Quorum-sensing molecules N-acyl homoserine lactones inhibit Trueperella pyogenes infection in mouse model

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.

A comprehensive analysis of the effect of quorum-sensing molecule 3-oxo-C12-homoserine lactone on Candida auris and Candida albicans

Candida auris occupies similar niches in various infections as Pseudomonas aeruginosa; however, the details of their interspecies communication remain largely unknown. To gain deeper insights into this relationship, phenotypic and transcriptomic analyses were conducted in the presence of the primary P. aeruginosa quorum-sensing molecule, N-(3-oxododecanoyl)-l-homoserine lactone (HSL), against C. auris, with the results compared to those of C. albicans. Our findings indicate that HSL-induced effects are not specific to C. albicans; additionally, several characteristics are present in C. auris but not in C. albicans following HSL exposure. Significant HSL-induced reduction was observed in growth and adhesion of C. auris cells in time -and concentration-dependent way (p < 0.01-0.001). Moreover, HSL reduced intracellular iron and zinc levels (p < 0.05-0.001); furthermore, it modulated C. auris metabolism toward beta-oxidation, which may be associated with the observed reduction in in vivo virulence at lower HSL concentrations compared with C. albicans. RNA-sequencing transcriptome analysis of C. auris revealed 67 and 306 upregulated genes, as well as 111 and 168 downregulated genes, in response to 100 and 200-μM HSL, respectively. We identified 45 overlapping upregulated and 25 overlapping downregulated genes between the two HSL concentrations. Similar to other Candida-derived C12 compounds (e.g., farnesol), HSL reduces several C. auris survival strategies, which may significantly influence the nature of P. aeruginosa-C. auris co-habitation. In conclusion, the obtained findings on C. auris do not provide clear evidence that HSL mediated effects have any favourable consequences in terms of P. aeruginosa-C. auris co-colonisation and/or co-infections.

Furazolidone reduces the pathogenesis of Trueperella pyogenes and Pseudomonas aeruginosa co-infection in a mouse model

The prevalence of abscess disease significantly limits the population expansion of captive forest musk deer, which is an endangered species protected by the legislation of China. Our prior work had demonstrated that Trueperella pyogenes and Pseudomonas aeruginosa are two important microorganisms in causing the abscess disease of forest musk deer, and furazolidone could inhibit the growth and virulence of the pathogens in vitro. In this study, the in vivo protection activity of furazolidone was evaluated by using mouse models chronically infected with T. pyogenes and P. aeruginosa. The results showed that furazolidone treatment significantly increased the survival rates of mice in the co-infection group, all the mice survived at 14 days post-infection. The damage degree of the lung tissues caused by bacterial infection was ameliorated by the treatment of furazolidone from 7 to 14 days post-infection, which also reduced the residual bacterial burden in the lungs. Compared to the untreated control group, the expression levels of genes activated by the quorum-sensing system of P. aeruginosa and the core virulence regulatory genes of T. pyogenes were significantly suppressed by furazolidone. In addition, the results of transcriptomic analyses showed that 270 DEGs were identified in the co-infection group. This finding further revealed that the immune responses of mice could be enhanced by the treatment of furazolidone, and this might also contribute to the clearance of bacteria from the lungs. Therefore, this study clearly reveals the protection activity of furazolidone against P. aeruginosa and T. pyogenes infection, and thus provides a promising candidate in the treatment of abscess disease.

