Identification of B-cell linear epitopes in domains 1-3 of pyolysin of Trueperella pyogenes using polyclonal antibodies

Luteolin increases susceptibility to macrolides by inhibiting MsrA efflux pump in Trueperella pyogenes

Trueperella pyogenes (T. pyogenes) is an opportunistic pathogen associated with a variety of diseases in many domestic animals. Therapeutic treatment options for T. pyogenes infections are becoming limited due to antimicrobial resistance, in which efflux pumps play an important role. This study aims to evaluate the inhibitory activity of luteolin, a natural flavonoid, on the MsrA efflux pump and investigate its mechanism. The results of antimicrobial susceptibility testing indicated that the susceptibility of msrA-positive T. pyogenes isolates to six macrolides increased after luteolin treatment, while the susceptibility of msrA-negative isolates showed no change after luteolin treatment. It is suspected that luteolin may increase the susceptibility of T. pyogenes isolates by inhibiting MsrA activity. After 1/2 MIC luteolin treatment for 36 h, the transcription level of the msrA gene and the expression level of the MsrA protein decreased by 55.0-97.7% and 36.5-71.5%, respectively. The results of an affinity test showed that the equilibrium dissociation constant (KD) of luteolin and MsrA was 6.462 × 10-5 M, and hydrogen bonding was predominant in the interaction of luteolin and MsrA. Luteolin may inhibit the ATPase activity of the MsrA protein, resulting in its lack of an energy source. The current study illustrates the effect of luteolin on MsrA in T. pyogenes isolates and provides insight into the development of luteolin as an innovative agent in combating infections caused by antimicrobial-resistant bacteria.

New Determinants of Aminoglycoside Resistance and Their Association with the Class 1 Integron Gene Cassettes in Trueperella pyogenes

Trueperella pyogenes is an important opportunistic animal pathogen. Different antimicrobials, including aminoglycosides, are used to treat T. pyogenes infections. The aim of the present study was to evaluate aminoglycoside susceptibility and to detect aminoglycoside resistance determinants in 86 T. pyogenes isolates of different origin. Minimum inhibitory concentration of gentamicin, streptomycin, and kanamycin was determined using a standard broth microdilution method. Genetic elements associated with aminoglycoside resistance were investigated by PCR and DNA sequencing. All studied isolates were susceptible to gentamicin, but 32.6% and 11.6% of them were classified as resistant to streptomycin and kanamycin, respectively. A total of 30 (34.9%) isolates contained class 1 integrons. Class 1 integron gene cassettes carrying aminoglycoside resistance genes, aadA11 and aadA9, were found in seven and two isolates, respectively. Additionally, the aadA9 gene found in six isolates was not associated with mobile genetic elements. Moreover, other, not carried by gene cassettes, aminoglycoside resistance genes, strA-strB and aph(3’)-IIIa, were also detected. Most importantly, this is the first description of all reported genes in T. pyogenes. Nevertheless, the relevance of the resistance phenotype to genotype was not perfectly matched in 14 isolates. Therefore, further investigations are needed to fully explain aminoglycoside resistance mechanisms in T. pyogenes.

Evaluation of the Potency of Two Pyolysin-Derived Recombinant Proteins as Vaccine Candidates of Trueperella Pyogenes in a Mouse Model: Pyolysin Oligomerization and Structural Change Affect the Efficacy of Pyolysin-Based Vaccines

Trueperella pyogenes (T. pyogenes) is an important opportunistic pathogen in livestock and wild animals. However, only one commercial T. pyogenes vaccine is currently available, and its immunoprotective effect is not ideal. Pyolysin (PLO) is one of the important virulence factors expressed by T. pyogenes and one of the targets for the development of new T. pyogenes vaccines. In this study, we constructed two recombinant antigens, tPLOA1 (contains amino acids 1–110 and domain 4 of the PLO molecule) and tPLOA2 (contains amino acids 190–296 and domain 4 of the PLO molecule). Vaccines were prepared by mixing the two recombinant antigens with incomplete Freund’s adjuvant or sheep red blood cell membrane and provided partial immune protection to immunized mice against the lethal challenge of T. pyogenes. Analysis of the PLO-specific IgG levels of immunized mice indicated that the antibody-inducing potency and immunoprotective efficacy of PLO-based vaccines are affected by the oligomerization and structural changes of PLO after binding to a cholesterol-containing membrane. In addition, the titer of anti-hemolysis antibodies is not a suitable indicator of the immunoprotective effect of these vaccines in PLO-based vaccine-immunized animals. The results provide new insights into the development of T. pyogenes vaccines.

