The Vibrio parahaemolyticus Type III Secretion Systems manipulate host cell MAPK for critical steps in pathogenesis

Vibrio harveyi uses both type III secretion system and quorum sensing for the colonization of the European abalone

The vibriosis of the European abalone, Haliotis tuberculata, is characterized by the rapidity of the infection by the pathogen Vibrio harveyi ORM4, leading to death of animals only after two days. The lethality of the pathogen is linked to the production of the type III secretion system (T3SS) and to genes regulated by quorum sensing (QS). The aim of this study was to investigate the colonization of the European abalone by both virulent and avirulent V. harveyi strains, as well as the involvement of T3SS and QS during infection. Our results emphasize the importance of gills for the bacterial establishment as the bacterial concentration of the avirulent V. harveyi strain significantly decreased from 189.3 ± 98.6 CFU/mg to 0.8 ± 0.5 CFU/mg between 24 and 48 h post-infection (hpi). In opposition, the pathogen V. harveyi ORM4 was able to maintain itself on the gills, with a concentration of 461.9 ± CFU/mg at 48 hpi, which was allowed by the production of T3SS and a functional QS. Following the infection cycle of V. harveyi ORM4 inside H. tuberculata, we also demonstrated that QS is essential for the ability of V. harveyi ORM4 to colonize the abalone hemolymph and to maintain in it. In response to the presence of V. harveyi, an increase in reactive oxygen species production was recorded, while the phagocytosis activity remained unchanged. We also highlighted the involvement of both QS and T3SS to escape the immune system activity, and that an overproduction of T3SS induced hemocyte mortality. This study provides the evidence that both T3SS and QS are essential for the establishment of V. harveyi ORM4 inside the European abalone.

Contribution of the Type III Secretion System (T3SS2) of Vibrio parahaemolyticus in Mitochondrial Stress in Human Intestinal Cells

Vibrio parahaemolyticus is an important human pathogen that is currently the leading cause of shellfish-borne gastroenteritis in the world. Particularly, the pandemic strain has the capacity to induce cytotoxicity and enterotoxicity through its Type 3 Secretion System (T3SS2) that leads to massive cell death. However, the specific mechanism by which the T3SS2 induces cell death remains unclear and its contribution to mitochondrial stress is not fully understood. In this work, we evaluated the contribution of the T3SS2 of V. parahaemolyticus in generating mitochondrial stress during infection in human intestinal HT-29 cells. To evaluate the contribution of the T3SS2 of V. parahaemolyticus in mitochondrial stress, infection assays were carried out to evaluate mitochondrial transition pore opening, mitochondrial fragmentation, ATP quantification, and cell viability during infection. Our results showed that the Δvscn1 (T3SS2+) mutant strain contributes to generating the sustained opening of the mitochondrial transition pore. Furthermore, it generates perturbations in the ATP production in infected cells, leading to a significant decrease in cell viability and loss of membrane integrity. Our results suggest that the T3SS2 from V. parahaemolyticus plays a role in generating mitochondrial stress that leads to cell death in human intestinal HT-29 cells. It is important to highlight that this study represents the first report indicating the possible role of the V. parahaemolyticus T3SS2 and its effector proteins involvement in generating mitochondrial stress, its impact on the mitochondrial pore, and its effect on ATP production in human cells.

Rifampicin-resistant RpoB S522L Vibrio vulnificus exhibits disturbed stress response and hypervirulence traits

Rifampicin resistance, which is genetically linked to mutations in the RNA polymerase β-subunit gene rpoB, has a global impact on bacterial transcription and cell physiology. Previously, we identified a substitution of serine 522 in RpoB (i.e., RpoBS522L ) conferring rifampicin resistance to Vibrio vulnificus, a human food-borne and wound-infecting pathogen associated with a high mortality rate. Transcriptional and physiological analysis of V. vulnificus expressing RpoBS522L showed increased basal transcription of stress-related genes and global virulence regulators. Phenotypically these transcriptional changes manifest as disturbed osmo-stress responses and toxin-associated hypervirulence as shown by reduced hypoosmotic-stress resistance and enhanced cytotoxicity of the RpoBS522L strain. These results suggest that RpoB-linked rifampicin resistance has a significant impact on V. vulnificus survival in the environment and during infection.

Mitogen-Activated Protein Kinases (MAPKs) and Enteric Bacterial Pathogens: A Complex Interplay

Diverse extracellular and intracellular cues activate mammalian mitogen-activated protein kinases (MAPKs). Canonically, the activation starts at cell surface receptors and continues via intracellular MAPK components, acting in the host cell nucleus as activators of transcriptional programs to regulate various cellular activities, including proinflammatory responses against bacterial pathogens. For instance, binding host pattern recognition receptors (PRRs) on the surface of intestinal epithelial cells to bacterial pathogen external components trigger the MAPK/NF-κB signaling cascade, eliciting cytokine production. This results in an innate immune response that can eliminate the bacterial pathogen. However, enteric bacterial pathogens evolved sophisticated mechanisms that interfere with such a response by delivering virulent proteins, termed effectors, and toxins into the host cells. These proteins act in numerous ways to inactivate or activate critical components of the MAPK signaling cascades and innate immunity. The consequence of such activities could lead to successful bacterial colonization, dissemination, and pathogenicity. This article will review enteric bacterial pathogens' strategies to modulate MAPKs and host responses. It will also discuss findings attempting to develop anti-microbial treatments by targeting MAPKs.

