of the capBCADE operon (capB, capC, capA, capD, and capE genes) encoding the capsule biosynthesis proteins of Bacillus anthracis, and the acpA and acpB genes encoding the expression regulators of this operon have been studied for the first time. A number of single nucleotide polymorphisms (SNPs) were described in the strains of the studied sample, including 5 SNPs in the capB gene, 3 in capC, 4 in capA, 14 in capD, 2 in capE, and 15 in acpB, as well as 7 SNPs and one insertion in the acpA gene. As a result, the sample has been divided into sequence types for each gene and 17 genotypes, which are combinations of the identified sequence types. In silico translation of the detected alleles of the studied genes revealed three isoforms of the CapB and CapA proteins, two isoforms of the CapC and CapE proteins, six isoforms of the CapD protein, five isoforms of the AcpA protein, and four isoforms in the AcpB protein. It has been demonstrated that the SNP in the 351A → G position of capC is a marker of A.Br.Aust94 group strains. Based on the results, A.Br.Vollum group strains were divided into two subgroups. The strains in the evolutionary lines B and C differed from the line A strains by the presence of an 853G → A SNP in the acpA gene. In addition, a previously unknown variable number tandem repeat (VNTR), has been found in the acpA gene and the possibility of using it for differentiating and genotyping of B. anthracis strains has been demonstrated.

Structure and gene cluster of the O-polysaccharide of Yersinia rohdei H274-36/78

A branched O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Yersinia rohdei H274-36/78 and found to contain d-rhamnose, d-mannose, and 3,6-dideoxy-4-C-[(S)-1-hydroxyethyl]-d-xylo-hexose called yersiniose A (Yer). Partial acid hydrolysis of the O-polysaccharide eliminated Yer residues to give a modified linear polysaccharide. Studies by sugar analysis and ¹H and ¹³C NMR spectroscopy, including computational NMR analysis, enabled structure elucidation of a hexasaccharide repeating unit of the O-polysaccharide having two Yer residues attached as monosaccharide side chains. The O-antigen gene cluster of Y. rohdei H274-36/78 located between JUMPStart and galF genes contained putative genes for synthesis of precursors of two O-antigen constituents, GDP-d-Man and GDP-d-Rha, whereas genes responsible for synthesis of CDP-Yer were within the chromosome outside the O-antigen gene cluster. Glycosyltransferase genes and ABC 2 transporter genes were present in the O-antigen gene cluster, and hence the structure established is consistent with the polysaccharide synthesis gene content of the genome.

[The study of patterns of development of resistance of Staphylococcus aureus to triclosan]

The article presents the results of studying molecular genetic mechanisms of development of resistance to antiseptic Triclosan in strain Staphylococcus aureus АТСС25923. The modifcations of strain S. aureus АТСС25923 (Tr1, Tr2, Tr1С и Tr2С) are obtained resistant to 64 mg/l of Triclosan and stably preserving the given characteristic under cultivation in absence of selective pressure. The strain S. aureus Tr1was characterized by slightly delayed growth and the strain S. aureus Tr2 was characterized by growth velocity comparable with initial strain. In the Triclosan-resistant strains a mutation C284T in gene fabI was detected resulting in amino-acid replacement A95V in enzyme enoyl-acyl protein reductase FabI, triclosan target. Besides, in these strains a stably inheriting mutation was detected in genes associated with transport of substances in cell: hypothetical transport protein HlyC/CorC family transporter, protein-transporter of ions of Na+, K+, Li+ and alkali of Na+/H+ antiporter subunit F, membrane hypothetical protein and ATP-binding protein. It is demonstrated that resistance to triclosan in staphylococci is associated with acquirement of point mutations in genes of enoyl-acyl protein reductase and also in other genes related to transport of substances in bacterial cell.

[ON THE ORIGIN OF HYPERVIRULENCE OF THE CAUSATIVE AGENT OF PLAGUE]

The attempt to combine Yersinia pseudotuberculosis and Yersinia pestis into one species has been unsupported by microbiologists due to the specific features of the epidemiology and clinical presentations of their induced diseases and to basic differences in their virulence. Pseudotuberculosis is predominantly a relatively mild human intestinal infection transmitted through contaminated food and plague is an acute generalized disease with high mortality, which is most frequently transmitted by the bites of infected fleas. Y. pestis hypervirulence, the ability of single bacteria to ensure the development of predagonal bacteriemia in rodents, which is sufficient to contaminate the fleas, is one of the main events during pathogen adaptation to a new ecological niche. By analyzing the data of molecular typing of the representative kits of naturally occurring Y. pestis isolates, the authois consider the issues of formation of intraspecies groups with universal hypervirulence, as well as biovars that are highly virulent only to their major host. A strategy for searching for selective virulence factors, the potential molecular targets for vaccination and etiotropic treatment of plague, is discussed.

