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K Chumakov

Publications and source records attributed to K Chumakov.

9 recordsLinked to original sources
PubMed2003

Microarray analysis of erythromycin resistance determinants.

AIMS: To develop a DNA microarray for analysis of genes encoding resistance determinants to erythromycin and the related macrolide, lincosamide and streptogramin B (MLS) compounds. METHODS AND RESULTS: We developed an oligonucleotide microarray containing seven oligonucleotide probes (oligoprobes) for each of the six genes (ermA, ermB, ermC, ereA, ereB and msrA/B) that account for more than 98% of MLS resistance in Staphylococcus aureus clinical isolates. The microarray was used to test reference and clinical S. aureus and Streptococcus pyrogenes strains. Target genes from clinical strains were amplified and fluorescently labelled using multiplex PCR target amplification. The microarray assay correctly identified the MLS resistance genes in the reference strains and clinical isolates of S. aureus, and the results were confirmed by direct DNA sequence analysis. Of 18 S. aureus clinical strains tested, 11 isolates carry MLS determinants. One gene (ermC) was found in all 11 clinical isolates tested, and two others, ermA and msrA/B, were found in five or more isolates. Indeed, eight (72%) of 11 clinical isolate strains contained two or three MLS resistance genes, in one of the three combinations (ermA with ermC, ermC with msrA/B, ermA with ermC and msrA/B). CONCLUSIONS: Oligonucleotide microarray can detect and identify the six MLS resistance determinants analysed in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results suggest that microarray-based detection of microbial antibiotic resistance genes might be a useful tool for identifying antibiotic resistance determinants in a wide range of bacterial strains, given the high homology among microbial MLS resistance genes.

Anti-Bacterial Agents↗
PubMed2002

Detection and genotyping of human group A rotaviruses by oligonucleotide microarray hybridization.

A rapid and reliable method for the identification of five clinically relevant G genotypes (G1 to G4 and G9) of human rotaviruses based on oligonucleotide microarray hybridization has been developed. The genotype-specific oligonucleotides immobilized on the surface of glass slides were selected to bind to the multiple target regions within the VP7 gene that are highly conserved among individual rotavirus genotypes. Rotavirus cDNA was amplified in a PCR with primers common to all group A rotaviruses. A second round of nested PCR amplification was performed in the presence of indodicarbocyanine-dCTP and another pair of degenerate primers also broadly specific for all genotypes. The use of one primer containing 5'-biotin allowed us to prepare fluorescently labeled single-stranded hybridization probe by binding of another strand to magnetic beads. The identification of rotavirus genotype was based on hybridization with several individual genotype-specific oligonucleotides. This approach combines the high sensitivity of PCR with the selectivity of DNA-DNA hybridization. The specificity of oligonucleotide microchip hybridization was evaluated by testing 20 coded rotavirus isolates from different geographic areas for which genotypes were previously determined by conventional methods. Analysis of the coded specimens showed that this microarray-based method is capable of unambiguous identification of all rotavirus strains. Because of the presence of random mutations, each individual virus isolate produced a unique hybridization pattern capable of distinguishing different isolates of the same genotype and, therefore, subgenotype differentiation. This strain information indicates one of several advantages that microarray technology has over conventional PCR techniques.

Antigens, Viral↗
PubMed2001

Quantitative mutant analysis of viral quasispecies by chip-based matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry.

RNA viruses exist as quasispecies, heterogeneous and dynamic mixtures of mutants having one or more consensus sequences. An adequate description of the genomic structure of such viral populations must include the consensus sequence(s) plus a quantitative assessment of sequence heterogeneities. For example, in quality control of live attenuated viral vaccines, the presence of even small quantities of mutants or revertants may indicate incomplete or unstable attenuation that may influence vaccine safety. Previously, we demonstrated the monitoring of oral poliovirus vaccine with the use of mutant analysis by PCR and restriction enzyme cleavage (MAPREC). In this report, we investigate genetic variation in live attenuated mumps virus vaccine by using both MAPREC and a platform (DNA MassArray) based on matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Mumps vaccines prepared from the Jeryl Lynn strain typically contain at least two distinct viral substrains, JL1 and JL2, which have been characterized by full length sequencing. We report the development of assays for characterizing sequence variants in these substrains and demonstrate their use in quantitative analysis of substrains and sequence variations in mixed virus cultures and mumps vaccines. The results obtained from both the MAPREC and MALDI-TOF methods showed excellent correlation. This suggests the potential utility of MALDI-TOF for routine quality control of live viral vaccines and for assessment of genetic stability and quantitative monitoring of genetic changes in other RNA viruses of clinical interest.

Animals↗
PubMed2001

Correlation of genetic variability with safety of mumps vaccine Urabe AM9 strain.

