Dolejska, M. | Search bioRxiv

bioRxiv2023

Plasmid-mediated colistin resistance among human clinical Enterobacterales isolates: National surveillance in the Czech Republic

The occurrence of colistin resistance has increased rapidly among Enterobacterales around the world. We performed a national survey of plasmid-mediated colistin resistance in human clinical isolates by a retrospective analysis of samples from 2009-2017 and a prospective sampling in 2018-2020. The aim of this study was to identify and characterize isolates with mcr genes from various regions of the Czech Republic using whole genome sequencing (WGS). Of all 1932 colistin-resistant isolates analyzed, 73 (3.8%) were positive for mcr genes. Most isolates carried mcr-1 (48/73) and were identified as Escherichia coli (n=44) and Klebsiella pneumoniae (n=4) of various sequence types (ST). Twenty-five isolates including Enterobacter spp. (n=24) and Citrobacter freundii (n=1) carrying mcr-9 gene were detected, three of them (Enterobacter kobei ST54) co-harbored the mcr-4 and mcr-9 genes. Multi-drug resistance phenotype was a common feature of mcr isolates and 14% (10/73) isolates also co-harboured clinically important beta-lactamases including 2 isolates with carbapenemases KPC-2 and OXA-48. Phylogenetic analysis of E. coli ST744, the dominant genotype in this study, with the global collection, showed Czech isolates belonged to two major clades, one containing isolates from Europe, while the second composed of isolates from diverse geographical areas. The mcr-1 gene was carried by IncX4 (34/73, 47%), IncHI2/ST4 (6/73, 8%) and IncI2 (8/73, 11%) plasmid groups. Small plasmids belonging to the ColE10 group were associated with mcr-4 in three isolates while mcr-9 was carried by IncHI2/ST1 plasmids (4/73, 5%) or the chromosome (18/73, 25%). We showed an overall low level of occurrence of mcr genes in colistin-resistant bacteria from human clinical samples in the Czech Republic.

microbiology↗

bioRxiv2021

Fitness effects of CTX-M-15-encoding IncF plasmids on their native Escherichia coli ST131 H30Rx hosts

ObjectivesThe objective of this study was to investigate effects of large CTX-M-15-encoding IncF plasmids on the fitness of their native E. coli ST131 H30Rx hosts in order to understand possible plasmid-host coevolution. MethodsWe selected five E. coli ST131 H30Rx strains of diverse origin, each carrying a multireplicon IncF plasmid encoding the gene blaCTX-M-15. The plasmid was eliminated from each isolate by displacement using an incompatible plasmid vector pMDP5_cureEC958. Whole-genome sequencing (WGS) was performed to obtain complete chromosome and plasmid sequences of wild-type isolates and to detect chromosomal mutations in plasmid-free strains. Competition assays were conducted to determine the relative fitness of plasmid-free clones compared to the corresponding wild-type isolates. ResultsWe were able to successfully eliminate the IncF plasmids from all of the wild-type strains using the curing vector pMDP5_cureEC958. The chromosomes of plasmid-free clones contained zero to six point mutations. Plasmid-free strains of three isolates showed no significant difference in relative fitness compared to the corresponding plasmid-free strains. In the two remaining isolates, the plasmids produced a small but significant fitness cost. ConclusionWe conclude that IncF plasmids produce moderate fitness effects in their E. coli ST131 H30Rx hosts. This fitness compatibility is likely to promote the maintenance of antibiotic resistance in this worrisome E. coli lineage.

evolutionary biology↗