Fitness costs of plasmids carrying antibiotic resistance genes

<p indent="0mm">Antibiotic resistance is linked to bacterial adaptability. Aside from that, antibiotic resistance genes (ARGs) carried by plasmids contribute tremendously to the global spread of antibiotic resistance. Nevertheless, while ARG plasmids facilitate the adaptation of host bacteria to various environments, they also impose a fitness cost on host bacteria. Under antibiotic selection pressure, ARG plasmids are advantageous to host bacteria as they increase their survival rate in the presence of antibiotics. In contrast, in the absence of antibiotic selection pressure, ARG plasmids cause fitness costs to the bacterial host. The fitness costs include growth-survival effects (lowered growth rate and viability), vertical-horizontal transfer effects (changes in the transfer mode and inhibition of ARGs plasmid transfer), and bacterial virulence effects (low host invasiveness and toxin secretion). Under such circumstances, this can not only lower the competitiveness and narrow the ecological niches of the host bacteria but can also eliminate them from the bacterial populations. Host bacteria can lessen fitness costs through several mechanisms (mutation-compensating evolution, nonmutational compensation, and conjugation transfer), which can help retain them in the population. Notably, the various reduction mechanisms of ARG plasmid fitness cost have impeded or even halted the reversal of bacterial resistance by controlling antibiotic misuse. Therefore, it is imperative to conduct research into mechanisms by which fitness cost reduction pathways can be blocked, and antibiotic susceptibility in bacteria with ARGs plasmids can be restored. This can limit the spread of antibiotic resistance. Additionally, it is essential to conduct experiments under a wide range of real-world environmental conditions. This will help to develop a novel approach for effectively addressing the antibiotic resistance crisis and the establishment of an all-around risk assessment system.