Tyramine, one quorum sensing inhibitor, reduces pathogenicity and restores tetracycline susceptibility in Burkholderia cenocepacia

Burkholderia cenocepacia is an opportunistic respiratory pathogen of particular relevance to patients with cystic fibrosis (CF), primarily regulating its biological functions and virulence factors through two quorum sensing (QS) systems (CepI/R and CciI/R). The highly persistent incidence of multidrug resistant Burkholderia cenocepacia poses a global threat to public health. In this study, we investigated the effects of tyramine, one biogenic amine, on the QS systems of Burkholderia cenocepacia. Genetic and biochemical analyses revealed that tyramine inhibited the production of N-hexanoyl-homoserine (AHL) signaling molecules (C8-HSL and C6-HSL) by blocking the CepI/R and CciI/R systems. As a result, the inhibition of QS systems leads to reduced production of various virulence factors, such as biofilm formation, extracellular polysaccharides, lipase, and swarming motility. Notably, as a potential quorum sensing inhibitor, tyramine exhibits low toxicity in vivo in Galleria mellonella larvae and is well characterized by Lipinski's five rules. It also shows high gastrointestinal absorption and the ability to cross the blood-brain barrier according to SwissADME database and ProTox-II server. Additionally, tyramine was found to enhance the efficacy of tetracycline in reducing the infectivity of Burkholderia cenocepacia in Galleria mellonella larvae infection model. Therefore, tyramine could be a promising candidate for combination therapy with traditional antimicrobials to improve their effectiveness against Burkholderia cenocepacia.

Involvement of the E3 ubiquitin ligase Cblb in host defense and evaluation of transcriptome during Trueperella pyogenes infection

Trueperella pyogenes (T. pyogenes) is a versatile and ingenious bacterium that causes severe suppurative injuries in lots of economically important ruminants. The underlying pathogenesis of T. pyogenes infection remains poorly understood. In the current study, we performed transcriptome sequencing of mouse blood tissue infected with T. pyogenes. A total of 36.73 G clean data were collected, and 136 differentially expressed genes were obtained in the infection group compared to the control group. In addition, we found that the E3 ubiquitin ligase Cblb exhibited significant upregulation in the infection groups compared to the control group. Mechanistically, T. pyogenes infection markedly enhanced the expression of Cblb and regulated the host defense response. Inhibiting Cblb expression with Cblb siRNA impaired the inflammatory response and reduced the effect of phagocytosis in RAW264.7 murine macrophages. Intriguingly, overexpression of Cblb induced a strong inflammatory response and enhanced phagocytosis against T. pyogenes infection in macrophages. More importantly, the overexpression of Cblb significantly reduced the bacterial load and protected mice from the T. pyogenes infections. Therefore, our findings reveal that Cblb is a novel and potential regulator in response to T. pyogenes infection and shed new light on the development of promising treatments against T. pyogenes-related diseases.

Study about the combination strategy of Bacillus subtilis wt55 with AiiO-AIO6 to improve the resistance of zebrafish to Aeromonas veronii infection

Disease problems will seriously restrict the sustainable development of aquaculture, and the environmental-friendly prevention strategies are urgently needed. Probiotics and quorum-quenching enzyme are innovative strategies to control bacterial diseases. Firstly, the bacteriostatic activity of Bacillus subtilis wt55 strain and quenching enzyme AiiO-AIO6 on the growth of Aeromonas veronii were tested in vitro, and the results showed wt55 inhibit the growth of A. veronii, but AiiO-AIO6 did not. Then, the synergistic effects of simple combination of B. subtilis wt55 and AiiO-AIO6 were evaluated next. The results showed this combination could improve the survival rate and significantly reduce the number of invasive A. veronii in gut after challenge compared to the other groups, corresponding to the lower intestinal alkaline phosphatase activity. One of its effect mechanisms is the combination could inhibit the growth of A. veronii in vitro; the other is direct immersion of germ-free zebrafish proved AiiO-AIO6 did not directly regulate the innate immune response of the host, but wt55 did it, and the simple combination group could significantly reduce the expression of nuclear factor kappa-B (NF-κB) and proinflammatory cytokine interleukin-1β (IL-1β), increase the expression of lysozyme gene; and the third is intestinal microbiota also plays a regulatory role: the gut microbiota from combination group could significantly inhibit the expression of IL-1β and NF-κB, and increased the expression of transforming growth factor-β (TGF-β) and lysozyme. Given the effectiveness of this simple combination, a B. subtilis quorum-quenching recombinant expression strain in which AiiO-AIO6 was surface displayed on the spores and secreted by vegetative cells was built. The results showed that the survival rate after challenge was lower than that of the group treated with AiiO-AIO6 or wt55 alone, and the expression of proinflammatory cytokine IL-1β and NF-κB were significantly higher. Our study demonstrated the effectiveness of B. subtilis and AiiO-AIO6 simple combination and established an efficient B. subtilis expression system.

