Potentiation of curing by a broad-host-range self-transmissible vector for displacing resistance plasmids to tackle AMR

Plasmids are potent vehicles for spread of antibiotic resistance genes in bacterial populations and often persist in the absence of selection due to efficient maintenance mechanisms. We previously constructed non-conjugative high copy number plasmid vectors that efficiently displace stable plasmids from enteric bacteria in a laboratory context by blocking their replication and neutralising their addiction systems. Here we assess a low copy number broad-host-range self-transmissible IncP-1 plasmid as a vector for such curing cassettes to displace IncF and IncK plasmids. The wild type plasmid carrying the curing cassette displaces target plasmids poorly but derivatives with deletions near the IncP-1 replication origin that elevate copy number about two-fold are efficient. Verification of this in mini IncP-1 plasmids showed that elevated copy number was not sufficient and that the parB gene, korB, that is central to its partitioning and gene control system, also needs to be included. The resulting vector can displace target plasmids from a laboratory population without selection and demonstrated activity in a mouse model although spread is less efficient and requires additional selection pressure

Development of plasmids that can displace antibiotic resistance plasmids from bacteria in the human and animal gastrointestinal tract

Antibiotic resistance is one of the greatest scientific and medical challenges of the 21st century. However, our arsenal to combat this surge is limited to a small number of antimicrobial drugs. Plasmids are major contributors to the problem, yet specifically targeting them to reduce the burden of resistant infections has not been fully exploited. It is possible to repress plasmid’s replication and eliminate them from a population by harnessing their innate replication and maintenance functions. This concept has been applied in this study to construct conjugative broad-host range plasmids aimed at curing either IncF or IncK plasmids based on IncPα RK2 and pUB307 backbones. pUB307- based pCURE gave a stronger curing phenotype as tested by a novel simple curing experiment and long-term invasion assays. The curing potentiation was investigated and found to be due to the absence of iteron 10 in $oriV$ and a resulting higher copy number. The clinical potential of the technology was demonstrated by successfully curing a novel resistance plasmid, pEK499 and by $in$ $vivo$ mice experiments where pCURE conjugated into and cured target plasmids from $E. coli$ established within the gastrointestinal tract. With further work to ensure long-term curing and biosafety, pCURE could improve the treatment options for multi-drug resistant infections