Compliance with ethical standards: the study was approved by the Ethics Committee of G. N. Gabrichevsky Research Institute for Epidemiology and Microbiology. Informed consent was obtained from all participants.

Author contribution: Borisova OYu carried out molecular genetic tests, analyzed the literature and the obtained data, contributed to manuscript preparation; Chaplin AV performed phylogenetic analysis, analyzed the experimental data and contributed to manuscript preparation; Gadua NT, Pimenova AS carried out microbiological tests and contributed to manuscript preparation; Alexeeva IN, Rakitsky GF examined the patients on admission and contributed to manuscript preparation; Afanasiev SS conducted molecular genetic tests and contributed to manuscript preparation; Donskikh EE аnalyzed the literature and the experimental data and contributed to manuscript preparation; Kafarskaya LI analyzed the experimental data and contributed to manuscript preparation.