Vibrio mimicus Lineage Carrying Cholera Toxin and Vibrio Pathogenicity Island, United States and China.

Vibrio mimicus bacteria have caused sporadic cases and outbreaks of cholera-like diarrhea throughout the world, but the association of lineages with such events is unexplored. Genomic analyses revealed V. mimicus lineages carrying the virulence factors cholera toxin and toxin coregulated pilus, one of which has persisted for decades in China and the United States.

rpoS involved in immune response of Macrobrachium nipponens to Vibrio mimicus infection.

Vibrio mimicus is a pathogenic bacterium that cause red body disease in Macrobrachium nipponense, leading to high mortality and financial loss. Based on previous studies, rpoS gene contribute to bacterial pathogenicity during infection, but the role of RpoS involved in the immune response of M. nipponense under V. mimicus infection remains unclear. In this study, the pathogen load and the RNA-seq of M. nipponense under wild-type and ΔrpoS strain V. mimicus infection were investigated. Over the entire infection period, the ΔrpoS strain pathogen load was always lower than that of the wild-type strain in the M. nipponense hemolymph, hepatopancreas, gill and muscle. Furthermore, the expression level of rpoS gene in the hepatopancreas was the highest at 24 hours post infection (hpi), then the samples of hepatopancreas tissue infected with the wild type and ΔrpoS strain at 24 hpi were selected for RNA-seq sequencing. The results revealed a significant change in the transcriptomes of the hepatopancreases infected with ΔrpoS strain. In contrast to the wild-type infected group, the ΔrpoS strain infected group exhibited differentially expressed genes (DEGs) enriched in 181 KEGG pathways at 24 hpi. Among these pathways, 8 immune system-related pathways were enriched, including ECM-receptor interaction, PI3K-Akt signaling pathway, Rap1 signaling pathway, Gap junction, and Focal adhesion, etc. Among these pathways, up-regulated genes related to Kazal-type serine protease inhibitors, S-antigen protein, copper zinc superoxide dismutase, tight junction protein, etc. were enriched. This study elucidates that rpoS can affect tissue bacterial load and immune-related pathways, thereby impacting the survival rate of M. nipponense under V. mimicus infection. These findings validate the potential of rpoS as a promising target for the development of a live attenuated vaccine against V. mimicus.

Exploitation of multiple host-derived nutrients by the yellow catfish epidermal environment facilitates Vibrio mimicus to sustain infection potency and susceptibility.

Infection with Vibrio mimicus in the Siluriformes has demonstrated a rapid and high infectivity and mortality rate, distinct from other hosts. Our earlier investigations identified necrosis, an inflammatory storm, and tissue remodeling as crucial pathological responses in yellow catfish (Pelteobagrus fulvidraco) infected with V. mimicus. The objective of this study was to further elucidate the impact linking these pathological responses within the host during V. mimicus infection. Employing metabolomics and transcriptomics, we uncovered infection-induced dense vacuolization of perimysium; Several genes related to nucleosidase and peptidase activities were significantly upregulated in the skin and muscles of infected fish. Concurrently, the translation processes of host cells were impaired. Further investigation revealed that V. mimicus completes its infection process by enhancing its metabolism, including the utilization of oligopeptides and nucleotides. The high susceptibility of yellow catfish to V. mimicus infection was associated with the composition of its body surface, which provided a microenvironment rich in various nucleotides such as dIMP, dAMP, deoxyguanosine, and ADP, in addition to several amino acids and peptides. Some of these metabolites significantly boost V. mimicus growth and motility, thus influencing its biological functions. Furthermore, we uncovered an elevated expression of gangliosides on the surface of yellow catfish, aiding V. mimicus adhesion and increasing its infection risk. Notably, we observed that the skin and muscles of yellow catfish were deficient in over 25 polyunsaturated fatty acids, such as Eicosapentaenoic acid, 12-oxo-ETE, and 13-Oxo-ODE. These substances play a role in anti-inflammatory mechanisms, possibly contributing to the immune dysregulation observed in yellow catfish. In summary, our study reveals a host immune deviation phenomenon that promotes bacterial colonization by increasing nutrient supply. It underscores the crucial factors rendering yellow catfish highly susceptible to V. mimicus, indicating that host nutritional sources not only enable the establishment and maintenance of infection within the host but also aid bacterial survival under immune pressure, ultimately completing its lifecycle.

