Current and future perspectives for controlling Vibrio biofilms in the seafood industry: a comprehensive review

Sublethal Curcumin Exposure Induces Global Gene Expression and Biofilm-Related Phenotypic Changes in Vibrio parahaemolyticus

Vibrio parahaemolyticus, a foodborne pathogen found in marine environments, is susceptible to the antimicrobial effects of curcumin-a lipophilic polyphenolic pigment with diverse biological activities. While sublethal doses of curcumin inhibit behaviors of V. parahaemolyticus, the underlying molecular mechanisms remain poorly characterized. In this study, we aimed to investigate the impact of sublethal doses of curcumin on gene expression and key bacterial processes in V. parahaemolyticus. RNA sequencing (RNA-seq) revealed that sublethal curcumin concentrations significantly suppressed bacterial growth and altered the expression of 788 genes. These differentially expressed genes (DEGs) were associated with critical pathways, including upregulated systems such as polar flagellum, type IV pili, and type VI secretion systems (T6SS1 and T6SS2), as well as downregulated systems such as lateral flagella, exopolysaccharides (EPS), and type III secretion systems (T3SS1 and T3SS2). Notably, most DEGs involved in cyclic di-GMP (c-di-GMP) metabolism were downregulated, while putative porin-related genes were upregulated. Additionally, sublethal curcumin significantly inhibited biofilm formation and swimming motility but enhanced c-di-GMP production in V. parahaemolyticus. This study provides valuable insights into how V. parahaemolyticus adjusts its gene expression in response to sublethal levels of curcumin.

Effects of low-salt stress on biological characteristics and transcriptomic profiles of Vibrio parahaemolyticus

Studies have proved that halophilic Vibrio parahaemolyticus is widely detected in freshwater environments (salinity <0.5 %). However, the growth and colonization of V. parahaemolyticus in low-salt environments remain unclear. This study was envisaged to assess the effects of low-salt stress on the growth, motility and biofilm formation of V. parahaemolyticus and the transcriptomic changes that the bacterium responds to such stress. The results indicated that low salt concentrations supported the growth (allowing growth to proceed, though at a lower speed) of V. parahaemolyticus, prolonged the lag time (LT), and decreased the maximum specific growth rate (μmax) of V. parahaemolyticus. Additionally, this low salinity inhibited its motility and enhanced its biofilm formation capacity. Notably, the growth of V. parahaemolyticus on both freshwater and marine-cultured Litopenaeus vannamei exhibited a similar trend, suggesting that V. parahaemolyticus might have adapted to thrive in freshwater food. Furthermore, the reasons for the support of V. parahaemolyticus growth in 0.25 % NaCl was analyzed by transcriptome sequencing (RNA-seq). RNA-seq revealed that V. parahaemolyticus can improve resistance to adverse environments by reducing energy consumption and enhancing oxidative stress resistance to adapt to a low-salt environment. This study revealed that the freshwater environment supported the growth of V. parahaemolyticus and its influence on the growth of V. parahaemolyticus, providing valuable theoretical support for risk assessment.

Exploring the potential of hydrolytic enzymes combined with antibacterial agents to disrupt pathogenic biofilms and disinfect released cells

Biofilms are bacterial communities encapsulated in a self-produced extracellular polymeric matrix comprising carbohydrates, proteins, lipids, and DNA. This matrix provides structural integrity while significantly enhancing bacterial antibiotic resistance, presenting substantial disinfection challenges. The persistence of biofilm-associated infections and foodborne outbreaks underscores the need for more effective disinfection strategies. Conventional antibacterial agents often are less effective against biofilm-protected cells compared to their efficacy against planktonic (non-attached) bacteria. Integrating hydrolytic enzymes, such as cellulases, proteases, and DNases, into disinfection protocols offers a promising approach by breaking down the biofilm matrix to expose the bacteria. However, the follow-up use of antibacterial agents is important, as enzymes alone do not possess bactericidal properties. Unlike traditional disinfectants, natural antibacterial agents work synergistically with enzymes, enhancing biofilm disruption without compromising the enzymatic activity through oxidation. This review offers a comprehensive analysis of the current knowledge and potential of combining hydrolytic enzymes with disinfectants to disrupt biofilms and eradicate the released bacterial cells, emphasizing applications for clinical and foodborne pathogens.

Phenotypic changes and gene expression profiles of Vibrio parahaemolyticus in response to low concentrations of ampicillin

Vibrio parahaemolyticus is a leading cause of seafood-associated gastroenteritis and possesses intrinsic resistance to ampicillin. While ampicillin can trigger transcriptional responses of global genes, the behavioral and molecular changes that occur in V. parahaemolyticus when exposed to ampicillin are not fully understood. In this work, we investigated the effects of low concentrations of ampicillin on the physiology and gene expression of V. parahaemolyticus by combining phenotypic assays and RNA sequencing (RNA-seq) analysis. Our results showed that the growth of V. parahaemolyticus were notably delayed, and both motility and c-di-GMP production were significantly inhibited in the response to low concentrations of ampicillin stress. In contrast, biofilm formation by V. parahaemolyticus was enhanced by exposure to low concentrations of ampicillin. However, low concentrations of ampicillin had no effect on the cytotoxicity or adherence activity of V. parahaemolyticus. The RNA-seq data revealed that a low concentration of ampicillin significantly affected the expression levels of 676 genes, including those involved in antibiotic resistance, virulence, biofilm formation, and regulation. This work contributes to our understanding of how V. parahaemolyticus alters its behavior and gene expression in response to ampicillin exposure.

