What Antimicrobial Resistance Has Taught Us About Horizontal Gene Transfer

Abstract

Horizontal gene transfer (HGT) has been responsible for the dissemination of numerous antimicrobial-resistance determinants throughout diverse bacterial species. The rapid and broad dissemination of resistance determinants by HGT, and subsequent selection for resistance imposed by the use of antimicrobials, threatens to undermine the usefulness of antimicrobials. However, vigilant surveillance of the emerging antimicrobial resistance in clinical settings and subsequent studies of resistant isolates create a powerful system for studying HGT and detecting rare events. Two of the most closely monitored phenotypes are resistance to beta-lactams and resistance to fluoroquinolones. Studies of resistance to these antimicrobials have revealed that (1) transformation occurs between different species of bacteria including some recipient species that were not previously known to be competent for natural transformation; (2) transduction may be playing an important role in generating novel methicillin-resistant Staphylococcus aureus (MRSA) strains, although the details of transferring the SCCmec element are not yet fully understood; (3) Resistance genes are probably moving to plasmids from chromosomes more rapidly than in the past; and (4) Resistance genes are aggregating upon plasmids. The linkage of numerous resistance genes on individual plasmids may underlie the persistence of resistance to specific antimicrobials even when use of those antimicrobials is discontinued. Further studies of HGT and methods for controlling HGT may be necessary to maintain the usefulness of antimicrobials.

In-feed antibiotic effects on the swine intestinal microbiome

“…Ten of the 13 phosphotransferases identified in the medicated swine metagenome are homologous (7 of 10 have 100% amino acid identity) with the streptomycin phosphotransferase on the pO86A1 plasmid in E. coli O86:H-(accession number YP_788126). Resistance genes aggregate on plasmids in response to selective pressure (30), and pO86A1 carries at least two other resistance genes (accession number NC_008460). This congregation of resistance genes on mobile genetic elements could offer a fitness advantage to a bacterium living in the constant presence of antibiotics.…”

Whence Resistance?

“…Many of our current antimicrobial agents are actually derived from those naturally produced by non-pathogenic bacteria [3]. These resistance mechanisms are particularly important, in fact essential for self-protection in the very organisms that produce these antimicrobial agents [1].…”

“…These resistance mechanisms are particularly important, in fact essential for self-protection in the very organisms that produce these antimicrobial agents [1]. These resistance mechanisms may ''escape'' and be subsequently ''captured'' by pathogenic bacteria through horizontal gene transfer [1,3].…”

Exploitation of Glycobiology in Anti-Adhesion Approaches against Biothreat Agents

“…The resistance phenomenon in pathogenic organisms has been associated with the overuse and misuse of antibiotics over the last few decades resulting in selective pressure on microbes to adapt and survive the presence of antibiotics. Under such conditions, microbes acquire extra chromosomal elements from other microorganisms in the environment through a process referred to as horizontal gene transfer [2,3]. Similarly, use of strong chemical disinfectants and hygiene products is an additional risk factor, promoting mutations and making eradication procedures inefficient [1].…”