Seafood-Associated Outbreak of ctx-Negative Vibrio mimicus Causing Cholera-Like Illness, Florida, USA.

Vibrio mimicus caused a seafood-associated outbreak in Florida, USA, in which 4 of 6 case-patients were hospitalized; 1 required intensive care for severe diarrhea. Strains were ctx-negative but carried genes for other virulence determinants (hemolysin, proteases, and types I-IV and VI secretion systems). Cholera toxin-negative bacterial strains can cause cholera-like disease.

Isolation and genomic characterization of Vmp-1 using Vibrio mimicus as the host: A novel virulent bacteriophage capable of cross-species lysis against three Vibrio spp.

Vibrio mimicus is a zoonotic pathogen that is widely distributed in aquatic habitats/environments (marine coastal water, estuaries, etc). The development of biocontrol agents for V. mimicus is imperative for the prevention and control of aquatic animal diseases and human food-borne infections. In this study, a broad-spectrum bacteriophage Vmp-1 was isolated from dealt aquatic product in a local market by double-layer agar plate method using V. mimicus CICC21613 as the host bacteria. Results indicated that Vmp-1, which belongs to the family Podoviridae, showed good pH tolerance (pH 3.0-12.0) and thermal stability (30-50 °C). The optimal multiplicity of infection (MOI) of Vmp-1 was 0.001 for a 20-min incubation and 100-min lysis period. Vmp-1 effectively controlled V. mimicus CICC21613 in LBS model (MOI = 0.0001, 0.001, 0.01, 0.1, 1) within 8 h. The full length of the Vmp-1 genome was 43,312 bp, with average GC content of 49.5%, and a total of 44 protein-coding regions. This study provides a novel phage strain that has the highest homology with vB_VpP_HA5 (GenBank: OK585159.1, 95.96%) for the development of biocontrol agents for V. mimicus.

Unraveling extracellular protein signatures to enhance live attenuated vaccine development through type II secretion system disruption in Vibriomimicus.

Type II secretion systems (T2SS) are important molecular machines used by bacteria to transport a wide range of proteins across the outer membrane from the periplasm. Vibrio mimicus is an epidemic pathogen threats to both aquatic animals and human health. Our previous study demonstrates that T2SS deletion reduced virulence by 307.26 times in yellow catfish. However, the specific effects of T2SS-mediated extracellular protein secretion in V. mimicus, including its potential role in exotoxin secretion or other mechanisms, require further investigation. Through proteomics and phenotypic analyses, this study observed that the ΔT2SS strain exhibited significant self-aggregation and dynamic deficiency, with a notable negative correlation with subsequent biofilm formation. The proteomics analysis revealed 239 different abundances of extracellular proteins after T2SS deletion, including 19 proteins with higher abundance and 220 proteins with lower and even absent in the ΔT2SS strain. These extracellular proteins are involved in various pathways, such as metabolism, virulence factors expression, and enzymes. Among them, purine, pyruvate, and pyrimidine metabolism, and the Citrate cycle, were the primary pathways affected by T2SS. Our phenotypic analysis is consistent with these findings, suggesting that the decreased virulence of ΔT2SS strains is due to the effect of T2SS on these proteins, which negatively impacts growth, biofilm formation, auto-aggregation, and motility of V. mimicus. These results provide valuable insights for designing deletion targets for attenuated vaccines development against V. mimicus and expand our understanding of the biological functions of T2SS.

Lc-pPG-612-OmpU-CTB: A promising oral vaccine for protecting Carassius auratus against Vibrio mimicus infection.