Pathogenicity and Virulence of Trueperella pyogenes: A Review

Bacteria from the species Trueperella pyogenes are a part of the biota of skin and mucous membranes of the upper respiratory, gastrointestinal, or urogenital tracts of animals, but also, opportunistic pathogens. T. pyogenes causes a variety of purulent infections, such as metritis, mastitis, pneumonia, and abscesses, which, in livestock breeding, generate significant economic losses. Although this species has been known for a long time, many questions concerning the mechanisms of infection pathogenesis, as well as reservoirs and routes of transmission of bacteria, remain poorly understood. Pyolysin is a major known virulence factor of T. pyogenes that belongs to the family of cholesterol-dependent cytolysins. Its cytolytic activity is associated with transmembrane pore formation. Other putative virulence factors, including neuraminidases, extracellular matrix-binding proteins, fimbriae, and biofilm formation ability, contribute to the adhesion and colonization of the host tissues. However, data about the pathogen–host interactions that may be involved in the development of T. pyogenes infection are still limited. The aim of this review is to present the current knowledge about the pathogenic potential and virulence of T. pyogenes.

Antimicrobial resistance and presence of virulence factor genes in Trueperella pyogenes isolated from pig lungs with pneumonia

Trueperella pyogenes (T. pyogenes) is a worldwide known pathogen of domestic ruminants and pigs causing a wide variety of infections. The objective of this study was to report the presence of major virulence genes in T. pyogenes isolated from pigs with respiratory clinical signs and determine their resistance to antibiotics at the same time. A total of 27 T. pyogenes strains were obtained from Jilin Province, and the nanH, nanP, cbpA, fimC, and fimE virulence genes were detected in 7 (25.9%), 14 (51.9%), 18 (66.7%), 8 (29.6%), and 16 (59.3%) isolates, respectively. All isolates were observed to harbor plo and fimA genes. However, 27 T. pyogenes strains tested negative for fimG gene. Antibiotic susceptibility tests revealed that the isolated strains had extensive drug resistance, all isolates were sensitive to fluoroquinolones and penicillins antibiotics, and high levels of resistance were found to gentamicin (77.8%), amikacin (74.1%), erythromycin (85.2%), and azithromycin (85.2%). These results highlights the need for prudent use of specific antimicrobial agents in veterinary clinical treatment.

Replacing the 238th aspartic acid with an arginine impaired the oligomerization activity and inflammation-inducing property of pyolysin

Trueperella pyogenes (T. pyogenes) is an important opportunistic pathogen. Pyolysin (PLO) importantly contributes to the pathogenicity of T. pyogenes. However, the relationship between the structure and function and the virulence of PLO is not well documented. In the current study, recombinant PLO (rPLO) and three rPLO mutants were prepared. rPLO D238R, a mutant with the 238th aspartic acid replaced with an arginine, showed impairment in oligomerization activity on cholesterol-containing liposome and pore-forming activity on sheep red blood cell membrane. Further study employing the prepared mutants confirmed that the pore-forming activity of PLO is essential for inducing excessive inflammation responses in mice by upregulating the expression levels of IL-1β, TNF-α, and IL-6. By contrast, rPLO P499F, another mutant with impaired cell membrane binding capacity, elicited an inflammation response that was dependent on pathogen-associated molecular pattern (PAMP) activity, given that the mutant significantly upregulated the expression of IL-10 in macrophages and in mice, whereas rPLO did not. Results indicated that domain 1 of the PLO molecule plays an important role in maintaining pore-forming activity. Moreover, the PLO pore-forming activity and not PAMP activity is responsible for the inflammation-inducing effect of PLO. The results of this study provided new information for research field on the structure, function, and virulence of PLO.

Abbreviations: T. pyogenes: Trueperella pyogenes; PLO: Pyolysin; rPLO: recombinant PLO; PAMP: pathogen-associated molecular pattern; CDCs: cholesterol-dependent cytolysins; PLY: pneumolysin; NLRP3: NLR family pyrin domain containing protein 3; PRRs: pattern recognition receptors; Asp: aspartic acid; TLR4: Toll-like receptor 4; Arg: arginine; Asn: asparagine; IPTG: Isopropyl-β-d-thiogalactoside; PBS: phosphate-buffered saline; sRBCs: sheep red blood cells; TEM: Transmission electron microscopy; RBCM: red blood cell membrane; SDS-PAGE: sodium dodecyl sulfate–polyacrylamide gel electrophoresis; NC membrane: nitrocellulose membrane; SDS-AGE: dodecyl sulfate agarose gel electrophoresis; MDBK cells: Madin–Darby bovine kidney cells; RPMI-1640 medium: Roswell Park Memorial Institute-1640 medium; FBS: fetal bovine serum; BMDMs: bone marrow-derived macrophages; TNF-α: tumor necrosis factor α; IL-1β: interleukin-1β; IFN-γ: interferon-γ; TGF-β: transforming growth factor-β; ELISA: enzyme-linked immunosorbent assay