Targeted allele replacement mutagenesis of Corynebacterium pseudotuberculosis

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

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.

Differential endometrial cell sensitivity to a cholesterol-dependent cytolysin links Trueperella pyogenes to uterine disease in cattle

Purulent disease of the uterus develops in 40% of dairy cows after parturition, when the epithelium of the endometrium is disrupted to expose the underlying stroma to bacteria. The severity of endometrial pathology is associated with isolation of Trueperella pyogenes. In the present study, T. pyogenes alone caused uterine disease when infused into the uterus of cattle where the endometrial epithelium was disrupted. The bacterium secretes a cholesterol-dependent cytolysin, pyolysin (PLO), and the plo gene was identical and the plo gene promoter was highly similar amongst 12 clinical isolates of T. pyogenes. Bacteria-free filtrates of the T. pyogenes cultures caused hemolysis and endometrial cytolysis, and PLO was the main cytolytic agent, because addition of anti-PLO antibody prevented cytolysis. Similarly, a plo-deletion T. pyogenes mutant did not cause hemolysis or endometrial cytolysis. Endometrial stromal cells were notably more sensitive to PLO-mediated cytolysis than epithelial or immune cells. Stromal cells also contained more cholesterol than epithelial cells, and reducing stromal cell cholesterol content using cyclodextrins protected against PLO. Although T. pyogenes or plo-deletion T. pyogenes stimulated accumulation of inflammatory mediators, such as IL-1beta, IL-6, and IL-8, from endometrium, PLO did not stimulate inflammatory responses by endometrial or hematopoietic cells, or in vitro organ cultures of endometrium. The marked sensitivity of stromal cells to PLO-mediated cytolysis provides an explanation for how T. pyogenes acts as an opportunistic pathogen to cause pathology of the endometrium once the protective epithelium is lost after parturition.