Vibrio mimicus (V. mimicus) is known to cause severe bacterial diseases with high mortality rates in fish, resulting in significant economic losses in the global aquaculture industry. Therefore, the objective of this study was to develop a safe and effective vaccine for protecting Carassius auratus (C. auratus) against V. mimicus infection. Recombinant Lactobacillus casei (L. casei) strains, Lc-pPG-612-OmpU and Lc-pPG-612-OmpU-CTB (surface-displayed), were constructed using a L. casei strain (ATCC 393) as an antigen delivery carrier and the cholera toxin B subunit (CTB) as an adjuvant. The two recombinant strains of L. casei were administered to C. auratus via oral immunization, and the protective efficacy of the oral vaccines was assessed. The results demonstrated that oral immunization with the two strains significantly increased the levels of nonspecific immune indicators in C. auratus, including alkaline phosphatase (AKP), lysozyme (LYS), acid phosphatase (ACP), complement 3 (C3), complement 4 (C4), lectin, and superoxide dismutase (SOD). Moreover, the experiment groups exhibited significant increases in specific immunoglobulin M (IgM) antibodies against OmpU, as well as the transcription of immune-related genes (ie., IL-1ß, TNF-α, IL-10, and TGF-ß), when compared to the control groups. Following infection of C. auratus with V. mimicus, the mortality rate of the recombinant L. casei-treated fish was observed to be lower compared to the control group. This finding suggests that recombinant L. casei demonstrates effective protection against V. mimicus infection in C. auratus. Furthermore, the addition of the immune adjuvant CTB was found to induce a more robust adaptive and innate immune response in C. auratus, resulting in reduced mortality after infection with V. mimicus.

Oral vaccination with recombinant Lactobacillus casei with surface displayed OmpK fused to CTB as an adjuvant against Vibrio mimicus infection in Carassius auratus.

Vibrio mimicus (V. mimicus) is a pathogenic bacterium that causes diseases in humans and various aquatic animals. A particularly efficient way to provide protection against V. mimicus is through vaccination. However, there are few commercial vaccines against V. mimics, especially oral vaccines. In our study, two surface-display recombinant Lactobacillus casei (L. casei) Lc-pPG-OmpK and Lc-pPG-OmpK-CTB were constructed using L. casei ATCC393 as an antigen delivery vector, outer membrane protein K (OmpK) of V. mimicus as an antigen, and cholera toxin B subunit (CTB) as a molecular adjuvant; furthermore, the immunological effects of recombinant L.casei in Carassius auratus (C. auratus) were assessed. The results indicated that oral recombinant L.casei Lc-pPG-OmpK and Lc-pPG-OmpK-CTB stimulated higher levels of serum-specific immunoglobulin M (IgM) and increased the activity of acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD), lysozyme (LYS), lectin, C3, and C4 in C. auratus, compared with control groups (Lc-pPG group and PBS group). Furthermore, the expression of interleukin-1ß (IL-1ß), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and transforming growth factor-ß (TGF-ß) in the liver, spleen, head kidney, hind intestine and gills of C. auratus was significantly increased, compared with that in the controls. These results demonstrated that the two recombinant L. casei strains could effectively trigger humoral and cellular immunity in C. auratus. In addition, two recombinant L.casei strains were able to survive and colonize the intestine of C. auratus. Importantly, after being challenged with V. mimicus, C. auratus fed Lc-pPG-OmpK and Lc-pPG-OmpK-CTB exhibited greater survival rates than the controls (52.08% and 58.33%, respectively). The data showed that recombinant L. casei could elicit a protective immunological response in C. auratus. The effect of the Lc-pPG-OmpK-CTB group was better than that of the Lc-pPG-OmpK group, and Lc-pPG-OmpK-CTB was found to be an effective candidate for oral vaccination.

Interleukin-1ß enhances the expression of two antimicrobial peptides in grass carp (Ctenopharyngodon idella) against Vibrio mimicus via activating NF-κB pathway.

Vibrio mimicus (V. mimicus) is a pathogen causing serious vibriosis in aquatic animals. Hepcidin and ß-Defensin1 are two important antibacterial peptides (AMPs) with broad-spectrum antibacterial activity in fish. In mammals, some evidences demonstrated that interleukin-1ß (IL-1ß) primarily promote AMPs expression via activating classical NF-κB pathway, but it still remains unclear in fish. Here, the temporal and spatial expression patterns of grass carp IL-1ß (gcIL-1ß) gene and two AMPs genes (gchepcidin and gcß-defensin1) in tissues post-V. mimicus infection and anti-V. mimicus activity of these two AMPs in vitro were detected, showing that V. mimicus infection significantly elevated the mRNA levels of these three genes in the immune-related tissues although their expression patterns were not entirely consistent, and both gcHepcidin and gcß-Defensin1 possessed anti-V. mimicus activity in vitro. Subsequently, the recombinant gcIL-1ß (rgcIL-1ß) was expressed prokaryotically in an inclusion body, which could promote proliferation of grass carp head kidney leukocytes (gcHKLs) and enhance respiratory burst activity and phagocytic activity of head kidney macrophages. Stimulation with rgcIL-1ß was able to significantly regulate the mRNA expression of key regulatory genes (il-1RI, traf6, tak1, ikkß, iκBα and p65) involved in the activation of classical NF-κB pathway, and then induce gcTAK1 phosphorylation, promote gcp65 nuclear translocation and enhance endogenous gcIL-1ß expression at both mRNA and protein levels, implying NF-κB pathway was activated. More importantly, exogenous rgcIL-1ß stimulation also significantly up-regulated both gcHepcidin and gcß-Defensin1 mRNA levels against V. mimicus, and the regulatory effect was blocked or inhibited by NF-κB inhibitor PDTC. Taken together, our results demonstrated for the first time that grass carp IL-1ß stimulation could significantly enhance the expression of these two anti-V.mimicus AMPs via activating classical NF-κB pathway.

