Molecular biological features of Streptococcus agalactiae strains isolated from pregnant women and women in labor in various regions of the Russian Federation

Objective.

To study molecular biological features of Streptococcus agalactiae strains isolated from pregnant women and women in labor in various regions of the Russian Federation.

Materials and Methods.

The study included 205 S. agalactiae strains isolated from pregnant women and women in labor in various regions of the Russian Federation for the period 2022–2023. The strains were isolated from vaginal rectal smears of pregnant women during screening at 35–37 weeks of gestation and from vaginal discharge of women in labor. Whole-genome sequencing data were obtained for each strain using high-throughput nucleotide sequencing. The bioinformatic analysis was carried out: genome assembly, multi-locus sequence typing (MLST), serotype determination of strains based on whole-genome sequencing data, detection of antimicrobial resistance genes, plasmid profile analysis, detection and analysis of mobile genetic elements.

Results.

The whole-genome sequencing data of 205 strains of S. agalactiae isolated from pregnant women, women in labor in various regions of the Russian Federation were obtained and their bioinformatic analysis was carried out. During serotyping, seven different serotypes were identified: Ia, Ib, II, III, IV, V, VI. Serotypes V (30.7%), III (28.3%), Ia (15.6%) were detected most often, serotypes II (9.8%), Ib (7.8%), IV (5.9%) and VI (1.9%) were less common. 28 different sequence types were identified, the following sequence types were most common: ST17 (14.6%), ST1 (12.7%), ST890 (11.2%), ST23 (7.3%), ST28 (5.9%), ST88 (5.4%), totaling more than 55% of all studied strains. The strains with sequence types belonging to five clonal complexes were most often identified: CC19 (18.5%), CC1 (17.1%), CC23 (16.1%), CC17 (15.1%) and CC452 (14.1%). Two different genes of resistance to aminoglycosides have been found in 51 strains – ant(6)-Ia, aph(3’)-III; five genes of resistance to macrolides and/or lincosamides have been found in 119 strains – ermA, ermB, msrD, lsaC, mefA; two tetracycline resistance genes have been found in 188 strains – tetM and tetO and two chloramphenicol resistance genes have been found in 13 strains – cat, catQ, no vancomycin resistance genes have been found. Analyzing of the plasmid profile in Streptococcus agalactiae strains, one plasmid – repUS43 was identified, its incidence was 38.0%. 27 different types of mobile genetic elements with different frequencies were detected.

Conclusions.

S. agalactiae strains isolated from pregnant women and women in labor in various regions of the Russian Federation have different serotypes and sequence types occurring with different frequencies, and possess a spectrum of antimicrobial resistance genes and mobile genetic elements.