Whole-genome sequencing of strains isolated in Russia.

BACKGROUND AND AIM

is a Gram-negative bacterium belonging to the family that can cause bovine histophilosis. may act as a commensal or opportunistic bacterial cattle pathogen. Comparing genomes of the pathogenic strain 2336 with the non-pathogenic preputial 129Pt isolate revealed some putative virulence factors. The study of the complete genomes of strains circulating in Russia has never been conducted before. This study aimed to identify genetic features of the strains isolated in Russia and evaluate the possibility of using strains for vaccine development.

MATERIALS AND METHODS

Three strains of were isolated from different sources. Strain 188-VIEV was isolated from a vaginal swab sample of cattle with endometritis. 532-VIEV and 551-VIEV were cultured from the cryopreserved bull semen samples imported from Canada. strain ATCC 700025 provided by ATCC (American Type Culture Collection) was also used in the study. DNA extraction was performed using QIAamp DNA Mini Kit (QIAGEN, USA). The whole-genome sequencing of the four strains was performed using Illumina Miseq. The comparison of the resulting sequences with the complete genomes of 2336 and 129Pt, and detection of the resistance genes and virulence factors, was performed using the ResFinder and Virulence Factor Database web services.

RESULTS

The genome size of the samples varied from 1.9 to 2.3 Mb. The number of coding sequences varied from 1795 to 2256. The average sequence density was 90%. The total guanine-cytosine (GC) content was 36.8%-37.2%, which coincided with data previously obtained for . Three out of four studied strains encoded putative virulence factors such as filamentous hemagglutinin homologs, lipooligosaccharide biosynthesis proteins, and proteins involved in iron transport and utilization. The Ser83Ile substitution was identified in the DNA topoisomerase II () in strains 532-VIEV and 551-VIEV cultured from bull semen which led to resistance to fluoroquinolones. The gene ('') encoding a bifunctional aminoglycoside modification enzyme was detected in strain 551-VIEV.

CONCLUSION

Strains with virulence genes identified could be candidates for designing vaccines and potentially represent antigen sources. The results show that antibiotic-resistant can be spread with semen used for artificial insemination.