Second extracellular protease mediating maturation of Vibrio mimicus hemolysin.

Vibrio mimicus is a bacterium that causes gastroenteritis in humans. This pathogen produces an enterotoxic hemolysin called V. mimicus hemolysin (VMH), which is secreted extracellularly as an inactive 80-kDa protoxin and converted to a 66-kDa mature toxin through cleavage between Arg151 and Ser152. The 56-kDa serine protease termed V. mimicus trypsin-like protease (VmtA) is known to mediate this maturating process. However, some strains including strain ES-20 does not possess the vmtA gene. In the present study, the vmtA-negative strains were found to have a replaced gene that encodes a 43-kDa (403 aa) precursor of a serine protease designated by VmtX (V. mimicus trypsin-like protease X). To examine whether VmtX is also involved in the maturation of VMH, VmtX was isolated from the culture supernatant of V. mimicus strain NRE-20, a metalloprotease-negative mutant constructed from strain ES-20. Concretely, the culture supernatant was fractionated with 70% saturated ammonium sulfate and subjected to affinity column chromatography using a HiTrap Benzamidine FF column. The analysis of the N-terminal amino acid sequences of the proteins in the obtained VmtX preparation indicated that the 39-kDa protein was active VmtX consisting of 371 aa (Ile33-Ser403). The VmtX preparation was found to activate pro-VMH through generation of the 66-kDa protein. Additionally, treatment of the VmtX preparation with serine protease inhibitors, such as leupeptin and phenylmethylsulfonyl fluoride, significantly suppressed the activities to hydrolyze the specific peptide substrate and to synthesize the 66-kDa toxin. These findings indicate that VmtX is the second protease that mediats the maturation of VMH.

Immunogenicity study of OmpU subunit vaccine against Vibrio mimicus in yellow catfish, Pelteobagrus fulvidraco.

The outer membrane protein U (OmpU) is a conserved outer membrane protein in a variety of pathogenic Vibrio species and has been considered as a vital protective antigen for vaccine development. Vibrio mimicus (V. mimicus) is the pathogen causing ascites disease in aquatic animals. In this study, the prokaryotically expressed and purified His-tagged OmpU of V. mimicus (His-OmpU) was used as a subunit vaccine. The formalin inactivated V. mimicus, purified His tag (His-tag), and PBS were used as controls. The vaccinated yellow catfish were challenged with V. mimicus at 28 days post-vaccination, and the results showed that the His-OmpU and inactivated V. mimicus groups exhibited much higher survival rates than the His-tag and PBS groups. To fully understand the underlying mechanism, we detected the expression levels of several immune-related genes in the spleen of fish at 28 days post-vaccination and 24 h post-challenge. The results showed that most of the detected immune-related genes were significantly upregulated in His-OmpU and inactivated V. mimicus groups. In addition, we performed the serum bactericidal activity assay, and the results showed that the serum from His-OmpU and inactivated V. mimicus groups exhibited much stronger bactericidal activity against V. mimicus than those of His-tag and PBS groups. Finally, the serum agglutination antibody was detected, and the antibody could be detected in His-OmpU and inactivated V. mimicus groups with the antibody titers increasing along with the time post-vaccination, but not in His-tag or PBS group. Our data reveal that the recombinant OmpU elicits potent protective immune response and is an effective vaccine candidate against V. mimicus in yellow catfish.