Antibacterial and anti-virulence effects of furazolidone on Trueperella pyogenes and Pseudomonas aeruginosa

Background

Trueperella pyogenes and Pseudomonas aeruginosa are two important bacterial pathogens closely relating to the occurrence and development of forest musk deer respiratory purulent disease. Although T. pyogenes is the causative agent of the disease, the subsequently invaded P. aeruginosa will predominate the infection by producing a substantial amount of quorum-sensing (QS)-controlled virulence factors, and co-infection of them usually creates serious difficulties for veterinary treatment. In order to find a potential compound that targets both T. pyogenes and P. aeruginosa, the antibacterial and anti-virulence capacities of 55 compounds, which have similar core structure to the signal molecules of P. aeruginosa QS system, were tested in this study by performing a series of in vitro screening experiments.

Results

We identified that furazolidone could significantly reduce the cell densities of T. pyogenes in mono-culture or in the co-culture with P. aeruginosa. Although the growth of P. aeruginosa could also be moderately inhibited by furazolidone, the results of phenotypic identification and transcriptomic analysis further revealed that sub-inhibitory furazolidone had remarkable inhibitory effect on the biofilm production, motility, and QS system of P. aeruginosa. Moreover, furazolidone could efficiently protect Caenorhabditis elegans models from P. aeruginosa infection under both fast-killing and slow-killing conditions.

Conclusions

This study reports the antibacterial and anti-virulence abilities of furazolidone on T. pyogenes and P. aeruginosa, and provides a promising strategy and molecular basis for the development of novel anti-infectious drugs to dealing with forest musk deer purulent disease, or other diseases caused by T. pyogenes and P. aeruginosa co-infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03216-5.

Modulation of Gut Microbiota through Dietary Phytochemicals as a Novel Anti-infective Strategy

Quorum Sensing (QS) is a phenomenon in which bacterial cells communicate with each other with the help of several low molecular weight compounds. QS is largely dependent on population density, and it triggers when the concentration of quorum sensing molecules accumulate in the environment and crosses a particular threshold. Once a certain population density is achieved and the concentration of molecules crosses a threshold, the bacterial cells show a collective behavior in response to various chemical stimuli referred to as "auto-inducers". The QS signaling is crucial for several phenotypic characteristics responsible for bacterial survival such as motility, virulence, and biofilm formation. Biofilm formation is also responsible for making bacterial cells resistant to antibiotics. The human gut is home to trillions of bacterial cells collectively called "gut microbiota" or "gut microbes". Gut microbes are a consortium of more than 15,000 bacterial species and play a very crucial role in several body functions such as metabolism, development and maturation of the immune system, and the synthesis of several essential vitamins. Due to its critical role in shaping human survival and its modulating impact on body metabolisms, the gut microbial community has been referred to as "the forgotten organ" by O`Hara et al. (2006) [1]. Several studies have demonstrated that chemical interaction between the members of bacterial cells in the gut is responsible for shaping the overall microbial community. Recent advances in phytochemical research have generated a lot of interest in finding new, effective, and safer alternatives to modern chemical-based medicines. In the context of antimicrobial research various plant extracts have been identified with Quorum Sensing Inhibitory (QSI) activities among bacterial cells. This review focuses on the mechanism of quorum sensing and quorum sensing inhibitors isolated from natural sources.

