Rplasmid

R plasmid, also written as R-plasmid, is a plasmid that carries one or more genes that confer resistance to antibiotics or other antimicrobial agents. These plasmids can be transferred between bacteria, often by conjugation, enabling rapid spread of resistance. The term arose from early studies on bacterial resistance in the mid-20th century; R plasmids are commonly found in Gram-negative bacteria, particularly Enterobacteriaceae such as Escherichia coli and Klebsiella species. They are a major factor in the emergence of multidrug-resistant strains in clinical settings.

Genetic structure: R plasmids typically harbor resistance genes (R genes) that can encode enzymes to inactivate drugs, modify drug targets, or pump drugs out via efflux pumps. These genes are often housed within transposons or gene cassettes embedded in integrons, allowing rapid acquisition and rearrangement of resistance. Core plasmid regions include an origin of replication (ori) and, for conjugative plasmids, a transfer region (tra) that enables transfer through a mating bridge. Many R plasmids belong to incompatibility groups (Inc) which determine compatibility with other plasmids within a cell.

Impact and control: The spread of R plasmids drives horizontal gene transfer and multidrug resistance in bacterial populations, complicating treatment of infections and necessitating surveillance and infection control. They can be lost in absence of selective pressure, but stabilizing elements such as toxin-antitoxin systems can maintain them. Detection relies on phenotypic antibiotic susceptibility testing and molecular methods (PCR, sequencing) to identify resistance determinants. Understanding R plasmids informs antibiotic stewardship and strategies to curb resistance dissemination.