Novel Cholera Toxin Variant and ToxT Regulon in Environmental Vibrio mimicus Isolates: Potential Resources for the Evolution of Vibrio cholerae Hybrid Strains.

Atypical El Tor strains of Vibrio cholerae O1 harboring variant ctxB genes of cholera toxin (CT) have gradually become a major cause of recent cholera epidemics. Vibrio mimicus occasionally produces CT, encoded by ctxAB on CTXФ genome; toxin-coregulated pilus (TCP), a major intestinal colonization factor; and also the CTXФ-specific receptor. This study carried out extensive molecular characterization of CTXФ and ToxT regulon in V. mimicusctx-positive (ctx+) strains (i.e., V. mimicus strains containing ctx) isolated from the Bengal coast. Southern hybridization, PCR, and DNA sequencing of virulence-related genes revealed the presence of an El Tor type CTX prophage (CTXET) carrying a novel ctxAB, tandem copies of environmental type pre-CTX prophage (pre-CTXEnv), and RS1 elements, which were organized as an RS1-CTXET-RS1-pre-CTXEnv-pre-CTXEnv array. Additionally, novel variants of tcpA and toxT, respectively, showing phylogenetic lineage to a clade of V. cholerae non-O1 and to a clade of V. cholerae non-O139, were identified. The V. mimicus strains lacked the RTX (repeat in toxin) and TLC (toxin-linked cryptic) elements and lacked Vibrio seventh-pandemic islands of the El Tor strains but contained five heptamer (TTTTGAT) repeats in ctxAB promoter region similar to those seen with some classical strains of V. cholerae O1. Pulsed-field gel electrophoresis (PFGE) analysis showed that all the ctx+V. mimicus strains were clonally related. However, their in vitro CT production and in vivo toxigenicity characteristics were variable, which could be explainable by differential transcription of virulence genes along with the ToxR regulon. Taken together, our findings strongly suggest that environmental V. mimicus strains act as a potential reservoir of atypical virulence factors, including variant CT and ToxT regulons, and may contribute to the evolution of V. cholerae hybrid strains.IMPORTANCE Natural diversification of CTXФ and ctxAB genes certainly influences disease severity and shifting patterns in major etiological agents of cholera, e.g., the overwhelming emergence of hybrid El Tor variants, replacing the prototype El Tor strains of V. cholerae This report, showing the occurrence of CTXET comprising a novel variant of ctxAB in V. mimicus, points out a previously unnoticed evolutionary event that is independent of the evolutionary event associated with the El Tor strains of V. cholerae Identification and cluster analysis of the newly discovered alleles of tcpA and toxT suggest their horizontal transfer from an uncommon clone of V. cholerae The genomic contents of ToxT regulon and of tandemly arranged multiple pre-CTXФEnv and of a CTXФET in V. mimicus probably act as salient raw materials that induce natural recombination among the hallmark virulence genes of hybrid V. cholerae strains. This report provides valuable information to enrich our knowledge on the evolution of new variant CT and ToxT regulons.

Multiplex genome editing by natural transformation in Vibrio mimicus with potential application in attenuated vaccine development.

Vibrio mimicus (V. mimicus) is a significant pathogen in freshwater catfish, though knowledge of virulence determinants and effective vaccine is lacking. Multiplex genome editing by natural transformation (MuGENT) is an easy knockout method, which has successfully used in various bacteria except for V. mimicus. Here, we found V. mimicus strain SCCF01 can uptake exogenous DNA and insert it into genome by natural transformation assay. Subsequently, we exploited this property to make five mutants (△Hem, △TS1, △TS2, △TS1△TS2, and △II), and removed the antibiotic resistance marker by Flp-recombination. Finally, all of the mutants were identified by PCR and RT-PCR. The results showed that combination of natural transformation and FLP-recombination can be applied successfully to generate targeted gene disruptions without the antibiotic resistance marker in V. mimicus. In addition, the five mutants showed mutant could be inherited after several subcultures and a 668-fold decrease in the virulence to yellow catfish (Pelteobagrus fulvidraco). This study provides a convenient method for the genetic manipulation of V. mimicus. It will facilitate the identification and characterization of V. mimicus virulence factors and eventually contribute to a better understanding of V. mimicus pathogenicity and development of attenuated vaccine.