MicroRNA-302/367 Cluster Impacts Host Antimicrobial Defense via Regulation of Mitophagic Response Against Pseudomonas aeruginosa Infection

Mitophagy has recently been implicated in bacterial infection but the underlying mechanism remains largely unknown. Here, we uncover a role of microRNA-302/367 cluster in regulating mitophagy and its associated host response against bacterial infection. We demonstrate that miR-302/367 cluster expression was significantly increased after Pseudomonas aeruginosa infection. Enhanced expression of miR-302/367 cluster accelerated the mitophagic response in macrophages, thus increasing clearance of invading P. aeruginosa by regulating production of reactive oxygen species (ROS), while application of miR-302/367 cluster inhibitors decreased bacterial clearance. Blocking mitophagy with siRNA against mitophagy receptor prohibitin 2 (PHB2) reduced the effect of miR-302/367 cluster on induction of mitophagy and its-associated P. aeruginosa elimination. In addition, we found that miR-302/367 cluster also increased bacterial clearance in mouse model. Mechanistically, we illustrate that miR-302/367 cluster binds to the 3′-untranslated region of nuclear factor kappa B (NF-κB), a negative regulator of mitophagy, accelerated the process of mitophagy by inhibiting NF-κB. Furthermore, inhibition of NF-κB in macrophages attenuated the ROS or cytokines production and may reduce cell injury by P. aeruginosa infection to maintain cellular homeostasis. Collectively, our findings elucidate that miR-302/367 cluster functions as potent regulators in mitophagy-mediated P. aeruginosa elimination and pinpoint an unexpected functional link between miRNAs and mitophagy.

The Antibacterial Activity and Mechanism of Action of Luteolin Against Trueperella pyogenes

Purpose

This research aimed to investigate the antibacterial activity and potential mechanism of luteolin against T. pyogenes.

Materials and Methods

The broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) of luteolin against various T. pyogenes strains. The potential mechanism of action of luteolin was elucidated through testing and analysing the luteolin-induced alterations of T. pyogenes in several aspects, including cell wall, cell membrane, protein expression, nucleic acid content, topoisomerase activity and energy metabolism.

Results

The MIC values of luteolin against various T. pyogenes isolates and ATCC19411 were 78 µg/mL. The increased cell membrane permeability, destruction of cell wall integrity and TEM images after exposure to luteolin showed that the cell wall and membrane were damaged. The content of total protein and nucleic acid in T. pyogenes decreased significantly after treatment with luteolin (1/2 MIC) for 12, 24, and 36 h. Moreover, a hypochromic effect was observed in the absorption spectrum of luteolin when deoxyribonucleic acid (DNA) was added. In addition, after treatment with luteolin, a decrease in nicked or relaxed DNA content, which was catalysed by T. pyogenes-isolated DNA topoisomerase, was observed. In addition, the adenosine triphosphate (ATP) content in cells and the activity of succinate dehydrogenase (SDH) both decreased when T. pyogenes was exposed to different concentrations (1/4 MIC, 1/2 MIC, 1 MIC, 2 MIC) of luteolin for 1 h.

Conclusion

Luteolin showed distinct antibacterial activity against T. pyogenes by multiple actions, which mainly include destroying the integrity of the cell wall and cell membrane, influencing the expression of proteins, inhibiting nucleic acid synthesis, and interfering with energy metabolism.

The bitterness of genitourinary infections: Properties, ligands of genitourinary bitter taste receptors and mechanisms linking taste sensing to inflammatory processes in the genitourinary tract

BACKGROUND

Though, first identified in the gastrointestinal tract, bitter taste receptors are now believed to be ubiquitously expressed in several regions of the body, including the respiratory tract, where they play a critical role in sensing and clearance of excess metabolic substrates, toxins, debris, and pathogens. More recently, bitter taste receptor expression has been reported in cells, tissues and organs of the genitourinary (GU) system, suggesting that these receptors may play an integral role in mediating inflammatory responses to microbial aggression in the GU tract. However, the mechanisms, linking bitter taste receptor sensing with inflammatory responses are not exactly clear. Here, I review recent data on the properties and ligands of bitter taste receptors and suggest mechanisms of bitter taste receptor signaling in the GU tract, and the molecular pathways that link taste sensing to inflammatory responses in GU tract.

