Plasmid-mediated resistance is the transfer of antibiotic resistance genes which are carried on plasmids. Plasmids possess mechanisms that ensure their independent replication as well as those that regulate their replication number and guarantee stable inheritance during cell division. By the conjugation process, they can stimulate lateral transfer between bacteria from various genera and kingdoms. Numerous plasmids contain addiction-inducing systems that are typically based on toxin-antitoxin factors and capable of killing daughter cells that don't inherit the plasmid during cell division. Plasmids often carry multiple antibiotic resistance genes, contributing to the spread of multidrug-resistance (MDR). Antibiotic resistance mediated by MDR plasmids severely limits the treatment options for the infections caused by Gram-negative bacteria, especially family Enterobacteriaceae. The global spread of MDR plasmids has been enhanced by selective pressure from antimicrobial medications used in medical facilities and when raising animals for food. Properties of resistance plasmids Resistance plasmids by definition carry one or more antibiotic resistance genes. They are frequently accompanied by the genes encoding virulence determinants, specific enzymes or resistance to toxic heavy metals. Multiple resistance genes are commonly arranged in the resistance cassettes. The antibiotic resistance genes found on the plasmids confer resistance to most of the antibiotic classes used nowadays, for example, beta-lactams, fluoroquinolones and aminoglycosides. It is very common for the resistance genes or entire resistance cassettes to be re-arranged on the same plasmid or be moved to a different plasmid or chromosome by means of recombination systems. Examples of such systems include integrons, transposons, and ISCR-promoted gene mobilization. Most of the resistance plasmids are conjugative, meaning that they encode all the needed components for the transfer of the plasmid to another bacterium, and that isn't present in mobilizable plasmids. According to that, Mobilizable plasmids are smaller in size (usually < 10 kb) while conjugative plasmids are largger (usually > 30 kb) due to the considerable size of DNA required to encode the conjugation mechanisms that allow for cell-to-cell conjugation. R-factor R-factors are also called a resistance factors or resistance plasmid,They are tiny, circular DNA elements that are self-replication, that contain antibiotic resistance genes. They were first found in Japan in 1959 when it was discovered that some Shigella strains had developed resistance to a number of antibiotics used to treat a dysentery epidemic. Shigella is a genus of Gram-negative, aerobic, non-spore-forming, non-motile, rod-shaped bacteria. Resistance genes are ones that give rise to proteins that modify the antibiotic