Regulation of Vibrio mimicus metalloprotease (VMP) production by the quorum-sensing master regulatory protein, LuxR.

Vibrio mimicus is an estuarine bacterium, while it can cause severe diarrhea, wound infection, and otitis media in humans. This pathogen secretes a relatively important toxin named V. mimicus metalloprotease (VMP). In this study, we clarified regulation of the VMP production according to the quorum-sensing master regulatory protein named LuxR. First, the full length of luxR gene, encoding LuxR, was detected in V. mimicus strain E-37, an environmental isolate. Next, the putative consensus binding sequence of LuxR protein could be detected in the upstream (promoter) region of VMP encoding gene, vmp. Finally, the effect of disruption of luxR gene on the expression of vmp and production of VMP was evaluated. Namely, the expression of vmp was significantly diminished by luxR disruption and the production of VMP was severely altered. Taken together, here we report that VMP production is under the positive regulation of the quorum-sensing master regulatory protein, LuxR.

Identification of capsule, biofilm, lateral flagellum, and type IV pili in Vibrio mimicus strains.

Vibrio mimicus is a bacterium that causes gastroenteritis; it is closely related to Vibrio cholerae, and can cause acute diarrhea like cholera- or dysentery-type diarrhea. It is distributed worldwide. Factors associated with virulence (such as hemolysins, enterotoxins, proteases, phospholipases, aerobactin, and hemagglutinin) have been identified; however, its pathogenicity mechanism is still unknown. In pathogenic Vibrio species such as V. cholerae, Vibrio. parahaemolyticus and Vibrio vulnificus, capsule, biofilms, lateral flagellum, and type IV pili are structures described as essential for pathogenicity. These structures had not been described in V. mimicus until this work. We used 20 V. mimicus strains isolated from water (6), oyster (9), and fish (5) samples and we were able to identify the capsule, biofilm, lateral flagellum, and type IV pili through phenotypic tests, electron microscopy, PCR, and sequencing. In all tested strains, we observed and identified the presence of capsular exopolysaccharide, biofilm formation in an in vitro model, as well as swarming, multiple flagellation, and pili. In addition, we identified homologous genes to those described in other bacteria of the genus in which these structures have been found. Identification of these structures in V. mimicus is a contribution to the biology of this organism and can help to reveal its pathogenic behavior.

A novel extracellular protease of Vibrio mimicus that mediates maturation of an endogenous hemolysin.

Vibrio mimicus, a human pathogen that causes gastroenteritis, produces an enterotoxic hemolysin as a virulence factor. The hemolysin is secreted extracellularly as an inactive protoxin and converted to a mature toxin through removal of the N-terminal propeptide, which comprises 151 amino acid residues. In this study, a novel protease having the trypsin-like substrate specificity was purified from the bacterial culture supernatant. The N-terminal amino acid sequence of the purified protein was identical with putative trypsin VMD27150 of V. mimicus strain VM573. The purified protease was found to cause maturation of the protoxin by cleavage of the Arg(151)-Ser(152) bond. Deletion of the protease gene resulted in increased amounts of the protoxin in the culture supernatant. In addition, expression of the hemolysin and protease genes was detected during the logarithmic growth phase. These findings indicate that the protease purified may mediate maturation of the hemolysin.

RpoS sigma factor mediates adaptation and virulence in Vibrio mimicus.

The alternative sigma factor RpoS functions as a regulator of stress and virulence response in numerous bacterial species. Vibrio mimicus is a critical opportunistic pathogen causing huge losses to aquaculture. However, the exact role of RpoS in V. mimicus remains unclear. In this study, rpoS deletion mutant of V. mimicus was constructed through allelic exchange and the phenotypic and transcriptional changes were investigated to determine the function of RpoS. The abilities of growth, motility, biofilm production, hemolytic activity and pathogenicity were significantly impaired in ΔrpoS strain. Stationary-phase cells of ΔrpoS strain showed lower tolerance to H2O2, heat, ethanol, and starvation stress than the wild-type strain. Transcriptome analyses revealed the involvement of rpoS in various cellular processes, notably bacterial-type flagellum synthesis and assembly, membrane synthesis and assembly and response to various stimuli. Phenotypic and RNA-seq analysis revealed that RpoS is required for biofilm formation, stress resistance, and pathogenicity in V. mimicus. Furthermore, ß-galactosidase activity showed that rpoS is essential for optimal transcription of the flgK, fliA, cheA, mcpH mRNA. These results offer significant insight into the function and regulatory network of rpoS/RpoS, thereby improving our understanding and facilitating selection of molecular targets for future prevention strategies against V. mimicus.