Assessment of Vibrionaceae prevalence in seafood from Qidong market and analysis of Vibrio parahaemolyticus strains

The aim of this study was to investigate the prevalence of Vibrionaceae family in retail seafood products available in the Qidong market during the summer of 2023 and to characterize Vibrio parahaemolyticus isolates, given that this bacterium is the leading cause of seafood-associated food poisoning. We successfully isolated a total of 240 Vibrionaceae strains from a pool of 718 seafood samples. The breakdown of the isolates included 146 Photobacterium damselae, 59 V. parahaemolyticus, 18 V. campbellii, and 11 V. alginolyticus. Among these, P. damselae and V. parahaemolyticus were the predominant species, with respective prevalence rates of 20.3% and 8.2%. Interestingly, all 59 isolates of V. parahaemolyticus were identified as non-pathogenic. They demonstrated proficiency in swimming and swarming motility and were capable of forming biofilms across a range of temperatures. In terms of antibiotic resistance, the V. parahaemolyticus isolates showed high resistance to ampicillin, intermediate resistance to cefuroxime and cefazolin, and were sensitive to the other antibiotics evaluated. The findings of this study may offer valuable insights and theoretical support for enhancing seafood safety measures in Qidong City.

Isolation, characterization, and application of bacteriophage on Vibrio parahaemolyticus biofilm to control seafood contamination

OBJECTIVE

This study intended to isolate a Vibrio-particular phage from the natural environment, analyse its characteristics and genome sequence, and investigate its reduction effect on V. parahaemolyticus biofilm as a biocontrol agent in squid and mackerel.

METHODS

Among 21 phages, phage CAU_VPP01, isolated from beach mud, was chosen for further experiments based on host range and EOP tests. When examining the reduction effect of phage CAU_VPP01 against Vibrio parahaemolyticus biofilms on surfaces (stainless steel [SS] and polyethylene terephthalate [PET]) and food surfaces (squid and mackerel).

RESULTS

The phage showed the most excellent reduction effect at a multiplicity-of-infection (MOI) 10. Three-dimensional images acquired with confocal laser scanning microscopy (CLSM) analysis were quantified using COMSTAT, which showed that biomass, average thickness, and roughness coefficient decreased when treated with the phage. Colour and texture analysis confirmed that the quality of squid and mackerel was maintained after the phage treatment. Finally, a comparison of gene expression levels determined by qRT-PCR analysis showed that the phage treatment induced a decrease in the gene expression of flaA, vp0962, andluxS, as examples.

CONCLUSION

This study indicated that Vibrio-specific phage CAU_VPP01 effectively controlled V. parahaemolyticus biofilms under various conditions and confirmed that the isolated phage could possibly be used as an effective biocontrol weapon in the seafood manufacturing industry.

Environmental magnesium ion affects global gene expression, motility, biofilm formation and virulence of Vibrio parahaemolyticus

Vibrio parahaemolyticus is widely distributed in marine ecosystems. Magnesium ion (Mg2+) is the second most abundant metal cation in seawater, and plays important roles in the growth and gene expression of V. parahaemolyticus, but lacks the detailed mechanisms. In this study, the RNA sequencing data demonstrated that a total of 1494 genes was significantly regulated by Mg2+. The majority of the genes associated with lateral flagella, exopolysaccharide, type III secretion system 2, type VI secretion system (T6SS) 1, T6SS2, and thermostable direct hemolysin were downregulated. A total of 18 genes that may be involved in c-di-GMP metabolism and more than 80 genes encoding putative regulators were also significantly and differentially expressed in response to Mg2+, indicating that the adaptation process to Mg2+ stress may be strictly regulated by complex regulatory networks. In addition, Mg2+ promoted the proliferative speed, swimming motility and cell adhesion of V. parahaemolyticus, but inhibited the swarming motility, biofilm formation, and c-di-GMP production. However, Mg2+ had no effect on the production of capsular polysaccharide and cytoxicity against HeLa cells. Therefore, Mg2+ had a comprehensive impact on the physiology and gene expression of V. parahaemolyticus.

Partial Characterization of Three Bacteriophages Isolated from Aquaculture Hatchery Water and Their Potential in the Biocontrol of Vibrio spp

Bacteriophages are currently considered one of the most promising alternatives to antibiotics under the 'One Health' approach due to their ability to effectively combat bacterial infections. This study aimed to characterize Vibrio species in hatchery water samples collected from an aquaculture farm and investigate the biocontrol potential of their bacteriophages. Vibrio spp. (n = 32) isolates confirmed by LNA probe-based qPCR were used as hosts. Three Vibrio phages were isolated. IKEM_vK exhibited a broad host range, infecting V. harveyi (n = 8), V. alginolyticus (n = 2), V. azureus (n = 1), and V. ordalii (n = 1). IKEM_v5 showed lytic activity against V. anguillarum (n = 4) and V. ordalii (n = 1), while IKEM_v14 was specific to V. scophtalmi (n = 4). The morphological appearance of phages and their lytic effects on the host were visualized using scanning electron microscopy (SEM). All three phages remained relatively stable within the pH range of 6-11 and up to 60 °C. The lytic activities and biofilm inhibition capabilities of these phages against planktonic Vibrio cells support their potential applications in controlling vibriosis in aquaculture systems.

