The gene encoding pyolysin, the pore-forming toxin of Arcanobacterium pyogenes, resides within a genomic islet flanked by essential genes

Virulence factors and therapeutic methods of Trueperella pyogenes: A review

Trueperella pyogenes is a prevalent opportunistic pathogen responsible for a wide range of infections in livestock and wildlife, such as in cattle, pigs, European bison and forest musk deer. Much of the successful infection of T. pyogenes relies on its virulence factors, including pyolysin as well as adhesion factors. The swift rise of bacterial resistance has highlighted the urgent need for developing new therapeutic strategies. Currently, virulence factor-mediated vaccine development and other therapeutic approaches are widely regarded as the primary interventions for addressing diseases associated with this pathogen. This review examines the broader virulence potential of T. pyogenes, focusing on haemolysin, host cell adhesion proteins, the prevalence of antibiotic resistance, and the development of vaccines mediated by virulence factors. Additionally, it discusses current and future approaches aimed at improving therapeutic interventions.

Revealing the Mechanism of NLRP3 Inflammatory Pathway Activation through K+ Efflux Induced by PLO via Signal Point Mutations

Trueperella pyogenes is an important opportunistic pathogenic bacterium widely distributed in the environment. Pyolysin (PLO) is a primary virulence factor of T. pyogenes and capable of lysing many different cells. PLO is a member of the cholesterol-dependent cytolysin (CDC) family of which the primary structure only presents a low level of homology with other members from 31% to 45%. By deeply studying PLO, we can understand the overall pathogenic mechanism of CDC family proteins. This study established a mouse muscle tissue model infected with recombinant PLO (rPLO) and its single-point mutations, rPLO N139K and rPLO F240A, and explored its mechanism of causing inflammatory damage. The inflammatory injury abilities of rPLO N139K and rPLO F240A are significantly reduced compared to rPLO. This study elaborated on the inflammatory mechanism of PLO by examining its unit point mutations in detail. Our data also provide a theoretical basis and practical significance for future research on toxins and bacteria.

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.

A chimeric protein composed of the binding domains of Clostridium perfringens phospholipase C and Trueperella pyogenes pyolysin induces partial immunoprotection in a mouse model

Trueperella pyogenes and Clostridium perfringens are two kinds of conditional pathogens frequently associated with wound infections and succeeding lethal complications in various economic livestock. Pyolysin (PLO) and phospholipase C (PLC) are the key virulence factors of these two pathogens, respectively. In our study, a chimeric protein called rPC-PD4, which is composed of the binding regions of PLO and PLC, was synthesized. The toxicity of rPC-PD4 was evaluated. Results revealed that rPC-PD4 is a safe chimeric molecule that can be used to develop vaccines. Immunizing BALB/c mice with rPC-PD4 induced high titers of serum antibodies that could efficiently neutralize the hemolytic activity of recombinant PLO and PLC. After the challenge with T. pyogenes or C. perfringens was performed through the intraperitoneal route, we observed that rPC-PD4 immunization could provide partial immunoprotection and reduce lung, intestine, and liver tissue damage to mice. This work demonstrated the efficacy of the rationally designed rPC-PD4 chimeric protein as a potential vaccine candidate against C. perfringens and T. pyogenes.

In vitro and in vivo expression of virulence genes in Trueperella pyogenes based on a mouse model

Trueperella pyogenes is an important opportunistic pathogen causing a number of pyogenic infections in ruminants and other animals. This microorganism expresses several extracellular virulence proteins that contribute to its pathogenic potential. To investigate the expression levels of haemolytic exotoxin pyolysin, neuraminidases, collagen-binding protein and fimbriae of T. pyogenes in routine culture and infection process, 10 T. pyogenes isolates which simultaneously harbored ftsY, plo, cbpA, fimA, fimC, nanP, and nanH genes were injected into 10/group Kunming (KM) mice to determine their virulence. In vitro expressions of these genes were determined by quantitative PCR. Subsequently, three typical isolates including an avirulent, a moderately virulent and a strongly virulent isolate were respectively injected into mouse model to determine the in vivo expression of these genes. Finally, significant correlation was observed between collagen-binding protein, neuraminidases, and fimbriae. The expression level of pyolysin was negatively correlated with the survival of injected mice. The time course of virulence gene expression was monitored based on the expression of virulence genes in mouse model. In conclusion, the in vitro and in vivo gene expression study showed a clear difference in virulence gene expression between virulent and non-virulent isolates.

Arcanolysin is a cholesterol-dependent cytolysin of the human pathogen Arcanobacterium haemolyticum

Background

Arcanobacterium haemolyticum is an emerging human pathogen that causes pharyngitis, wound infections, and a variety of occasional invasive diseases. Since its initial discovery in 1946, this Gram positive organism has been known to have hemolytic activity, yet no hemolysin has been previously reported. A. haemolyticum also displays variable hemolytic activity on laboratory blood agar that is dependent upon which species the blood is derived.