Non-cholera Vibrio infections in Southeast Asia: A systematic review and meta-analysis.

We reviewed and analyzed the existing data on vibriosis in Southeast Asia to better understand its burden and prevalent causal agents. We searched PubMed, Web of Science, and EMBASE for studies published between January 2000 and April 2024. A random-effects meta-analysis was used to estimate the pooled isolation rate of non-cholera Vibrio species. Among the 1385 retrieved studies, 22 met the inclusion criteria for the systematic review and 11 were included in the meta-analysis. The pooled isolation rate of non-cholera Vibrio species among diarrheal patients was 5.0 %. Most species that caused vibriosis included V. parahaemolyticus, V. mimicus, V. vulnificus, non-O1/non-O139 V. cholerae, V. fluvialis, and V. alginolyticus. Pooled isolation rate of V. parahaemolyticus and non-O1 V. cholerae were 7.0, and 4.0, respectively. The prevalence of vibriosis in Southeast Asia is non-negligible. Public health strategies should prioritize enhanced surveillance, and clinicians should consider vibriosis in diarrheal patients with seafood consumption history.

The cAMP Receptor Protein (CRP) of Vibrio mimicus Regulates Its Bacterial Growth, Type II Secretion System, Flagellum Formation, Adhesion Genes, and Virulence.

Vibrio mimicus is a serious pathogen in aquatic animals, resulting in significant economic losses. The cAMP receptor protein (CRP) often acts as a central regulator in highly pathogenic pathogens. V. mimicus SCCF01 is a highly pathogenic strain isolated from yellow catfish; the crp gene deletion strain (Δcrp) was constructed by natural transformation to determine whether this deletion affects the virulence phenotypes. Their potential molecular connections were revealed by qRT-PCR analysis. Our results showed that the absence of the crp gene resulted in bacterial and colony morphological changes alongside decreases in bacterial growth, hemolytic activity, biofilm formation, enzymatic activity, motility, and cell adhesion. A cell cytotoxicity assay and animal experiments confirmed that crp contributes to V. mimicus pathogenicity, as the LD50 of the Δcrp strain was 73.1-fold lower compared to the WT strain. Moreover, qRT-PCR analysis revealed the inhibition of type II secretion system genes, flagellum genes, adhesion genes, and metalloproteinase genes in the deletion strain. This resulted in the virulence phenotype differences described above. Together, these data demonstrate that the crp gene plays a core regulatory role in V. mimicus virulence and pathogenicity.

Vibriosis in South Asia: A systematic review and meta-analysis.

OBJECTIVES: South Asia remains home to foodborne diseases caused by the Vibrio species. We aimed to compile and update information on the epidemiology of vibriosis in South Asia. METHODS: For this systematic review and meta-analysis, we searched PubMed, Web of Science, EMBASE, and Google Scholar for studies related to vibriosis in South Asia published up to May 2023. A random-effects meta-analysis was used to estimate the pooled isolation rate of non-cholera-causing Vibrio species. RESULTS: In total, 38 studies were included. Seven of these were case reports and 22 were included in the meta-analysis. The reported vibriosis cases were caused by non-O1/non-O139 V. cholerae, V. parahaemolyticus, V. fluvialis, and V. vulnificus. The overall pooled isolation rate was 4.0% (95% confidence interval [CI] 3.0-5.0%) in patients with diarrhea. Heterogeneity was high (I2 = 98.0%). The isolation rate of non-O1/non-O139 V. cholerae, V. parahaemolyticus, and V. fluvialis were 9.0 (95% CI 7.0-10.0%), 1.0 (95% CI 1.0-2.0%), and 2.0 (95% CI: 1.0-3.0%), respectively. Regarding V. parahaemolyticus, O3:K6 was the most frequently isolated serotype. Cases peaked during summer. Several studies reported antibiotic-resistant strains and those harboring extended-spectrum beta-lactamases genes. CONCLUSIONS: This study demonstrates a high burden of infections caused by non-cholera-causing Vibrio species in South Asia.