Vibrio fischeri: a model for host-associated biofilm formation

Multicellular communities of adherent bacteria known as biofilms are often detrimental in the context of a human host, making it important to study their formation and dispersal, especially in animal models. One such model is the symbiosis between the squid Euprymna scolopes and the bacterium Vibrio fischeri. Juvenile squid hatch aposymbiotically and selectively acquire their symbiont from natural seawater containing diverse environmental microbes. Successful pairing is facilitated by ciliary movements that direct bacteria to quiet zones on the surface of the squid's symbiotic light organ where V. fischeri forms a small aggregate or biofilm. Subsequently, the bacteria disperse from that aggregate to enter the organ, ultimately reaching and colonizing deep crypt spaces. Although transient, aggregate formation is critical for optimal colonization and is tightly controlled. In vitro studies have identified a variety of polysaccharides and proteins that comprise the extracellular matrix. Some of the most well-characterized matrix factors include the symbiosis polysaccharide (SYP), cellulose polysaccharide, and LapV adhesin. In this review, we discuss these components, their regulation, and other less understood V. fischeri biofilm contributors. We also highlight what is currently known about dispersal from these aggregates and host cues that may promote it. Finally, we briefly describe discoveries gleaned from the study of other V. fischeri isolates. By unraveling the complexities involved in V. fischeri's control over matrix components, we may begin to understand how the host environment triggers transient biofilm formation and dispersal to promote this unique symbiotic relationship.

Benzalkonium chloride disinfectant residues stimulate biofilm formation and increase survival of Vibrio bacterial pathogens

Vibrio spp. are opportunistic human and animal pathogens found ubiquitously in marine environments. Globally, there is a predicted rise in the prevalence of Vibrio spp. due to increasing ocean temperatures, which carries significant implications for public health and the seafood industry. Consequently, there is an urgent need for enhanced strategies to control Vibrio spp. and prevent contamination, particularly in aquaculture and seafood processing facilities. Presently, these industries employ various disinfectants, including benzalkonium chloride (BAC), as part of their management strategies. While higher concentrations of BAC may be effective against these pathogens, inadequate rinsing post-disinfection could result in residual concentrations of BAC in the surrounding environment. This study aimed to investigate the adaptation and survival of Vibrio spp. exposed to varying concentrations of BAC residues. Results revealed that Vibrio bacteria, when exposed, exhibited a phenotypic adaptation characterized by an increase in biofilm biomass. Importantly, this effect was found to be strain-specific rather than species-specific. Exposure to BAC residues induced physiological changes in Vibrio biofilms, leading to an increase in the number of injured and alive cells within the biofilm. The exact nature of the "injured" bacteria remains unclear, but it is postulated that BAC might heighten the risk of viable but non-culturable (VBNC) bacteria development. These VBNC bacteria pose a significant threat, especially since they cannot be detected using the standard culture-based methods commonly employed for microbiological risk assessment in aquaculture and seafood industries. The undetected presence of VBNC bacteria could result in recurrent contamination events and subsequent disease outbreaks. This study provides evidence regarding the role of c-di-GMP signaling pathways in Vibrio adaptation mechanisms and suggests that c-di-GMP mediated repression is a potential avenue for further research. The findings underscore that the misuse and overuse of BAC may increase the risk of biofilm development and bacterial survival within the seafood processing chain.

Targeted phytogenic compounds against Vibrio parahaemolyticus biofilms

As one of main culprit of seafood-associated human illness, Vibrio parahaemolyticus can readily accumulate on biotic or abiotic surfaces to form biofilms in the seafood processing environment. Biofilm formation on various surfaces can provide a protective barrier for viable bacterial cells that are resistant to most traditional bacteriostatic measures. This underscores the necessity and urgency of developing effective alternative strategies to control V. parahaemolyticus biofilms. Plants have always provided an extensive and infinite source of biologically active compounds for "green" antibiofilm agents. This review summarizes recent developments in promising multitargeted phytogenic compounds against V. parahaemolyticus biofilms. This review provides valuable insights into potential research targets that can be pursued further to identify potent natural antibiofilm agents in the food industry.

Insights into the mechanisms and key factors influencing biofilm formation by Aeromonas hydrophila in the food industry: A comprehensive review and bibliometric analysis

Biofilm formation by Aeromonas hydrophila in the food industry poses significant challenges to food safety and quality. Therefore, this comprehensive review aimed to provide insights into the mechanisms and key factors influencing A. hydrophila biofilm formation. It explores the molecular processes involved in initial attachment, microcolony formation, and biofilm maturation; moreover, it concurrently examines the impact of intrinsic factors, including quorum sensing, cyclic-di-GMP, the efflux pump, and antibiotic resistance, as well as environmental conditions, such as temperature, nutrient availability, and osmotic pressure, on biofilm architecture and resilience. Furthermore, the article highlights the potential of bibliometric analysis as a promising method for conceptualizing the research landscape of and identifying knowledge gaps in A. hydrophila biofilm research. The findings underscore the requirement for focused interventions that prevent biofilm development and raise food sector safety. The consolidation of current information and incorporation of bibliometric analysis enhances existing understanding of A. hydrophila biofilm formation and offers insights for future research and control strategies within a food industry context.