Assessing the Effectiveness of Fermented Banana Peel Extracts for the Biosorption and Removal of Cadmium to Mitigate Inflammation and Oxidative Stress

This study identified 11 lactic acid bacteria (LAB) strains that exhibited tolerance to heavy metal cadmium concentrations above 50 ppm for 48 h. Among these strains, T126-1 and T40-1 displayed the highest tolerance, enduring cadmium concentrations up to 500 ppm while still inhibiting bacterial growth by 50%. Moreover, the fermentation of banana peel using LAB significantly enhanced the clearance rate of cadmium (p < 0.05) compared to nonfermented banana peel. Additionally, the LAB-fermented banana peel exhibited higher 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and reduced power values. Strain T40-1 exhibited a significant improvement in its ability to chelate ferrous ions (p < 0.05). Regarding antibiotic resistance, both the T40-1 and TH3 strains demonstrated high resistance with a third-level inhibition rate against ampicillin and tetracycline. Cell viability tests revealed that incubation with the T40-1 and TH3 strains for a duration of 24 h did not result in any cellular damage. Moreover, these LAB strains effectively mitigated oxidative stress markers, such as reactive oxygen species (ROS), glutathione (GSH), and lactate dehydrogenase (LDH), caused by 2 ppm cadmium on cells. Furthermore, the LAB strains were able to reduce the inflammatory response, as evidenced by a decrease in interleukin-8 (IL-8) levels (p < 0.05). The use of Fourier transform infrared (FT-IR) spectroscopy analysis provided valuable insight into the interaction between metal ions and the organic functional groups present on the cell wall of fermented banana peel. In summary, this study highlights the potential of the LAB strains T40-1 and TH3 in terms of their tolerance to the cadmium, ability to enhance cadmium clearance rates, and their beneficial effects on oxidative stress, inflammation, and cell viability.

In vivo characterisation of the Vibrio vulnificus stressosome: A complex involved in reshaping glucose metabolism and motility regulation, in nutrient- and iron-limited growth conditions

Stressosomes are signal-sensing and integration hubs identified in many bacteria. At present, the role of the stressosome has only been investigated in Gram-positive bacteria. This work represents the first in vivo characterisation of the stressosome in a Gram-negative bacterium, Vibrio vulnificus. Previous in vitro characterisation of the complex has led to the hypothesis of a complex involved in iron metabolism and control of c-di-GMP levels. We demonstrate that the stressosome is probably involved in reshaping the glucose metabolism in Fe- and nutrient-limited conditions and mutations of the locus affect the activation of the glyoxylate shunt. Moreover, we show that the stressosome is needed for the transcription of fleQ and to promote motility, consistent with the hypothesis that the stressosome is involved in regulating c-di-GMP. This report highlights the potential role of the stressosome in a Gram-negative bacterium, with implications for the metabolism and motility of this pathogen.

Targeting Virulence Factors of Candida albicans with Natural Products

Natural products derived from natural resources, including nutritional functional food, play an important role in human health. In recent years, the study of anti-fungal and other properties of agri-foods and derived functional compounds has been a hot research topic. Candida albicans is a parasitic fungus that thrives on human mucosal surfaces, which are colonized through opportunistic infection. It is the most prevalent cause of invasive fungal infection in immunocompromised individuals, resulting in a wide variety of clinical symptoms. Moreover, the efficacy of classical therapeutic medications such as fluconazole is often limited by the development of resistance. There is an ongoing need for the development of novel and effective antifungal therapy and medications. Infection of C. albicans is influenced by a great quantity of virulence factors, like adhesion, invasion-promoting enzymes, mycelial growth, and phenotypic change, and among others. Furthermore, various natural products especially from food sources that target C. albicans virulence factors have been researched, providing promising prospects for C. albicans prevention and treatment. In this review, we discuss the virulence factors of C. albicans and how functional foods and derived functional compounds affect them. Our hope is that this review will stimulate additional thoughts and suggestions regarding nutritional functional food and therapeutic development for patients afflicted with C. albicans.

Bis-Indole Alkaloids Isolated from the Sponge Spongosorites calcicola Disrupt Cell Membranes of MRSA

Antimicrobial resistance (AMR) is a global health challenge with methicillin resistant Staphylococcus aureus (MRSA), a leading cause of nosocomial infection. In the search for novel antibiotics, marine sponges have become model organisms as they produce diverse bioactive compounds. We investigated and compared the antibacterial potential of 3 bis-indole alkaloids—bromodeoxytopsentin, bromotopsentin and spongotine A—isolated from the Northeastern Atlantic sponge Spongosorites calcicola. Antimicrobial activity was determined by MIC and time-kill assays. The mechanism of action of bis-indoles was assessed using bacterial cytological profiling via fluorescence microscopy. Finally, we investigated the ability of bis-indole alkaloids to decrease the cytotoxicity of pathogens upon co-incubation with HeLa cells through the measurement of mammalian cell lysis. The bis-indoles were bactericidal to clinically relevant Gram-positive pathogens including MRSA and to the Gram-negative gastroenteric pathogen Vibrio parahaemolyticus. Furthermore, the alkaloids were synergistic in combination with conventional antibiotics. Antimicrobial activity of the bis-indole alkaloids was due to rapid disruption and permeabilization of the bacterial cell membrane. Significantly, the bis-indoles reduced pathogen cytotoxicity toward mammalian cells, indicating their ability to prevent bacterial virulence. In conclusion, sponge bis-indole alkaloids are membrane-permeabilizing agents that represent good antibiotic candidates because of their potency against Gram-positive and Gram-negative bacterial pathogens.

