Insights into the antimicrobial effects of tafenoquine against Enterococcus and its biofilms.

Abstract

The purpose of this study is to assess the in vitro antimicrobial and anti-biofilm effects of the anti-protozoal agent tafenoquine (TAF) on Enterococcus and elucidate its underlying mode of action. The present work investigated the susceptibility of TAF on 3 type strains and 11 clinical isolates of enterococci. The results indicated that TAF exhibited powerful antimicrobial activity against both of Enterococcus faecalis and Enterococcus faecium with minimum inhibitory and bactericidal concentrations ranging from 8 to 16µg ml-1. Meanwhile, biofilm inhibition and eradication assays showed that TAF exhibited potent anti-biofilm activity against E. faecalis ATCC 29212 and E. faecium ATCC 19434. Ultra-microscopic observations revealed significant changes in bacterial morphology and structure caused by TAF, particularly for the disruption of plasma membrane. Mechanistic investigations also revealed that TAF altered both membrane permeability and potential while also impacting adenosine triphosphate production as well as reactive oxygen species generation. In addition, no detectable cytotoxicity of TAF on human cells was observed at concentrations near the minimal inhibitory concentration. In summary, this study confirmed that TAF could effectively inhibit Enterococcus as well as its biofilm formation.