Sources and contamination routes of seafood with human pathogenic Vibrio spp.: A Farm-to-Fork approach

Vibrio spp., known human foodborne pathogens, thrive in freshwater, estuaries, and marine settings, causing vibriosis upon ingestion. The rising global vibriosis cases due to climate change necessitate a deeper understanding of Vibrio epidemiology and human transmission. This review delves into Vibrio contamination in seafood, scrutinizing its sources and pathways. We comprehensively assess the contamination of human-pathogenic Vibrio in the seafood chain, covering raw materials to processed products. A "Farm-to-Fork" approach, aligned with the One Health concept, is essential for grasping the complex nature of Vibrio contamination. Vibrio's widespread presence in natural and farmed aquatic environments establishes them as potential entry points into the seafood chain. Environmental factors, including climate, human activities, and wildlife, influence contamination sources and routes, underscoring the need to understand the origin and transmission of pathogens in raw seafood. Once within the seafood chain, the formation of protective biofilms on various surfaces in production and processing poses significant food safety risks, necessitating proper cleaning and disinfection to prevent microbial residue. In addition, inadequate seafood handling, from inappropriate processing procedures to cross-contamination via pests or seafood handlers, significantly contributes to Vibrio food contamination, thus warranting attention to reduce risks. Information presented here support the imperative for proactive measures, robust research, and interdisciplinary collaboration in order to effectively mitigate the risks posed by human pathogenic Vibrio contamination, safeguarding public health and global food security. This review serves as a crucial resource for researchers, industrials, and policymakers, equipping them with the knowledge to develop biosecurity measures associated with Vibrio-contaminated seafood.

Bioactive ZnO Nanoparticles: Biosynthesis, Characterization and Potential Antimicrobial Applications

In recent years, biosynthesized zinc oxide nanoparticles (ZnONPs) have gained tremendous attention because of their safe and non-toxic nature and distinctive biomedical applications. A diverse range of microbes (bacteria, fungi and yeast) and various parts (leaf, root, fruit, flower, peel, stem, etc.) of plants have been exploited for the facile, rapid, cost-effective and non-toxic synthesis of ZnONPs. Plant extracts, microbial biomass or culture supernatant contain various biomolecules including enzymes, amino acids, proteins, vitamins, alkaloids, flavonoids, etc., which serve as reducing, capping and stabilizing agents during the biosynthesis of ZnONPs. The biosynthesized ZnONPs are generally characterized using UV-VIS spectroscopy, TEM, SEM, EDX, XRD, FTIR, etc. Antibiotic resistance is a serious problem for global public health. Due to mutation, shifting environmental circumstances and excessive drug use, the number of multidrug-resistant pathogenic microbes is continuously rising. To solve this issue, novel, safe and effective antimicrobial agents are needed urgently. Biosynthesized ZnONPs could be novel and effective antimicrobial agents because of their safe and non-toxic nature and powerful antimicrobial characteristics. It is proven that biosynthesized ZnONPs have strong antimicrobial activity against various pathogenic microorganisms including multidrug-resistant bacteria. The possible antimicrobial mechanisms of ZnONPs are the generation of reactive oxygen species, physical interactions, disruption of the cell walls and cell membranes, damage to DNA, enzyme inactivation, protein denaturation, ribosomal destabilization and mitochondrial dysfunction. In this review, the biosynthesis of ZnONPs using microbes and plants and their characterization have been reviewed comprehensively. Also, the antimicrobial applications and mechanisms of biosynthesized ZnONPs against various pathogenic microorganisms have been highlighted.

Transcriptomic Profiles of Vibrio parahaemolyticus During Biofilm Formation

Vibrio parahaemolyticus, the leading cause of bacterial seafood-associated gastroenteritis, can form biofilms. In this work, the gene expression profiles of V. parahaemolyticus during biofilm formation were investigated by transcriptome sequencing. A total of 183, 503, and 729 genes were significantly differentially expressed in the bacterial cells at 12, 24 and 48 h, respectively, compared with that at 6 h. Of these, 92 genes were consistently activated or repressed from 6 to 48 h. The genes involved in polar flagellum, chemotaxis, mannose-sensitive haemagglutinin type IV pili, capsular polysaccharide, type III secretion system 1 (T3SS1), T3SS2, thermostable direct hemolysin (TDH), type VI secretion system 1 (T6SS1) and T6SS2 were downregulated, whereas those involved in V. parahaemolyticus pathogenicity island (Vp-PAI) (except for T3SS2 and TDH) and membrane fusion proteins were upregulated. Three extracellular protease genes (vppC, prtA and VPA1071) and a dozen of outer membrane protein encoding genes were also significantly differentially expressed during biofilm formation. In addition, five putative c-di-GMP metabolism-associated genes were significantly differentially expressed, which may account for the drop in c-di-GMP levels after the beginning of biofilm formation. Moreover, many putative regulatory genes were significantly differentially expressed, and more than 1000 putative small non-coding RNAs were detected, suggesting that biofilm formation was tightly regulated by complex regulatory networks. The data provided a global view of gene expression profiles during biofilm formation, showing that the significantly differentially expressed genes were involved in multiple cellular pathways, including virulence, biofilm formation, metabolism, and regulation.