Vibrio harveyi infections induce production of proinflammatory cytokines in murine peritoneal macrophages via activation of p38 MAPK and NF-κB pathways, but reversed by PI3K/AKT pathways

Vibrio harveyi is a zoonotic pathogen that can infect humans through wounds and cause severe inflammatory responses. Previous studies have reported that the Toll like receptors (TLR) mediated MAPK, AKT and NF-κB signaling pathways are involved in innate immune system resistance to pathogen invasion. However, the molecular mechanism of these pathways, as well as their involvement in V. harveyi infection remains elusive. This study established a V. harveyi infection model using murine peritoneal macrophages (PMs). Various techniques, including western blotting, ELISA, RT-qPCR, immunofluorescence, inhibition assays, were used to explore the roles of TLRs, MAPK, AKT and NF-κB signaling pathways in V. harveyi-induced inflammatory responses. ELISA assays showed that V. harveyi infection triggered proinflammatory cytokines secretion in PMs. RT-qPCR and inhibition assays showed that TLR2 participated in V. harveyi infection and up-regulated the proinflammatory cytokines secretion in murine PMs. Western blotting data showed that the phosphorylation of p38, JNK, AKT, and NF-κB p65 were significantly increased partly mediated by TLR2. In addition, immunofluorescence assays revealed that the NF-κB p65 translocated into nucleus in response to V. harveyi infection. The secretion of IL-1β, IL-6, IL-12, and TNF-α were considerably reduced when the p38 MAPK and NF-κB signaling pathways were blocked, whereas blocking of AKT significantly increased the expression of IL-1β, IL-6, IL-12, and TNF-α. These findings indicate that V. harveyi infection induces inflammatory responses in murine PMs via activation of p38 MAPK and NF-κB pathways, which are partly mediated by TLR2, but are inhibited by PI3K/AKT pathways.

Delivering the pain: an overview of the type III secretion system with special consideration for aquatic pathogens

Gram-negative bacteria are known to subvert eukaryotic cell physiological mechanisms using a wide array of virulence factors, among which the type three-secretion system (T3SS) is often one of the most important. The T3SS constitutes a needle-like apparatus that the bacterium uses to inject a diverse set of effector proteins directly into the cytoplasm of the host cells where they can hamper the host cellular machinery for a variety of purposes. While the structure of the T3SS is somewhat conserved and well described, effector proteins are much more diverse and specific for each pathogen. The T3SS can remodel the cytoskeleton integrity to promote intracellular invasion, as well as silence specific eukaryotic cell signals, notably to hinder or elude the immune response and cause apoptosis. This is also the case in aquatic bacterial pathogens where the T3SS can often play a central role in the establishment of disease, although it remains understudied in several species of important fish pathogens, notably in Yersinia ruckeri. In the present review, we summarise what is known of the T3SS, with a special focus on aquatic pathogens and suggest some possible avenues for research including the potential to target the T3SS for the development of new anti-virulence drugs.

Interleukin-8 concentrations in obstructive sleep apnea syndrome: a systematic review and meta-analysis

Interleukin (IL)-8 has been shown to play an important role in obstructive sleep apnea syndrome (OSAS). However, its role in OSAS development is still controversial. This meta-analysis was to explore the correlation between interleukin (IL)-8 concentration and OSAS. Database (from the inception to July 2021) searches on PubMed, Web of Science, Medline, EMBASE, and Cochrane Library were conducted for studies analyzing the correlation between IL-8 concentration and OSAS, regardless of the language of publication. Standardized mean difference (SMD) and 95% confidence intervals (CI) were used to analyze any prospective association between IL-8 concentration and OSAS. A total of 25 eligible studies, including 2301 participants and 1123 controls, were included in this meta-analysis. The included studies evaluating the association between serum IL-8 concentration and OSAS indicated that adults and children with OSAS had elevated serum concentrations of IL-8 compared with controls (SMD = 0.997, 95% CI = 0.437–1.517, P < 0.001; SMD = 0.431, 95% CI = 0.104–0.759, P = 0.01). Categorization of the study population into subgroups according to body mass index, apnea–hypopnea index (AHI), ethnicity, and sample size also showed that individuals with OSAS had elevated serum concentrations of IL-8 compared with controls. Additionally, the results demonstrated that the higher the AHI, higher was the IL-8 concentration. Similar results were observed in the literature on the association between plasma IL-8 concentration and OSAS. This meta-analysis verified that compared with controls, children and adults with OSAS have significantly elevated IL-8 concentrations.

Identification of a Family of Vibrio Type III Secretion System Effectors That Contain a Conserved Serine/Threonine Kinase Domain

Vibrio parahaemolyticus is a marine Gram-negative bacterium that is a leading cause of seafood-borne gastroenteritis. Pandemic strains of V. parahaemolyticus rely on a specialized protein secretion machinery known as the type III secretion system 2 (T3SS2) to cause disease. The T3SS2 mediates the delivery of effector proteins into the cytosol of infected cells, where they subvert multiple cellular pathways. Here, we identify a new T3SS2 effector protein encoded by VPA1328 (VP_RS21530) in V. parahaemolyticus RIMD2210633. Bioinformatic analysis revealed that VPA1328 is part of a larger family of uncharacterized T3SS effector proteins with homology to the VopG effector protein in Vibrio cholerae AM-19226. These VopG-like proteins are found in many but not all T3SS2 gene clusters and are distributed among diverse Vibrio species, including V. parahaemolyticus, V. cholerae, V. mimicus, and V. diabolicus and also in Shewanella baltica. Structure-based prediction analyses uncovered the presence of a conserved C-terminal kinase domain in VopG orthologs, similar to the serine/threonine kinase domain found in the NleH family of T3SS effector proteins. However, in contrast to NleH effector proteins, in tissue culture-based infections, VopG did not impede host cell death or suppress interleukin 8 (IL-8) secretion, suggesting a yet undefined role for VopG during V. parahaemolyticus infection. Collectively, our work reveals that VopG effector proteins, a new family of likely serine/threonine kinases, is widely distributed in the T3SS2 effector armamentarium among marine bacteria. IMPORTANCE Vibrio parahaemolyticus is the leading bacterial cause of seafood-borne gastroenteritis worldwide. The pathogen relies on a type III secretion system to deliver a variety of effector proteins into the cytosol of infected cells to subvert cellular function. In this study, we identified a novel Vibrio parahaemolyticus effector protein that is similar to the VopG effector of Vibrio cholerae. VopG-like effectors were found in diverse Vibrio species and contain a conserved serine/threonine kinase domain that bears similarity to the kinase domain in the enterohemorrhagic Escherichia coli (EHEC) and Shigella NleH effectors that manipulate host cell survival pathways and host immune responses. Together our findings identify a new family of Vibrio effector proteins and highlight the role of horizontal gene transfer events among marine bacteria in shaping T3SS gene clusters.