Results

Here we describe a cholesterol-dependent cytolysin (CDC) secreted by A. haemolyticum, designated arcanolysin (aln), which is present in all strains (n = 52) tested by DNA dot hybridization. Among the known CDCs, ALN is most closely related to pyolysin (PLO) from Trueperella (formerly Arcanobacterium) pyogenes. The aln probe, however, did not hybridize to DNA from T. pyogenes. The aln open reading frame has a lower mol %G+C (46.7%) than the rest of the A. haemolyticum genome (53.1%) and is flanked by two tRNA genes, consistent with probable acquisition by horizontal transfer. The ALN protein (~ 64 kDa) contains a predicted signal sequence, a putative PEST sequence, and a variant undecapeptide within domain 4, which is typically important for function of the toxins. The gene encoding ALN was cloned and expressed in Escherichia coli as a functional recombinant toxin. Recombinant ALN had hemolytic activity on erythrocytes and cytolytic activity on cultured cells from human, rabbit, pig and horse origins but was poorly active on ovine, bovine, murine, and canine cells. ALN was less sensitive to inhibition by free cholesterol than perfringolysin O, consistent with the presence of the variant undecapeptide.

Conclusions

ALN is a newly identified CDC with hemolytic activity and unique properties in the CDC family and may be a virulence determinant for A. haemolyticum.

Transcriptional regulation of pyolysin production in the animal pathogen, Arcanobacterium pyogenes

Arcanobacterium pyogenes is an opportunistic pathogen of a number of important livestock species, and usually infects from an endogenous, commensal source. Thus, as with other normal flora opportunistic pathogens, the regulation of A. pyogenes virulence factors is likely important during both commensal and pathogenic interactions with the host. The aim of this study was to investigate the regulation of a key A. pyogenes virulence factor, the cholesterol dependent cytolysin, pyolysin (PLO), under in vitro conditions, as a first step to understanding its regulation during the disease process. Analysis of PLO production in broth culture indicated that expression of PLO was induced during early stationary phase, and that this correlated with an increase in plo-specific mRNA. Analysis of a plo-cat transcriptional fusion indicated that transcription of plo was also induced during early stationary phase. Primer extension analysis and 5' RACE suggested that two putative promoter sequences, P1 and P2 were active. Analysis of site-directed mutants of these promoters in the plo-cat fusion indicated that P2 was the major stationary phase promoter. Deletions of the plo promoter region from the plo-cat fusion implicated three direct repeat (DR) sequences as important for plo transcription. Mutagenesis of both DR1 and DR2 resulted in reduction in plo transcription, while the presence of only DR3 in deletions of the plo promoter region repressed transcription from P2. Gel shift experiments indicated that a soluble factor from A. pyogenes binds to the plo promoter region and that the DRs may act as binding sites for a transcriptional regulator.

Multiple genetic elements carry the tetracycline resistance gene tet(W) in the animal pathogen Arcanobacterium pyogenes

The tet(W) gene is associated with tetracycline resistance in a wide range of bacterial species, including obligately anaerobic rumen bacteria and isolates from the human gut and oral mucosa. However, little is known about how this gene is disseminated and the types of genetic elements it is carried on. We examined tetracycline-resistant isolates of the animal commensal and opportunistic pathogen Arcanobacterium pyogenes, all of which carried tet(W), and identified three genetic elements designated ATE-1, ATE-2, and ATE-3. These elements were found in 25%, 35%, and 60% of tetracycline-resistant isolates, respectively, with some strains carrying both ATE-2 and ATE-3. ATE-1 shows characteristics of a mobilizable transposon, and the tet(W) genes from strains carrying this element can be transferred at low frequencies between A. pyogenes strains. ATE-2 has characteristics of a simple transposon, carrying only the resistance gene and a transposase, while in ATE-3, the tet(W) gene is associated with a streptomycin resistance gene that is 100% identical at the DNA level with the aadE gene from the Campylobacter jejuni plasmid pCG8245. Both ATE-2 and ATE-3 show evidence of being carried on larger genetic elements, but conjugation to other strains was not observed under the conditions tested. ATE-1 was preferentially associated with A. pyogenes strains of bovine origin, while ATE-2 and ATE-3 elements were primarily found in porcine isolates, suggesting that these elements may circulate in different environments. In addition, four alleles of the tet(W) gene, primarily associated with different elements, were detected among A. pyogenes isolates.

Arcanobacterium pyogenes: molecular pathogenesis of an animal opportunist

Arcanobacterium pyogenes is a commensal and an opportunistic pathogen of economically important livestock, causing diseases as diverse as mastitis, liver abscessation and pneumonia. This organism possesses a number of virulence factors that contribute to its pathogenic potential. A. pyogenes expresses a cholesterol-dependent cytolysin, pyolysin, which is a haemolysin and is cytolytic for immune cells, including macrophages. Expression of pyolysin is required for virulence and this molecule is the most promising vaccine candidate identified to date. A. pyogenes also possesses a number of adherence mechanisms, including two neuraminidases, the action of which are required for full adhesion to epithelial cells, and several extracellular matrix-binding proteins, including a collagen-binding protein, which may be required for adhesion to collagen-rich tissue. A. pyogenes also expresses fimbriae, which are similar to the type 2 fimbriae of Actinomyces naeslundii, and forms biofilms. However, the role of these factors in the pathogenesis of A. pyogenes infections remains to be elucidated. A. pyogenes also invades and survives within epithelial cells and can survive within J774A.1 macrophages for up to 72 h, suggesting an important role for A. pyogenes interaction with host cells during pathogenesis. The two component regulatory system, PloSR, up-regulates pyolysin expression and biofilm formation but down-regulates expression of proteases, suggesting that it may act as a global regulator of A. pyogenes virulence. A. pyogenes is a versatile pathogen, with an arsenal of virulence determinants. However, most aspects of the pathogenesis of infection caused by this important opportunistic pathogen remain poorly characterized.