Transmissible Antibiotic Resistance

Abstract

Bacteria have developed transmissible resistance to almost every antibiotic in clinical use, both synthetic compounds and natural products. The mechanisms are well understood: antibiotic inactivation, target alteration, and drug exclusion. Some mechanisms are antibiotic specific, others class specific, and a few provide resistance to several classes of agents. Resistance genes are ancient and ubiquitous. Sources include antibiotic producers, soil cohabitants that needed protection in order to compete, and housekeeping genes that can be adapted to new uses. Transmission involves conjugative and nonconjugative plasmids, integrons, transposons, insertion sequences, and bacteriophage. Resistance enzymes can be inhibited, and antibiotics can be modified to restore activity, but bacterial enzymes can evolve to lose inhibitor sensitivity, and new mechanisms can be recruited to resist modified drugs. Resistance to available agents is increasing. New antimicrobial agents and fresh ideas are needed to overcome the declining power of our antibacterial weapons.