Organism dual RNA-seq reveals the importance of BarA/UvrY in Vibrio parahaemolyticus virulence

Elucidation of host-pathogen interaction is essential for developing effective strategies to combat bacterial infection. Dual RNA-Seq using cultured cells or tissues/organs as the host of pathogen has emerged as a novel strategy to understand the responses concurrently from both pathogen and host at cellular level. However, bacterial infection mostly causes systematic responses from the host at organism level where the interplay is urgently to be understood but inevitably being neglected by the current practice. Here, we developed an approach that simultaneously monitor the genome-wide infection-linked transcriptional alterations in both pathogenic Vibrio parahaemolyticus and the infection host nematode Caenorhabditis elegans. Besides the dynamic alterations in transcriptomes of both C. elegans and V. parahaemolyticus during infection, we identify a two-component system, BarA/UvrY, that is important for virulence in host. BarA/UvrY not only controls the virulence factors in V. parahaemolyticus including Type III and Type VI secretion systems, but also attenuates innate immune responses in C. elegans, including repression on the MAP kinase-mediated cascades. Thus, our study exemplifies the use of dual RNA-Seq at organism level to uncover previously unrecognized interplay between host and pathogen.

Type III Secretion Effector VopQ of Vibrio parahaemolyticus Modulates Central Carbon Metabolism in Epithelial Cells

The metabolic response of host cells upon infection is pathogen specific, and infection-induced host metabolic reprogramming may have beneficial effects on the proliferation of pathogens. V. parahaemolyticus contains a range of virulence factors to manipulate host signaling pathways and metabolic processes. In this study, we identified that the T3SS1 VopQ effector rewrites host metabolism in conjunction with the inflammation and cell death processes. Understanding how VopQ reprograms host cell metabolism during the infection could help us to identify novel therapeutic strategies to enhance the survival of host cells during V. parahaemolyticus infection.

Vibrio parahaemolyticus is a Gram-negative halophilic pathogen that frequently causes acute gastroenteritis and occasional wound infection. V. parahaemolyticus contains several virulence factors, including type III secretion systems (T3SSs) and thermostable direct hemolysin (TDH). In particular, T3SS1 is a potent cytotoxic inducer, and T3SS2 is essential for causing acute gastroenteritis. Although much is known about manipulation of host signaling transductions by the V. parahaemolyticus effector, little is known about the host metabolomic changes modulated by V. parahaemolyticus. To address this knowledge gap, we performed a metabolomic analysis of the epithelial cells during V. parahaemolyticus infection using capillary electrophoresis-time of flight mass spectrometry (CE-TOF/MS). Our results revealed significant metabolomic perturbations upon V. parahaemolyticus infection. Moreover, we identified that T3SS1’s VopQ effector was responsible for inducing the significant metabolic changes in the infected cells. The VopQ effector dramatically altered the host cell’s glycolytic, tricarboxylic acid cycle (TCA), and amino acid metabolisms. VopQ effector disrupted host cell redox homeostasis by depleting cellular glutathione and subsequently increasing the level of reactive oxygen species (ROS) production.

IMPORTANCE The metabolic response of host cells upon infection is pathogen specific, and infection-induced host metabolic reprogramming may have beneficial effects on the proliferation of pathogens. V. parahaemolyticus contains a range of virulence factors to manipulate host signaling pathways and metabolic processes. In this study, we identified that the T3SS1 VopQ effector rewrites host metabolism in conjunction with the inflammation and cell death processes. Understanding how VopQ reprograms host cell metabolism during the infection could help us to identify novel therapeutic strategies to enhance the survival of host cells during V. parahaemolyticus infection.

In hot water: effects of climate change on Vibrio-human interactions

Sea level rise and the anthropogenic warming of the world's oceans is not only an environmental tragedy, but these changes also result in a significant threat to public health. Along with coastal flooding and the encroachment of saltwater farther inland comes an increased risk of human interaction with pathogenic Vibrio species, such as Vibrio cholerae, V. vulnificus and V. parahaemolyticus. This minireview examines the current literature for updates on the climatic changes and practices that impact the location and duration of the presence of Vibrio spp., as well as the infection routes, trends and virulence factors of these highly successful pathogens. Finally, an overview of current treatments and methods for the mitigation of both oral and cutaneous exposures are presented.

Molecular mechanisms of Vibrio parahaemolyticus pathogenesis

Vibrio parahaemolyticus is a Gram-negative halophilic bacterium that is mainly distributed in the seafood such as fish, shrimps and shellfish throughout the world. V. parahaemolyticus can cause diseases in marine aquaculture, leading to huge economic losses to the aquaculture industry. More importantly, it is also the leading cause of seafood-borne diarrheal disease in humans worldwide. With the development of animal model, next-generation sequencing as well as biochemical and cell biological technologies, deeper understanding of the virulence factors and pathogenic mechanisms of V. parahaemolyticus has been gained. As a globally transmitted pathogen, the pathogenicity of V. parahaemolyticus is closely related to a variety of virulence factors. This article comprehensively reviewed the molecular mechanisms of eight types of virulence factors: hemolysin, type III secretion system, type VI secretion system, adhesion factor, iron uptake system, lipopolysaccharide, protease and outer membrane proteins. This review comprehensively summarized our current understanding of the virulence factors in V. parahaemolyticus, which are potentially new targets for the development of therapeutic and preventive strategies.

