Effect Of Traditional Antimicrobials And Novel Antimicrobials On Bacterial Growth And Bacterial Resistance

With the overuse and even abuse of antibacterial agents,many drug-resistant bacteria have appeared in clinic and environment.However,research of the bacterial growth and production and spread of antibiotic resistance genes(ARG)were limited when the bacterial were exposed to new antimicrobials or the mixtures of traditional antimicrobials and new antimicrobials.Therefore,in this paper,we choosed A.fischeri,E.coli and B.subtilis as model organisms,silver antimicrobials,polypeptides and QSIs were selected as test compounds.In view of the influence of bacterial growth and ARG when exposed to the single new antimicrobials and mixtures of traditional antibacterial agents and new antibacterial agents,we studied the effects on bacterial growth and on the generation and horizontal transfer of resistance genes when the bacterial were exposed to the single new antibacterials and the mixtures of silver antimicrobials-QSIs and silver antimicrobials-polypeptides.The results showed that all silver antimicrobials and QSIs inhibited the three bacteria,while only five peptide antibiotics have toxic effects on all three bacteria and the maximum inhibition rate can reach 50%.The three antibacterial agents promoted the junction transfer of RP4 plasmid,and the dose-effect curve shows an inverted "U" shape.The joint effects of silver antimicrobials-QSIs against gram-negative bacteria were additive or antagonistic,while were mostly synergistic for the positive bacteria.And silver antimicrobials-QSIs mixture were antagonistic for the RP4 plasmid and the mutation of E.coli.In the study of the silver antimicrobials-polypeptides mixtures,it was found that the silver antibacterial antimicrobials-bacillus and the silver antimicrobials-polymyxin B could exhibit synergistic effect on the growth of gram-negative bacteria and produce synergistic effect while others were synergistic or additive.The silver antimicrobials-polypeptides mixtures were able to promote the junctional transfer of the RP4 plasmid and mutational effects.This paper provides a new idea for the study of bacterial resistance mechanisms from the perspective of mixed antibacterial agent and give references and supports for the ecological risk assessment of mixed antibacterial agents.