Luteolin Showed a Resistance Elimination Effect on Gentamicin by Decreasing MATE mRNA Expression in Trueperella...

Trueperella pyogenes is a common inhabitant of mucosal surfaces in animals and causes a variety of infections, including endometritis, mastitis, and liver abscessation, in dairy cows. Many antimicrobial agents are used for treatment of infections caused by T. pyogenes; however, antibiotic resistance has recently become a serious problem. The objective of this study was to characterize the effect of the efflux pump-encoding multidrug and toxic compound extrusion (MATE) gene on antibiotic resistance in T. pyogenes isolates from cows with signs of endometritis. As a compound from plants, luteolin showed antimicrobial activities in Escherichia coli and Staphylococcus aureus; therefore, we also investigated whether luteolin can eliminate antibiotic resistance. We constructed a MATE deletion mutant in BM-H06-3 to identify the function of MATE in antibiotic resistance. MATE mRNA expression was measured to identify the mechanism of luteolin in gentamicin resistance elimination effect in T. pyogenes. The T. pyogenes isolate BM-H06-3 became susceptible to gentamicin, amikacin, streptomycin, erythromycin, and roxithromycin after MATE deletion. No synergistic effect between luteolin and gentamicin was observed in eight isolates, which were randomly selected from 34 T. pyogenes isolates, but the isolates became susceptible to gentamicin after luteolin treatment at a subinhibitory concentration (1/4 minimum inhibitory concentration [MIC]) for 36 hr. Furthermore, luteolin can decrease MATE mRNA expression after luteolin treatment at a subinhibitory concentration (1/4 MIC). We found that the MATE gene was involved in antibiotic resistance and that luteolin induces a resistance elimination effect in T. pyogenes. Therefore, luteolin may be a potential agent to inhibit efflux pumps in multidrug-resistant T. pyogenes.