Vibrio variations on a type three theme

Mounting evidence suggests that Type 3 Secretion Systems (T3SS) are widespread among Vibrio species, and are present in strains isolated from diverse sources such as human clinical infections, environmental reservoirs, and diseased marine life. Experiments evaluating Vibrio parahaemolyticus and Vibrio cholerae T3SS mediated virulence suggest that Vibrio T3SS pathogenicity islands have a tripartite composition. A conserved 'core' region encodes functions essential for colonization and disease in vivo, including modulation of innate immune signaling pathways and actin dynamics, whereas regions flanking core sequences are variable among strains and encode effector proteins performing a diverse array of activities. Characterizing novel functions associated with Vibrio-specific effectors is, therefore, essential for understanding how vibrios employ T3SS mechanisms to cause disease in a broad range of hosts and how T3SS island composition potentially defines species-specific disease.

QsvR integrates into quorum sensing circuit to control Vibrio parahaemolyticus virulence

Vibrio parahaemolyticus, the leading cause of seafood-associated gastroenteritis worldwide, requires the two type-III secretion systems (T3SS1 and T3SS2) and a thermostable direct hemolysin (encoded by tdh1 and tdh2) for full virulence. The tdh genes and the T3SS2 gene cluster constitute an 80 kb pathogenicity island known as Vp-PAI located on the chromosome II. Expression of T3SS1 and Vp-PAI is regulated in a quorum sensing (QS)-dependent manner but its detailed mechanisms remain unknown. Herein, we show that three factors (QS regulators AphA and OpaR and an AraC-type transcriptional regulator QsvR) form a complex regulatory network to control the expression of T3SS1 and Vp-PAI genes. At low cell density (LCD), whereas Vp-PAI expression is repressed, T3SS1 genes are induced by AphA, which directly binds (an operator region of) the exsBAD-vscBCD operon. At high cell density (HCD), the bacterium turns off T3SS1 expression by replacing AphA with OpaR, triggering the induction of Vp-PAI. Furthermore, QsvR binds to the regulatory regions of all the tested T3SS1 and Vp-PAI genes to activate their transcription at HCD. Taken together, our data highlight how multiple QS regulators contribute to the pathogenicity of V. parahaemolyticus by precisely controlling the expression of major virulence determinants during different stages of growth.

Evaluation of Lactic Acid Bacteria on the Inhibition of Vibrio parahaemolyticus Infection and Its Application to Food Systems

This study tested the effect of lactic acid bacteria (LAB) inhibition on Vibrio parahaemolyticus BCRC (Bioresource Collection and Research Center) 10806 and BCRC 12865 in a food model. MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays indicated that Caco-2 cells were not damaged after a two-hour treatment with lactic acid bacteria (LAB) and V. parahaemolyticus. The LAB cell culture and supernatant effectively inhibited the growth of V. parahaemolyticus in a food model. ELISA (Enzyme-linked immunosorbent assay) results indicated the significant inhibition of TNF-α; IL-1β; and IL-6; but Lactobacillus plantarum PM 222 and L. plantarum LP 735 did not significantly affect IL-8 levels. Real-time polymerase chain reaction (PCR) results indicated that LAB could inhibit the mRNA expression of proinflammatory cytokines IL-8; IL-6; and TNF-α; which were induced by V. parahaemolyticus. After rat-received LAB; the expression levels of TNF-α; IL-6; and IL-8 in the serum decreased significantly. In intestinal histology; the rat that received L. plantarum PM 222 and L. plantarum LP 010 was able to alleviate the intestinal villi damage caused by V. parahaemolyticus; which also helped reduce cell apoptosis. In conclusion; our results indicate that LAB can inhibit inflammatory responses caused by V. parahaemolyticus and can effectively inhibit the growth of V. parahaemolyticus in food products.

Regulatory actions of ToxR and CalR on their own genes and type III secretion system 1 in Vibrio parahaemolyticus

Vibrio parahaemolyticus is the leading cause of seafood-associated gastroenteritis. Type III secretion system 1 (T3SS1) is one of the virulence determinants of this bacteria. T3SS1 expression is regulated by ToxR and CalR. ToxR represses the transcription of T3SS1 genes via activation of CalR, which acts as a transcriptional repressor of T3SS1 genes. However, the transcriptional regulation mechanisms have not been elucidated. As showing in the present work, ToxR binds to the promoter DNA region of calR to activate its transcription. CalR occupies the promoter-proximal regions of each detected target operons in T3SS1 loci to repress their transcription, and thereby inhibiting T3SS1-dependent cytotoxicity. Moreover, a feedback CalR inhibits toxR and its own gene in a direct manner. Collectively, this work reported an interesting gene regulatory network involving the reciprocal regulation of ToxR and CalR, and their regulation on T3SS1 genes transcription in V. parahaemolyticus.

Characterization of V. cholerae T3SS-dependent cytotoxicity in cultured intestinal epithelial cells

AM-19226 is a pathogenic, non-O1/non-O139 serogroup strain of Vibrio cholerae that uses a Type 3 Secretion System (T3SS) mediated mechanism to colonize host tissues and disrupt homeostasis, causing cholera. Co-culturing the Caco2-BBE human intestinal epithelial cell line with AM-19226 in the presence of bile results in rapid mammalian cell death that requires a functional T3SS. We examined the role of bile, sought to identify the mechanism, and evaluated the contributions of T3SS translocated effectors in in vitro cell death. Our results suggest that Caco2-BBE cytotoxicity does not proceed by apoptotic or necrotic mechanisms, but rather displays characteristics consistent with osmotic lysis. Cell death was preceded by disassembly of epithelial junctions and reorganization of the cortical membrane skeleton, although neither cell death nor cell-cell disruption required VopM or VopF, two effectors known to alter actin dynamics. Using deletion strains, we identified a subset of AM-19226 Vops that are required for host cell death, which were previously assigned roles in protein translocation and colonization, suggesting that they function other than to promote cytotoxicity. The collective results therefore suggest that cooperative Vop activities are required to achieve cytotoxicity in vitro, or alternatively, that translocon pores destabilize the membrane in a bile dependent manner.