A small-scale experiment of using phage-based probiotic dietary supplement for prevention of E. coli traveler's diarrhea

Traveler's diarrhea (TD) is caused by Escherichia coli in 30% of cases. We have developed a phage cocktail for prophylaxis of TD caused by E.coli, Shigella flexneri, Shigella sonnei, Salmonella enterica, Listeria monocytogenes or Staphylococcus aureus, and investigated its effectiveness against infection caused by the non-pathogenic Lac (-) strain of E.coli K12 C600 in animal and human trials. On the 6th day of both animal and human trials E. coli K12 C600 strain was detected in titer of 10⁴ CFU/g of mice feces and 10⁶ CFU/g of human feces in the control (untreated) groups, while it was not detected in the samples of either of the study (phage-treated) groups. These results have great significance because the original coliphages included in the cocktail have a broad host-range including ETEC, EAEC and EHEC strains which cause severe cases of TD.

[Molecular genetic identification of Staphylococcus aureus strain, caused a foodborne illness outbreak in St. Petersburg in 2013]

BACKGROUND

Staphylococcus aureus is one of the most important human pathogens and causes over 100 nosologicalforms of diseases. The lack of data on the spread of S. aureus genetic types specific for different forms of staphylococcal infections in Russia makes it difficult to timely identify and control strains of this epidemiologically dangerous bacterial pathogen.

OBJECTIVE

The aim of the study was to carry out a molecular genetic research of S. aureus isolates obtained during a widespread foodborne illness outbreak among builders at the Pulkovo airport in St. Petersburg in 2013.

METHODS

The ability of the isolates to produce staphylococcal enterotoxins was studied by immunoenzyme techniques. Gene typing was carried out by sequence-specific primer-based PCR, as well as by sequencing genomic nucleotide sequences of two independent isolates of the pathogen.

RESULTS

An enterotoxin A gene in genomes of S. aureus isolates etiologically associated with the outbreak was identified. The production of enterotoxin A by the isolates was shown. According to the complex analysis all isolates producing staphylococcal enterotoxins were identical and constituted the S. aureus strain, sequence-type ST30 and spa-type t2509. The genome of the identified S. aureus strain carried a set of various staphylococcal toxins. The full genome sequence among other techniques revealed high levels of similarity between genomes of the strain under study and well-known reference strain S aureus MRSA 252.

CONCLUSION

The complete molecular genetic study of the S. aureus strain involved into the widespread foodborne illness outbreak was first carried out in Russia, allowing of further using the strain as a Russian reference strain to study potential epidemic outbreaks in the Russian Federation.

[Determination of critical kanamycin concentration for Mycobacterium tuberculosis in the MGIT Bactec 960 system]

The critical concentration of canamycin for the MGIT Bactec 960 system, which has been determined on a panel of the tho--roughly characterized genetically heterogeneous clinical Mycobacterium tuberculosis isolated in the Central Region of Russia, is equal to 1.25 microg/ml.

[Determining drug resistance of the clinical strains of Mycobacterium tuberculosis to pyrazinamide]

Description of the pyrazinamide-resistant clinical strains of M. tuberculosis derived from sputum of patients treated in TB clinics in Tula was made (June, 2001 - July, 2002). It was demonstrated that 30.3% (n = 91) strains were resistant to pyrazinamide. It was found out that these strains were resistant to other antituberculosis drugs in most cases. The method of PCR-sequencing was used to find the mutations in the gene pncA determining resistance to pyrazinamide. 44 different types of mutations localized in 28 codons were detected. The predominance of the mutations in 57 (13.2%), 63 (7.7%), 97 (7.7%), 12 (6.6%), 103 (6.6%) codons and in -11 (6.6%) promoter ofp ncA was observed in the pyrazinamide-resistant strains. Several new mutations determining resistance of the clinical strains of M. tuberculosis to pyrazinamide were described. A high correlation between resistance of mycobacteria to pyrazinamide and activity of pyrazinamidase was observed.

[Structure of deletions detected in the genomes of clinical Mycobacterium tuberculosis strains]

Deletions were analyzed in the genomes of four Mycobacterium tuberculosis strains isolated from the sputum of patients living in the Central Region of Russia. The strains of the Beijing family were found to have deletions affecting 40 open reading frames (ORF) and to amount to 0.7% of the genome H37Rv. Genome deletions in a strain from the Haarlem family affected 20 ORF and accounted for 0.26% of the genome H37Rv. Six of the eight deletions were located at the site of preferred cloning on the insertion element IS6110. Prophage phiRv1-associated deletion sequence 149 is the only common to the strains of both families. The deletion ends were evenly distributed among the intergenic and coding chromosome regions with an insignificant preference of the latter. The authors revealed a new deletion in strain 1540 belonging to the Haarlem family and a two-component deletion in the region RvD2. The deletions detected in the genomes of Russian Beijing strains were typical of strains from South-East Asian countries.