METHOD

Computer-aided search was conducted in Scopus, PubMed, Web of Science and Google Scholar for relevant peer-reviewed articles published between 1990 and 2018, investigating the functional implication of bitter taste receptors in GU infections, using the following keywords: extra-oral bitter taste receptors, bitter taste receptors, GU bitter taste receptors, kidney OR renal OR ureteral OR urethral OR bladder OR detrusor smooth muscle OR testes OR spermatozoa OR prostate OR vaginal OR cervix OR ovarian OR endometrial OR myometrial OR placenta OR cutaneous bitter taste receptors. To identify research gaps on etiopathogenesis of GU infections/inflammation, additional search was conducted using the following keywords: GU inflammatory signaling, GU microbes, GU bacteria, GU virus, GU protozoa, GU microbial metabolites, and GU infection. The retrieved articles were filtered and further screened for relevance according to the aim of the study. A narrative review was performed for selected literatures.

RESULTS

Bitter taste receptors of the GU tract may constitute essential components of the pathogenetic mechanisms of GU infections/inflammation that are activated by microbial components, known as quorum sensing signal molecules. Based on accumulating evidences, indicating that taste receptors may signal downstream to activate inflammatory cascades, in addition to the nitric oxide-induced microbicidal effects produced upon taste receptor activation, it is suggested that the anti-inflammatory activities of bitter taste receptor stimulation are mediated via pathways involving the nuclear factor κB by downstream signaling of the metabolic and stress sensors, adenosine monophosphate-activated protein kinase and nicotinamide adenine dinucleotide-dependent silent mating type information regulation 2 homolog 1 (sirtuin 1), resulting to the synthesis of anti-inflammatory cytokines/chemokines, and antimicrobial factors, which ultimately, under normal conditions, leads to the elimination of microbial aggression.

CONCLUSIONS

GU bitter taste receptors may represent critical players in GU tract infections/inflammation. Bitter taste receptors may serve as important therapeutic target for treatment of a number of infectious diseases that affect the GU tract.

Challenges and Limitations of Anti-quorum Sensing Therapies

Quorum sensing (QS) is a mechanism allowing microorganisms to sense population density and synchronously control genes expression. It has been shown that QS supervises the activity of many processes important for microbial pathogenicity, e.g., sporulation, biofilm formation, and secretion of enzymes or membrane vesicles. This contributed to the concept of anti-QS therapy [also called quorum quenching (QQ)] and the opportunity of its application in fighting against various types of pathogens. In recent years, many published articles reported promising results indicating the possibility of reducing pathogenicity of tested microorganisms and their easier eradication when co-treated with antibiotics. The aim of the present article is to point to the opposite, negative side of the QQ therapy, with particular emphasis on three fundamental properties attributed to anti-QS substances: the selectivity, virulence reduction, and lack of resistance against QQ. This point of view may highlight new directions of research, which should be taken into account in the future before the widespread introduction of QQ therapies in the treatment of people.

MTOR involved in bacterial elimination against Trueperella pyogenes infection based on mice model by transcriptome and biochemical analysis

Trueperella pyogenes is an importantly opportunistic and commensal pathogen that causes suppurative lesions of most economically important livestock. To understand the molecular mechanism underlying the infection by T. pyogenes, we carried out a large-scale transcriptome sequencing of mice livers intraperitoneally infected with T. pyogenes using RNA-sequencing. A total of 47 G clean bases were obtained and 136 differentially expressed genes were detected between the control and the infection groups in the liver transcriptomes. Additionally, we found that the expression of a key autophagy regulator, mTOR (mechanistic target of rapamycin) was significantly up-regulated in the infection groups. Mechanistically, T. pyogenes infection induced the expression of mTOR and subsequently inhibited the autophagy of host cell. Blocking autophagy with inhibitor 3-methyladenine (3-MA) or silencing autophagy-related gene 7 (Atg7) reduced the effect of bacterial elimination. Interestingly, inhibition of mTOR induced autophagy and reduced T. pyogenes viability in RAW264.7 murine macrophages. The silencing mTOR regulated oxidation and cytokines (interleukin-1β, IL-6 and tumor necrosis factro-α) against T. pyogenes in macrophages and significantly protected mice from T. pyogenes challenge. These findings indicate that mTOR is a novel functional regulator in autophagy-mediated T. pyogenes elimination and will be useful to further knowledge on the development of effective therapeutic strategy to control T. pyogenes-related diseases.