Comparative secretomics reveals novel virulence-associated factors of Vibrio parahaemolyticus

Vibrio parahaemolyticus is a causative agent of serious human seafood-borne gastroenteritis disease and even death. In this study, for the first time, we obtained the secretomic profiles of seven V. parahaemolyticus strains of clinical and food origins. The strains exhibited various toxic genotypes and phenotypes of antimicrobial susceptibility and heavy metal resistance, five of which were isolated from aquatic products in Shanghai, China. Fourteen common extracellular proteins were identified from the distinct secretomic profiles using the two-dimensional gel electrophoresis (2-DE) and liquid chromatography tandem mass spectrometry (LC-MS/MS) techniques. Of these, half were involved in protein synthesis and sugar transport of V. parahaemolyticus. Strikingly, six identified proteins were virulence-associated factors involved in the pathogenicity of some other pathogenic bacteria, including the translation elongation factor EF-Tu, pyridoxine 5′-phosphate synthase, σ⁵⁴ modulation protein, dihydrolipoyl dehydrogenase, transaldolase and phosphoglycerate kinase. In addition, comparative secretomics also revealed several extracellular proteins that have not been described in any bacteria, such as the ribosome-recycling factor, translation elongation factor EF-Ts, phosphocarrier protein HPr and maltose-binding protein MalE. The results in this study will facilitate the better understanding of the pathogenesis of V. parahaemolyticus and provide data in support of novel vaccine candidates against the leading seafood-borne pathogen worldwide.

The pathogenesis, detection, and prevention of Vibrio parahaemolyticus

Vibrio parahaemolyticus, a Gram-negative motile bacterium that inhabits marine and estuarine environments throughout the world, is a major food-borne pathogen that causes life-threatening diseases in humans after the consumption of raw or undercooked seafood. The global occurrence of V. parahaemolyticus accentuates the importance of investigating its virulence factors and their effects on the human host. This review describes the virulence factors of V. parahaemolyticus reported to date, including hemolysin, urease, two type III secretion systems and two type VI secretion systems, which both cause both cytotoxicity in cultured cells and enterotoxicity in animal models. We describe various types of detection methods, based on virulence factors, that are used for quantitative detection of V. parahaemolyticus in seafood. We also discuss some useful preventive measures and therapeutic strategies for the diseases mediated by V. parahaemolyticus, which can reduce, to some extent, the damage to humans and aquatic animals attributable to V. parahaemolyticus. This review extends our understanding of the pathogenic mechanisms of V. parahaemolyticus mediated by virulence factors and the diseases it causes in its human host. It should provide new insights for the diagnosis, treatment, and prevention of V. parahaemolyticus infection.

The focal complex of epithelial cells provides a signalling platform for interleukin-8 induction in response to bacterial pathogens

Bacterial pathogens can induce an inflammatory response from epithelial tissues due to secretion of the pro-inflammatory chemokine interleukin-8 (IL-8). Many bacterial pathogens manipulate components of the focal complex (FC) to induce signalling events in host cells. We examined the interaction of several bacterial pathogens with host cells, including Campylobacter jejuni, to determine if the FC is required for induction of chemokine signalling in response to bacterial pathogens. Our data indicate that secretion of IL-8 is triggered by C. jejuni, Helicobacter pylori and Salmonella enterica serovar Typhimurium in response to engagement of β1 integrins. Additionally, we found that the secretion of IL-8 from C. jejuni infected epithelial cells requires FAK, Src and paxillin, which in turn are necessary for Erk 1/2 recruitment and activation. Targeting the FC component paxillin with siRNA prevented IL-8 secretion from cells infected with several bacterial pathogens, including C. jejuni, Helicobacter pylori, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Pseudomonas aeruginosa, and Vibrio parahaemolyticus. Our findings indicate that maximal IL-8 secretion from epithelial cells in response to bacterial infection is dependent on the FC. Based on the commonality of the host response to bacterial pathogens, we propose that the FC is a signalling platform for an epithelial cell response to pathogenic organisms.

Molecular diversity and predictability of Vibrio parahaemolyticus along the Georgian coastal zone of the Black Sea

Vibrio parahaemolyticus is a leading cause of seafood-related gastroenteritis and is also an autochthonous member of marine and estuarine environments worldwide. One-hundred seventy strains of V. parahaemolyticus were isolated from water and plankton samples collected along the Georgian coast of the Black Sea during 28 months of sample collection. All isolated strains were tested for presence of tlh, trh, and tdh. A subset of strains were serotyped and tested for additional factors and markers of pandemicity. Twenty-six serotypes, five of which are clinically relevant, were identified. Although all 170 isolates were negative for tdh, trh, and the Kanagawa Phenomenon, 7 possessed the GS-PCR sequence and 27 the 850 bp sequence of V. parahaemolyticus pandemic strains. The V. parahaemolyticus population in the Black Sea was estimated to be genomically heterogeneous by rep-PCR and the serodiversity observed did not correlate with rep-PCR genomic diversity. Statistical modeling was used to predict presence of V. parahaemolyticus as a function of water temperature, with strongest concordance observed for Green Cape site samples (Percent of total variance = 70, P < 0.001). Results demonstrate a diverse population of V. parahaemolyticus in the Black Sea, some of which carry pandemic markers, with increased water temperature correlated to an increase in abundance of V. parahaemolyticus.