Trend of Pathogenic Vibrio parahaemolyticus Occurrences in Bivalve Molluscs Harvested in Sardinian Coastal Environments Between 2011 and 2018

The aim of the present study was to evaluate Vibrio parahaemolyticus occurrences in bivalve molluscs harvested from Sardinian coastal environments between 2013 and 2015. The prevalence of pathogenic V. parahaemolyticus isolates is based on the detection of the two major virulence genes thermostable direct hemolysin (tdh) and thermolabile hemolysin (trh) To assess changes between 2011 and 2018 in the prevalence of V. parahaemolyticus in bivalve molluscs, we compared our results with those of previous investigations. In total, 2,933 samples were collected: 1,079 in 2013, 1,288 in 2014, and 566 in 2015. The mean prevalence of V. parahaemolyticus in shellfish was 3.5% in 2013, 1.7% in 2014, and 3.5% in 2015. The highest percentage of positive samples in 2013 and 2014 was observed in clams (3.5% and 2.7%, respectively), whereas in 2015, it was reported in oysters (15.1%). By comparing the sampling period of 2011-2014 with that of 2015-2018, an increase in the prevalence of V. parahaemolyticus was observed in shellfish (p < 0.05). In parallel, 208 potentially enteropathogenic V. parahaemolyticus strains were identified through the years 2011-2018 and, in particular, 10 trh+ and six tdh+ isolates. Our present study provides information regarding trends of V. parahaemolyticus occurrences in bivalve molluscs harvested from Sardinian coastal environments between 2011 and 2018 suggesting that the prevalence varies depending on the sampling period and shellfish species.

Antibiofilm mechanism of peppermint essential oil to avert biofilm developed by foodborne and food spoilage pathogens on food contact surfaces

Establishing efficient methods to combat bacterial biofilms is a major concern. Natural compounds, such as essential oils derived from plants, are among the favored and recommended strategies for combatting bacteria and their biofilm. Therefore, we evaluated the antibiofilm properties of peppermint oil as well as the activities by which it kills bacteria generally and particularly their biofilms. Peppermint oil antagonistic activities were investigated against Vibrio parahaemolyticus, Listeria monocytogenes, Pseudomonas aeruginosa, Escherichia coli O157:H7, and Salmonella Typhimurium on four food contact surfaces (stainless steel, rubber, high-density polyethylene, and polyethylene terephthalate). Biofilm formation on each studied surface, hydrophobicity, autoaggregation, metabolic activity, and adenosine triphosphate quantification were evaluated for each bacterium in the presence and absence (control) of peppermint oil. Real-time polymerase chain reaction, confocal laser scanning microscopy, and field-emission scanning electron microscopy were utilized to analyze the effects of peppermint oil treatment on the bacteria and their biofilm. Results showed that peppermint oil (1/2× minimum inhibitory concentration [MIC], MIC, and 2× MIC) substantially lessened biofilm formation, with high bactericidal properties. A minimum of 2.5-log to a maximum of around 5-log reduction was attained, with the highest sensitivity shown by V. parahaemolyticus. Morphological experiments revealed degradation of the biofilm structure, followed by some dead cells with broken membranes. Thus, this study established the possibility of using peppermint oil to combat key foodborne and food spoilage pathogens in the food processing environment.

Characterization of ready-to-eat fish surface as a potential source of contamination of Vibrio parahaemolyticus biofilms

The worldwide consumption of ready-to-eat seafood products has steadily increased due to a range of health benefits. However, depending on the handling or cutting process of raw fish, ready-to-eat sashimi can be exposed to microbiological risks that can lead to foodborne infection by marine pathogens. Since surface characteristics are key factors for microbial adhesion and biofilm formation, the present study aims to determine the correlation between raw fish skin properties and Vibrio parahaemolyticus biofilm formation. We analyzed V. parahaemolyticus biofilms (ATCC 17802; initially inoculated ca. 2 or 4 log CFU/cm²) on fish skin (gizzard shad, pomfret, red snapper, and mackerel; fish species served as sashimi without peeling the skin) formed under simulated marine environments (incubating in artificial seawater with rocking motion at 30 °C, the maximum temperature of seasonal seawater) for 24 h. The characteristics of fish skin were determined using confocal laser scanning microscopy/scanning electron microscopy. V. parahaemolyticus showed higher biofilm counts on fish skins than on stainless steel, which was used as a control (P < 0.05). In particular, V. parahaemolyticus formed biofilms with significantly higher levels of bacterial populations on gizzard shad and pomfret (ca. 5 log CFU/cm²; P < 0.05), highlighting the relationship between the biofilm formation level and the characteristics of gizzard shad and pomfret skins. The surface roughness of fish skins, including the main roughness parameters (Ra, Rq, and Rz), influenced the attachment of V. parahaemolyticus (P < 0.05). Additionally, images of V. parahaemolyticus biofilms suggested that different topographical profiles of fish species (e.g., mucus, unique structural features, etc.) could cause V. parahaemolyticus to exhibit different biofilm phenotypes, such as sticking to or entangling on the fish skin surface. The major findings of this study provide various phenotypic adhesions of V. parahaemolyticus to fish skin in considerations of the potential hazard for the consumption of ready-to-eat sashimi served with its skin.

