The dominance of bacterial genotypes leads to susceptibility variations under sublethal antibiotic pressure

To investigate the collective resistance of the bacteria population with resistant horizontal gene transfer under sublethal bactericide pressure.

By employing qualitative analysis of ordinary differential equations, particularly bifurcation theory and several numerical simulations, a modified 4D ordinary differential equation model describing antibiotic susceptibility variations induced by sublethal antibiotic pressure is analyzed in detail.

The long-term behaviors and collective resistance of different bacterial genotype populations in different sublethal bactericide concentration subintervals exhibit high levels of heterogeneity and are determined by the protection provided by resistant genes on chromosome or plasmid, their fitness costs, plasmid segregation rate and sublethal bactericide pressure.

First, the possible mechanism of antibiotic susceptibility variations is the dominance of different bacterial genotypes under sublethal bactericide pressure, rather than persistence, tolerance or resistance. Additionally, the combination of vertical genetic transfer, horizontal genetic transfer and plasmid segregation can lead to unique switch between two states of different bacterial genotypes.