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Objective. To present the data on the main mechanism of molecular variation in P. aeruginosa causing chronic lung infection in patients with cystic fibrosis. Materials and Methods. A total of 1800 throat swabs and sputum samples from cystic fibrosis patients were included in the study over the 10-year period. P. aeruginosa isolates were primarily identified by the biochemical method using the API 20NE test strips (bioMerieux, France). Antimicrobial susceptibility testing was performed by disc diffusion method. Genotyping was conducted by RAPD-PCR and MLST. Whole genome sequencing of three typical P. aeruginosa isolates was performed on an Ion PGM Torrent platform with Ion Sequencing Kit and 316v1 chips (Life Technologies Thermo Fisher, US) according to the manufacturer’s protocol. The RAST web application was used for initial annotation. Results. There were three main variants of the pathogen variability found: population heterogeneity, pathogen microevolution, and replacement by another genotype of the same species. The variation of the pathogen’s genome is due to the acquisition of mobile genetic elements (plasmids), mutations in the chromosomal genes responsible for antibiotic resistance, bacterial viability and survival during persistence in a host, and changes in the prophage regions of the pathogen. Conclusions. Epidemiological significance of the molecular mechanisms of pathogen variation is primarily due to the ability of strains to form epidemiologically significant clone. This requires control measures aimed to limit emergence and distribution of such clones to be developed.

The objective of this study was to compare the MALDI Biotyper system and the microbiological diagnosis algorithm for identification of non-fermenting bacteria isolated from respiratory tract in cystic fibrosis patients. The identification and typing algorithm, including bacteriologic, biochemical, and molecular methods as well as the MALDI Biotyper system was used. Using this algorithm, a total of 47 species of non-fermenting microorganisms was identified. The identification of microorganisms belonging to Achromobacter genus and Burkholderia cepacia complex (Bcc) proved to be the most difficult and require a combination of the methods listed above. Achromobacter species were isolated from 89 adults and children with cystic fibrosis, of which 82.7% and 10.6% belonged to Achromobacter ruhlandii and Achromobacter xylosoxidans, respectively. A total of 60 strains (3 species) of Bcc were isolated (32 strains – from adults and 28 strains – from children), of which 83.3% belonged to B. cenocepacia. The Bcc species were isolated from adult and pediatric patients with cystic fibrosis in Moscow (B. cenocepacia), Saint-Petersburg (B. contaminans, B. cepacia) and Khabarovsk (B. cepacia, B. cenocepacia, and B. contaminans). A total of 57 strains (11 species) of Pseudomonas spp. were isolated from adults and children, of which 41 strains (71.9%) were identified as P. aeruginosa (including 8 strains with atypical phenotype). P. aeruginosa proved to be an easier non-fermenting microorganism to be identified (except for isolates with atypical phenotype, where the use of MALDI-TOF mass spectrometry is critical).