Mobile Oxazolidinone Resistance Genes in Gram-Positive and Gram-Negative Bacteria.

Seven mobile oxazolidinone resistance genes, including , (B), (C), (D), (E), , and , have been identified to date. The genes code for 23S rRNA methylases, which confer a multiresistance phenotype that includes resistance to phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A compounds. The and genes code for ABC-F proteins that protect the bacterial ribosomes from the inhibitory effects of oxazolidinones. The gene confers resistance to oxazolidinones and phenicols, while the gene confers elevated MICs or resistance to oxazolidinones, phenicols, and tetracycline. These oxazolidinone resistance genes are most frequently found on plasmids, but they are also located on transposons, integrative and conjugative elements (ICEs), genomic islands, and prophages. In these mobile genetic elements (MGEs), insertion sequences (IS) most often flanked the , , and genes and were able to generate translocatable units (TUs) that comprise the oxazolidinone resistance genes and occasionally also other genes. MGEs and TUs play an important role in the dissemination of oxazolidinone resistance genes across strain, species, and genus boundaries. Most frequently, these MGEs also harbor genes that mediate resistance not only to antimicrobial agents of other classes, but also to metals and biocides. Direct selection pressure by the use of antimicrobial agents to which the oxazolidinone resistance genes confer resistance, but also indirect selection pressure by the use of antimicrobial agents, metals, or biocides (the respective resistance genes against which are colocated on -, -, or -carrying MGEs) may play a role in the coselection and persistence of oxazolidinone resistance genes.