Molecular Epidemiology of -Positive and Isolates: Results from Russian Sentinel Surveillance (2013-2018).

Background: The dissemination of mobile colistin resistance () genes is a serious healthcare threat because polymyxins represent "last-line" therapeutics for multi-drug-resistant Gram-negative pathogens. This study aimed to assess the prevalence of colistin resistance and genes and characteristics of clinical () and () isolates and plasmids carrying these genes in Russia.

Methods: A total of 4324 and 4530 collected in the frame of sentinel surveillance in 2013-2018 were tested for susceptibility to colistin and other antibiotics using the broth microdilution method. genes were screened by real-time PCR. Phylogeny, genomic features and plasmids of -positive isolates were assessed using whole-genome sequencing and subsequent bioinformatic analysis.

Results: Colistin resistance was detected in 2.24% and 9.3% . Twenty-two (0.51%) and two (0.04%) from distant sites carried . Most positive isolates co-harbored ESBLs and other resistance determinants to various antibiotic classes. The -positive belonged to 16 MLST types, with ST359 being most common; belonged to ST307 and ST23. was carried mainly in IncI2 ( = 18) and IncX4 ( = 5) plasmids highly similar to those identified previously in human, animal and environmental isolates.

Conclusion: This study demonstrated a dissemination of "typical" -bearing plasmids among diverse and genotypes and across a wide geographic area in Russia. Given the frequent association of with other resistance determinants and potential clinical impact, the continual surveillance of this threat is warranted.