Current and future interventions for improving poultry health and poultry food safety and security: A comprehensive review

Poultry is thriving across the globe. Chicken meat is the most preferred poultry worldwide, and its popularity is increasing. However, poultry also threatens human hygiene, especially as a fomite of infectious diseases caused by the major foodborne pathogens (Campylobacter, Salmonella, and Listeria). Preventing pathogenic bacterial biofilm is crucial in the chicken industry due to increasing food safety hazards caused by recurring contamination and the rapid degradation of meat, as well as the increased resistance of bacteria to cleaning and disinfection procedures commonly used in chicken processing plants. To address this, various innovative and promising strategies to combat bacterial resistance and biofilm are emerging to improve food safety and quality and extend shelf-life. In particular, natural compounds are attractive because of their potential antimicrobial activities. Natural compounds can also boost the immune system and improve poultry health and performance. In addition to phytochemicals, bacteriophages, nanoparticles, coatings, enzymes, and probiotics represent unique and environmentally friendly strategies in the poultry processing industry to prevent foodborne pathogens from reaching the consumer. Lactoferrin, bacteriocin, antimicrobial peptides, cell-free supernatants, and biosurfactants are also of considerable interest for their prospective application as natural antimicrobials for improving the safety of raw poultry meat. This review aims to describe the feasibility of these proposed strategies and provide an overview of recent published evidences to control microorganisms in the poultry industry, considering the human health, food safety, and economic aspects of poultry production.

QsvR and OpaR coordinately repress biofilm formation by Vibrio parahaemolyticus

Mature biofilm formation by Vibrio parahaemolyticus requires exopolysaccharide (EPS), type IV pili, and capsular polysaccharide (CPS). Production of each is strictly regulated by various control pathways including quorum sensing (QS) and bis-(3'-5')-cyclic di-GMP (c-di-GMP). QsvR, an AraC-type regulator, integrates into the QS regulatory cascade via direct control of the transcription of the master QS regulators, AphA and OpaR. Deletion of qsvR in wild-type or opaR mutant backgrounds altered the biofilm formation by V. parahaemolyticus, suggesting that QsvR may coordinate with OpaR to control biofilm formation. Herein, we demonstrated both QsvR and OpaR repressed biofilm-associated phenotypes, c-di-GMP metabolism, and the formation of V. parahaemolyticus translucent (TR) colonies. QsvR restored the biofilm-associated phenotypic changes caused by opaR mutation, and vice versa. In addition, QsvR and OpaR worked coordinately to regulate the transcription of EPS-associated genes, type IV pili genes, CPS genes and c-di-GMP metabolism-related genes. These results demonstrated how QsvR works with the QS system to regulate biofilm formation by precisely controlling the transcription of multiple biofilm formation-associated genes in V. parahaemolyticus.

Quorum sensing and QsvR tightly control the transcription of vpa0607 encoding an active RNase II-type protein in Vibrio parahaemolyticus

Vibrio parahaemolyticus, a Gram-negative, halophilic bacterium, is a leading cause of acute gastroenteritis in humans. AphA and OpaR are the master quorum sensing (QS) regulators operating at low cell density (LCD) and high cell density (HCD), respectively. QsvR is an AraC-type protein that integrates into the QS system to control gene expression by directly controlling the transcription of aphA and opaR. However, the regulation of QsvR itself remains unclear to date. In this study, we show that vpa0607 and qsvR are transcribed as an operon, vpa0607-qsvR. AphA indirectly activates the transcription of vpa0607 at LCD, whereas OpaR and QsvR directly repress vpa0607 transcription at HCD, leading to the highest expression levels of vpa0607 occurs at LCD. Moreover, VPA0607 acts as an active RNase II-type protein in V. parahaemolyticus and feedback inhibits the expression of QsvR at the post-transcriptional level. Taken together, this work deepens our understanding of the regulation of QsvR and enriches the integration mechanisms of QsvR with the QS system in V. parahaemolyticus.