The Urabe AM9 strain of mumps vaccine live is known for its genetic instability and some vaccines derived from this strain were withdrawn from the market due to an excessive number of vaccine-associated parotitis and meningitis cases. To identify the molecular basis of this instability, we determined complete nucleotide sequences of several stocks of the Urabe strain used for vaccine production by different manufacturers and of two clinical isolates from cases of vaccine-associated meningitis. In contrast to previously published studies relating the Lys335 --> Glu mutation in the viral HN gene with neurovirulence of mumps virus, we could not confirm any association of this mutation with the safety of mumps vaccine. Each of the three vaccine stocks studied had its own characteristic profile of mutations that was identified by cDNA sequencing and quantitated by mutant analysis by PCR and restriction enzyme cleavage. Determination of the mutational profile of mumps vaccine lots could allow vaccine manufacturers to characterize seed viruses and monitor the consistency of vaccine production to prevent emergence of virulent revertants.

Amino Acid Substitution↗
PubMed2001

Microarray analysis of microbial virulence factors.

Hybridization with oligonucleotide microchips (microarrays) was used for discrimination among strains of Escherichia coli and other pathogenic enteric bacteria harboring various virulence factors. Oligonucleotide microchips are miniature arrays of gene-specific oligonucleotide probes immobilized on a glass surface. The combination of this technique with the amplification of genetic material by PCR is a powerful tool for the detection of and simultaneous discrimination among food-borne human pathogens. The presence of six genes (eaeA, slt-I, slt-II, fliC, rfbE, and ipaH) encoding bacterial antigenic determinants and virulence factors of bacterial strains was monitored by multiplex PCR followed by hybridization of the denatured PCR product to the gene-specific oligonucleotides on the microchip. The assay was able to detect these virulence factors in 15 Salmonella, Shigella, and E. coli strains. The results of the chip analysis were confirmed by hybridization of radiolabeled gene-specific probes to genomic DNA from bacterial colonies. In contrast, gel electrophoretic analysis of the multiplex PCR products used for the microarray analysis produced ambiguous results due to the presence of unexpected and uncharacterized bands. Our results suggest that microarray analysis of microbial virulence factors might be very useful for automated identification and characterization of bacterial pathogens.

Bacterial Proteins↗
PubMed2000

Analysis of mutations in oral poliovirus vaccine by hybridization with generic oligonucleotide microchips.

This paper describes use of a new technology of hybridization with a micro-array of immobilized oligonucleotides for detection and quantification of neurovirulent mutants in Oral Poliovirus Vaccine (OPV). We used a micro-array consisting of three-dimensional gel-elements containing all possible hexamers (total of 4096 probes). Hybridization of fluorescently labelled viral cDNA samples with such microchips resulted in a pattern of spots that was registered and quantified by a computer-linked CCD camera, so that the sequence of the original cDNA could be deduced. The method could reliably identify single point mutations, since each of them affected fluorescence intensity of 12 micro-array elements. Micro-array hybridization of DNA mixtures with varying contents of point mutants demonstrated that the method can detect as little as 10% of revertants in a population of vaccine virus. This new technology should be useful for quality control of live viral vaccines, as well as for other applications requiring identification and quantification of point mutations.

DNA Mutational Analysis↗
PubMed1997

TgPVR21 mice for testing type-3 oral poliovirus vaccines: role of clinical observation and histological examination.

Transgenic mice susceptible to poliovirus (TgPVR mice) have been used to study poliovirus neurovirulence and attenuation. It was shown recently that mouse line TgPVR21 may be a suitable model to evaluate neurovirulence safety of oral poliovirus vaccine. It was important to determine whether TgPVR21 mice are sensitive enough to discriminate between type-3 reference and 'marginal' vaccines, i.e. those that failed the monkey test while containing only slightly increased amounts of neurovirulent revertants at position 472 of the viral genome as measured by a molecular assay MAPREC. Data presented here demonstrate that TgPVR21 mice are not less sensitive than monkeys in the detection of marginal vaccines. In contrast to the monkey neurovirulence test, which is based on histological examination of the CNS, the TgPVR21 mouse neurovirulence test revealed marginal vaccines by simple analysis of clinical signs without requiring a laborious histological examination.

Animals↗
PubMed1993

Assessment of the viral RNA sequence heterogeneity for control of OPV neurovirulence.

By using sensitive mutant analysis by PCR and restriction enzyme cleavage we have found that among several positions that differ between the wild-type and attenuated type 3 poliovirus genomes, only two positions, 472 and 2493, showed variability in vaccine lots. Of these two, only position 472 correlates with neurovirulence in monkeys, while the abundance of revertants at position 2493 indicated the type of seed virus and the passage level. Conditions of cell culture influence the rate of mutant selection, suggesting that some cellular factor(s) may be involved in selection of 472-C. Determination of 472-C content predicts which vaccine lots would fail the monkey neurovirulence test. These results imply that the PCR method can be used for optimization of manufacturing conditions.

Animals↗