Manipulation of intestinal epithelial cell function by the cell contact-dependent type III secretion systems of Vibrio parahaemolyticus

Vibrio parahaemolyticus elicits gastroenteritis by deploying Type III Secretion Systems (TTSS) to deliver effector proteins into epithelial cells of the human intestinal tract. The bacteria must adhere to the human cells to allow colonization and operation of the TTSS translocation apparatus bridging the bacterium and the host cell. This article first reviews recent advances in identifying the molecules responsible for intercellular adherence. V. parahaemolyticus possesses two TTSS, each of which delivers an exclusive set of effectors and mediates unique effects on the host cell. TTSS effectors primarily target and alter the activation status of host cell signaling proteins, thereby bringing about changes in the regulation of cellular behavior. TTSS1 is responsible for the cytotoxicity of V. parahaemolyticus, while TTSS2 is necessary for the enterotoxicity of the pathogen. Recent publications have elucidated the function of several TTSS effectors and their importance in the virulence of the bacterium. This review will explore the ability of the TTSS to manipulate activities of human intestinal cells and how this modification of cell function favors bacterial colonization and persistence of V. parahaemolyticus in the host.

Serine phosphorylation of cortactin is required for maximal host cell invasion by Campylobacter jejuni

BACKGROUND

Campylobacter jejuni causes acute disease characterized by severe diarrhea containing blood and leukocytes, fever, and abdominal cramping. Disease caused by C. jejuni is dependent on numerous bacterial and host factors. C. jejuni invasion of the intestinal epithelial cells is seen in both clinical samples and animal models indicating that host cell invasion is, in part, necessary for disease. C. jejuni utilizes a flagellar Type III Secretion System (T3SS) to deliver the Campylobacter invasion antigens (Cia) to host cells. The Cia proteins modulate host cell signaling leading to actin cytoskeleton rearrangement necessary for C. jejuni host cell invasion, and are required for the development of disease.

RESULTS

This study was based on the hypothesis that the C. jejuni CiaD effector protein mediates Erk 1/2 dependent cytoskeleton rearrangement. We showed that CiaD was required for the maximal phosphorylation of Erk 1/2 by performing an immunoblot with a p-Erk 1/2 specific antibody and that Erk 1/2 participates in C. jejuni invasion of host cells by performing the gentamicin protection assay in the presence and absence of the PD98059 (a potent inhibitor of Erk 1/2 activation). CiaD was also found to be required for the maximal phosphorylation of cortactin S405 and S418, as judged by immunoblot analysis. The response of human INT 407 epithelial cells to infection with C. jejuni was evaluated by confocal microscopy and scanning electron microscopy to determine the extent of membrane ruffling. This analysis revealed that CiaD, Erk 1/2, and cortactin participate in C. jejuni-induced membrane ruffling. Finally, cortactin and N-WASP were found to be involved in C. jejuni invasion of host cells using siRNA to N-WASP, and siRNA to cortactin, coupled with the gentamicin protection assay.

CONCLUSION

We conclude that CiaD is involved in the activation of Erk 1/2 and that activated Erk 1/2 facilitates C. jejuni invasion by phosphorylation of cortactin on serine 405 and 418. This is the first time that cortactin and N-WASP have been shown to be involved in C. jejuni invasion of host cells. These data also provide a mechanistic basis for the requirement of Erk 1/2 in C. jejuni-mediated cytoskeletal rearrangement.

The Campylobacter jejuni CiaD effector protein activates MAP kinase signaling pathways and is required for the development of disease

Background

Enteric pathogens utilize a distinct set of proteins to modulate host cell signaling events that promote host cell invasion, induction of the inflammatory response, and intracellular survival. Human infection with Campylobacter jejuni, the causative agent of campylobacteriosis, is characterized by diarrhea containing blood and leukocytes. The clinical presentation of acute disease, which is consistent with cellular invasion, requires the delivery of the Campylobacter invasion antigens (Cia) to the cytosol of host cells via a flagellar Type III Secretion System (T3SS). We identified a novel T3SS effector protein, which we termed CiaD that is exported from the C. jejuni flagellum and delivered to the cytosol of host cells.

Results

We show that the host cell kinases p38 and Erk 1/2 are activated by CiaD, resulting in the secretion of interleukin-8 (IL-8) from host cells. Additional experiments revealed that CiaD-mediated activation of p38 and Erk 1/2 are required for maximal invasion of host cells by C. jejuni. CiaD contributes to disease, as evidenced by infection of IL-10 knockout mice. Noteworthy is that CiaD contains a Mitogen-activated protein (MAP) kinase-docking site that is found within effector proteins produced by other enteric pathogens. These findings indicate that C. jejuni activates the MAP kinase signaling pathways Erk 1/2 and p38 to promote cellular invasion and the release of the IL-8 pro-inflammatory chemokine.

Conclusions

The identification of a novel T3SS effector protein from C. jejuni significantly expands the knowledge of virulence proteins associated with C. jejuni pathogenesis and provides greater insight into the mechanism utilized by C. jejuni to invade host cells.

Vibrio effector protein, VopQ, forms a lysosomal gated channel that disrupts host ion homeostasis and autophagic flux

Defects in normal autophagic pathways are implicated in numerous human diseases--such as neurodegenerative diseases, cancer, and cardiomyopathy--highlighting the importance of autophagy and its proper regulation. Herein we show that Vibrio parahaemolyticus uses the type III effector VopQ (Vibrio outer protein Q) to alter autophagic flux by manipulating the partitioning of small molecules and ions in the lysosome. This effector binds to the conserved Vo domain of the vacuolar-type H(+)-ATPase and causes deacidification of the lysosomes within minutes of entering the host cell. VopQ forms a gated channel ∼18 Å in diameter that facilitates outward flux of ions across lipid bilayers. The electrostatic interactions of this type 3 secretion system effector with target membranes dictate its preference for host vacuolar-type H(+)-ATPase-containing membranes, indicating that its pore-forming activity is specific and not promiscuous. As seen with other effectors, VopQ is exploiting a eukaryotic mechanism, in this case manipulating lysosomal homeostasis and autophagic flux through transmembrane permeation.