Biofilm formation of pathogenic bacteria isolated from aquatic animals

Bacterial biofilm formation is one of the dynamic processes, which facilitates bacteria cells to attach to a surface and accumulate as a colony. With the help of biofilm formation, pathogenic bacteria can survive by adapting to their external environment. These bacterial colonies have several resistance properties with a higher survival rate in the environment. Especially, pathogenic bacteria can grow as biofilms and can be protected from antimicrobial compounds and other substances. In aquaculture, biofilm formation by pathogenic bacteria has emerged with an increased infection rate in aquatic animals. Studies show that Vibrio anguillarum, V. parahaemolyticus, V. alginolyticus, V. harveyi, V. campbellii, V. fischeri, Aeromonas hydrophila, A. salmonicida, Yersinia ruckeri, Flavobacterium columnare, F. psychrophilum, Piscirickettsia salmonis, Edwardsiella tarda, E. ictaluri, E. piscicida, Streptococcus parauberis, and S. iniae can survive in the environment by transforming their planktonic form to biofilm form. Therefore, the present review was intended to highlight the principles behind biofilm formation, major biofilm-forming pathogenic bacteria found in aquaculture systems, gene expression of those bacterial biofilms and possible controlling methods. In addition, the possibility of these pathogenic bacteria can be a serious threat to aquaculture systems.

Vibrio parahaemolyticus Isolates from Asian Green Mussel: Molecular Characteristics, Virulence and Their Inhibition by Chitooligosaccharide-Tea Polyphenol Conjugates

Fifty isolates of Vibrio parahaemolyticus were tested for pathogenicity, biofilm formation, motility, and antibiotic resistance. Antimicrobial activity of chitooligosaccharide (COS)-tea polyphenol conjugates against all isolates was also studied. Forty-three isolates were randomly selected from 520 isolates from Asian green mussel (Perna viridis) grown on CHROMagarTM Vibrio agar plate. Six isolates were acquired from stool specimens of diarrhea patients. One laboratory strain was V. parahaemolyticus PSU.SCB.16S.14. Among all isolates tested, 12% of V. parahaemolyticus carried the tdh+trh- gene and were positive toward Kanagawa phenomenon test. All of V. parahaemolyticus isolates could produce biofilm and showed relatively strong motile ability. When COS-catechin conjugate (COS-CAT) and COS-epigallocatechin-3-gallate conjugate (COS-EGCG) were examined for their inhibitory effect against V. parahaemolyticus, the former showed the higher bactericidal activity with the MBC value of 1.024 mg/mL against both pathogenic and non-pathogenic strains. Most of the representative Asian green mussel V. parahaemolyticus isolates exhibited high sensitivity to all antibiotics, whereas one isolate showed the intermediate resistance to cefuroxime. However, the representative clinical isolates were highly resistant to nine types of antibiotics and had multiple antibiotic resistance (MAR) index of 0.64. Thus, COS-CAT could be used as potential antimicrobial agent for controlling V. parahaemolyticus-causing disease in Asian green mussel.

Complex regulatory networks of virulence factors in Vibrio vulnificus

The fulminating zoonotic pathogen Vibrio vulnificus is the causative agent of fatal septicemia in humans and fish, raising tremendous economic burdens in healthcare and the aquaculture industry. V. vulnificus exploits various virulence factors, including biofilm-related factors and exotoxins, for its persistence in nature and pathogenesis during infection. Substantial studies have found that the expression of virulence factors is coordinately regulated by numerous transcription factors that recognize the changing environments. Here, we summarize and discuss the recent discoveries of the physiological roles of virulence factors in V. vulnificus and their regulation by transcription factors in response to various environmental signals. This expanded understanding of molecular pathogenesis would provide novel clues to develop an effective antivirulence therapy against V. vulnificus infection.

Characterization of Vibrio parahaemolyticus isolated from stool specimens of diarrhea patients in Nantong, Jiangsu, China during 2018–2020

Vibrio parahaemolyticus is the leading cause of acute seafood-associated gastroenteritis worldwide. The aim of this study was to investigate the presence of virulence genes, biofilm formation, motor capacities and antimicrobial resistance profile of V. parahaemolyticus isolates isolated from clinical samples in Nantong during 2018–2020. Sixty-six V. parahaemolyticus strains isolated from stool specimens of diarrheal patients were examined. The PCR results showed that there were two tdh+trh+ isolates, four tdh-trh- isolates and sixty tdh+trh- isolates, accounting for 3.0%, 6.1% and 90.9%, respectively. All the tdh carrying isolates manifested the positive reactions for the Kanagawa phenomenon (KP) test. Most of the isolates harbored at least one of the specific DNA markers of ‘pandemic group’ strains, suggesting that the dominant isolates of V. parahaemolyticus in Nantong might belong to the new O3: K6 or its serovariants. All tdh+ isolates possessed the Vp-PAI genes, but no tdh-trh- isolates carried the T3SS2 genes. All isolates were biofilm producers and had relatively strong motor capacities. In addition, the V. parahaemolyticus isolates were resistant to ampicillin (98.5%), cefuroxime (75.6%), cefepime (66.7%), piperacillin (59.1%) and ampicillin/sulbactam (50.0%), but sensitive to ciprofloxacin (100.0%), levofloxacin (100.0%), trimethoprim-sulfamethoxazole (98.5%), gentamicin (98.5%), amikacin (97%), meropenem (71.2%), and ceftazidime (56.1%). Multidrug-resistant isolates in clinical might be related to the inappropriate use of antimicrobials in aquaculture.