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.

Population divergence of Pseudomonas aeruginosa can lead to the coexistence with Escherichia coli in animal suppurative lesions

Purulent disease is the main factor that prevents the population increase of forest musk deer in artificial breeding, and especially the intracorporal suppurative lesions in late-stage with complex bacterial communities normally bring more difficulties for veterinary treatment. Although it is well-recognized that Pseudomonas aeruginosa and Escherichia coli are the two main bacterial pathogens which can be frequently co-isolated from the lung pus of forest musk deer, few studies have explored the interspecific relationship and coexistent mechanism of the two species. In this study, we identified a P. aeruginosa strain MYL-2, which harbored a loss-of-function mutation in the central regulator (LasR) of quorum-sensing (QS) system, from the lung pus of a dying forest musk deer with co-infecting E. coli strain MYL-58. Interestingly, P. aeruginosa MYL-2 could coexist with E. coli MYL-58 compared to the dominant role of lasR-intact P. aeruginosa strain MYL-1 in the competitive experiments. The results of in vitro coevolution assay further revealed that the QS-mediated competitive advantage of P. aeruginosa MYL-1 would be decreased along with the enrichment of lasR mutants in the communities, and P. aeruginosa could finally coexist with E. coli by forming a relatively stable equilibrium. Therefore, these findings provide an evolutionary explanation for the coexistence of P. aeruginosa and E. coli in the suppurative lesions of forest musk deer, and may also contribute to further understanding the pathology of animal purulent disease and the development of novel veterinary therapy.

Determination of the expression of three fimbrial subunit proteins in cultured Trueperella pyogenes

Background

Trueperella pyogenes is a commensal and a significant opportunistic pathogen in animals. A variety of identified or putative virulence factors are considered to significantly contribute to the occurrence of T. pyogenes infection in different species. However, these virulence factors are not fully understood.

Results

In the current study, the genes encoding putative fimbrial proteins, i.e. Fim A, Fim C, and Fim E, were cloned. Recombinant Fim A (rFim A), Fim C (rFim C), and Fim E (rFim E) were prepared and used to generate rabbit anti-rFim A, anti-rFim C, and anti-rFim E serum, respectively. Using these sera, we found that only Fim E was constitutively expressed in T. pyogenes. The expression level of Fim E in T. pyogenes peaked within 6–10 h of culture period in pH 7.5. Fim E protein expression was unaffected by anaerobic condition, but was inhibited by the microaerophilic condition. Tube agglutination tests indicated that Fim E was exhibited on the surface of T. pyogenes cells because anti-rFim E serum caused strong agglutination. Additionally, the blots for Fim A detection showed nonspecific reactions. Furthermore, the tube agglutination tests showed that anti-Fim A serum failed to cause agglutination of T. pyogenes cells, which indicated that Fim A was not, or poorly, expressed in cultured T. pyogenes. Anti-rFim C serum caused strong agglutination. However, the blots for Fim C detection showed a strong nonspecific reaction. Thus, the expression of Fim C was difficult to be determined using the current method.

Conclusions

Fim E was expressed in cultured T. pyogenes. However, Fim A was either not or poorly expressed in cultured T. pyogenes. Moreover, Fim C expression was not determined using the current strategy.

Electronic supplementary material

The online version of this article (10.1186/s13028-018-0407-3) contains supplementary material, which is available to authorized users.