A Vibrio parahaemolyticus T3SS effector mediates pathogenesis by independently enabling intestinal colonization and inhibiting TAK1 activation

Vibrio parahaemolyticus type III secretion system 2 (T3SS2) is essential for the organism's virulence, but the effectors required for intestinal colonization and induction of diarrhea by this pathogen have not been identified. Here, we identify a type III secretion system (T3SS2)-secreted effector, VopZ, that is essential for V. parahaemolyticus pathogenicity. VopZ plays distinct, genetically separable roles in enabling intestinal colonization and diarrheagenesis. Truncation of VopZ prevents V. parahaemolyticus colonization, whereas deletion of VopZ amino acids 38-62 abrogates V. parahaemolyticus-induced diarrhea and intestinal pathology but does not impair colonization. VopZ inhibits activation of the kinase TAK1 and thereby prevents the activation of MAPK and NF-κB signaling pathways, which lie downstream. In contrast, the VopZ internal deletion mutant cannot counter the activation of pathways regulated by TAK1. Collectively, our findings suggest that VopZ's inhibition of TAK1 is critical for V. parahaemolyticus to induce diarrhea and intestinal pathology.

Persistence of Vibrio parahaemolyticus in the Pacific oyster, Crassostrea gigas, is a multifactorial process involving pili and flagella but not type III secretion systems or phase variation

Vibrio parahaemolyticus can resist oyster depuration, suggesting that it possesses specific factors for persistence. We show that type I pili, type IV pili, and both flagellar systems contribute to V. parahaemolyticus persistence in Pacific oysters whereas type III secretion systems and phase variation do not.

Virulence determinants for Vibrio parahaemolyticus infection

Vibrio parahaemolyticus is a marine microorganism that causes acute gastroenteritis associated with the consumption of contaminated raw or under cooked seafood. During infection, the bacterium utilizes a wide variety of virulence factors, including adhesins, toxins and type III secretion systems, to cause both cytotoxicity in cultured cells and enterotoxicity in animal models. Herein, we describe recent discoveries on the regulation and characterization of the virulence factors from V. para. Determining how this bacterial pathogen uses virulence factors to mediate pathogenicity improves our understanding of V. para. infections and more generally, host-pathogen interactions.

Vibrio parahaemolyticus ExsE is requisite for initial adhesion and subsequent type III secretion system 1-dependent autophagy in HeLa cells

Vibrio parahaemolyticus pandemic serotype O3 : K6 causes acute gastroenteritis, wound infections and septicaemia in humans. This organism encodes two type III secretion systems (T3SS1 and T3SS2); host-cell cytotoxicity has been attributed to T3SS1. Synthesis and secretion of T3SS1 proteins is positively regulated by ExsA, which is presumptively regulated by the ExsCDE pathway, similar to Pseudomonas aeruginosa. Herein we deleted the putative exsE from V. parahaemolyticus and found constitutive expression of the T3SS1 in broth culture as expected. More importantly, however, in a cell culture model, the ΔexsE strain was unable to induce cytotoxicity, as measured by release of lactate dehydrogenase (LDH), or autophagy, as measured by LC3 conversion. This is markedly different from P. aeruginosa, where deletion of exsE has no effect on host-cell cytolysis. Swarming and cytoadhesion were reduced for the deletion mutant and could be recovered along with T3SS1-induced HeLa cell cytotoxicity by in cis expression of exsE in the ΔexsE strain. Loss of adhesion and swarming motility was associated with the loss of flagella biogenesis in the exsE-deficient strain. Mouse mortality was unaffected by the deletion of exsE compared with a wild-type control, suggesting that additional adhesins are important for intoxication in vivo. Based on these data, we conclude that ExsE contributes to the negative regulation of T3SS1 and, in addition, contributes to regulation of an adherence phenotype that is requisite for translocation of effector proteins into HeLa cells.

The Vibrio parahaemolyticus ToxRS regulator is required for stress tolerance and colonization in a novel orogastric streptomycin-induced adult murine model

Vibrio parahaemolyticus, a marine bacterium, is the causative agent of gastroenteritis associated with the consumption of seafood. It contains a homologue of the toxRS operon that in V. cholerae is the key regulator of virulence gene expression. We examined a nonpolar mutation in toxRS to determine the role of these genes in V. parahaemolyticus RIMD2210633, an O3:K6 isolate, and showed that compared to the wild type, ΔtoxRS was significantly more sensitive to acid, bile salts, and sodium dodecyl sulfate stresses. We demonstrated that ToxRS is a positive regulator of ompU expression, and that the complementation of ΔtoxRS with ompU restores stress tolerance. Furthermore, we showed that ToxRS also regulates type III secretion system genes in chromosome I via the regulation of the leuO homologue VP0350. We examined the effect of ΔtoxRS in vivo using a new orogastric adult murine model of colonization. We demonstrated that streptomycin-treated adult C57BL/6 mice experienced prolonged intestinal colonization along the entire intestinal tract by the streptomycin-resistant V. parahaemolyticus. In contrast, no colonization occurred in non-streptomycin-treated mice. A competition assay between the ΔtoxRS and wild-type V. parahaemolyticus strains marked with the β-galactosidase gene lacZ demonstrated that the ΔtoxRS strain was defective in colonization compared to the wild-type strain. This defect was rescued by ectopically expressing ompU. Thus, the defect in stress tolerance and colonization in ΔtoxRS is solely due to OmpU. To our knowledge, the orogastric adult murine model reported here is the first showing sustained intestinal colonization by V. parahaemolyticus.

Vibrio parahaemolyticus cell biology and pathogenicity determinants

Vibrio parahaemolyticus is a significant cause of gastroenteritis worldwide. Characterization of this pathogen has revealed a unique repertoire of virulence factors that allow for colonization of the human host and disease. The following describes the known pathogenicity determinants while establishing the need for continued research.