Effects of intestinal microbiota on physiological metabolism and pathogenicity of Vibrio

Vibrio species are disseminated broadly in the marine environment. Some of them can cause severe gastroenteritis by contaminating seafood and drinking water, such as Vibrio parahaemolyticus, Vibrio cholerae, and Vibrio vulnificus. However, their pathogenic mechanism still needs to be revealed to prevent and reduce morbidity. This review comprehensively introduces and discusses the common pathogenic process of Vibrio including adhesion, cell colonization and proliferation, and resistance to host immunity. Vibrio usually produces pathogenic factors including hemolysin, type-III secretion system, and adhesion proteins. Quorum sensing, a cell molecular communication system between the bacterial cells, plays an important role in Vibrio intestinal invasion and colonization. The human immune system can limit the virulence of Vibrio or even kill the bacteria through different responses. The intestinal microbiota is a key component of the immune system, but information on its effects on physiological metabolism and pathogenicity of Vibrio is seldom available. In this review, the effects of intestinal microorganisms and their metabolites on the invasion and colonization of common pathogenic Vibrio and VBNC status cells are discussed, which is conducive to finding the next-generation prebiotics. The strategy of dietary intervention is discussed for food safety control. Finally, future perspectives are proposed to prevent Vibrio infection in aquaculture.

Dual-Stage Blue-Light-Guided Membrane and DNA-Targeted Photodynamic Inactivation Using Octyl Gallate for Ultraefficient Eradication of Planktonic Bacteria and Sessile Biofilms

This study aimed to investigate the synergistic bactericidal activity and mechanism of dual-stage light-guided membrane and DNA-targeted photodynamic inactivation (PDI) by the combination of blue light (BL, 420 nm) and the food additive octyl gallate (OG) against Vibrio parahaemolyticus in planktonic and biofilm growth modes. While OG serves as an outstanding exogenous photosensitizer, the planktonic cells were not visibly detectable after the OG-mediated PDI treatment with 0.2 mM OG within 15 min (191.7 J/cm²), and its biofilm was nearly eradicated within 60 min (383.4 J/cm²). Gram-positive Staphylococcus aureus was more susceptible to the PDI than Gram-negative V. parahaemolyticus. The cellular wall and proteins, as well as DNA, were the vulnerable targets for PDI. The membrane integrity could be initially disrupted by OG bearing a hydrophilic head and a hydrophobic tail via transmembrane insertion. The enhancement of OG uptake due to the first-stage light-assisted photochemical internalization (PCI) promoted the accumulation of OG in cells. It further boosted the second-stage light irradiation of the photosensitizer-inducing massive cell death. Upon the second-stage BL irradiation, reactive oxygen species (ROS) generated through the OG-mediated PDI in situ could extensively deconstruct membranes, proteins, and DNA, as well as biofilms, while OG could be activated by BL to carry out photochemical reactions involving the formation of OG-bacterial membrane protein (BMP) covalent conjugates and the interactions with DNA. This dual-stage light-guided subcellular dual-targeted PDI strategy exhibits encouraging effects on the eradication of planktonic bacteria and sessile biofilms, which provides a new insight into the development of an ultraeffective antimicrobial and biofilm removing/reducing technique to improve microbiological safety in the food industry.

A Polysaccharide Biosynthesis Locus in Vibrio parahaemolyticus Important for Biofilm Formation Has Homologs Widely Distributed in Aquatic Bacteria Mainly from Gammaproteobacteria

Vibrio parahaemolyticus is a seafood-borne pathogen that poses a great threat to public health worldwide. It is found in either a planktonic cell or a biofilm form in the natural environment. The cps locus has been the only extensively studied polysaccharide biosynthesis gene cluster involved in biofilm formation for this bacterium. In this study, we found that an additional polysaccharide biosynthesis locus, scv, is also necessary for biofilm maturation. The scv locus is composed of two operons, and a loss of their expression leads to a defective biofilm phenotype. The transcription of the scv locus is under the control of a sigma 54-dependent response regulator, ScvE. In contrast, the quorum-sensing regulator AphA stimulates the expression of the cps locus and the scvABCD operon found in the scv locus. Bioinformatic analyses demonstrated that scv loci are divergent and widely distributed among 28 genera, including 26 belonging to the Gammaproteobacteria and 2 within the Alphaproteobacteria. We also determined that all scv locus-positive species are water-dwelling. Some strains of Aeromonas, Aliivibrio salmonicida, Pseudomonas anguilliseptica, Vibrio breoganii, and Vibrio scophthalmi probably acquired scv loci through insertion sequences and/or integrase-mediated horizontal gene transfer. Gene duplication and fusion were also detected in some scv homologs. Together, our results suggest that the genome of V. parahaemolyticus harbors two distinct polysaccharide biosynthesis loci, which may play a role in fine-tuning biofilm development, and that scv loci likely evolved by horizontal gene transfer, gene loss, gene duplication, and fragment fusion. IMPORTANCE Polysaccharides are the major component of biofilms, which provide survival advantages for bacteria in aquatic environments. The seafood-borne pathogen V. parahaemolyticus possesses a functionally uncharacterized polysaccharide biosynthesis locus, scv. We demonstrated that the scv locus is important for biofilm maturation and that scv expression is positively regulated by ScvE. Strains from 148 aquatic bacterial species possess scv homolog loci. These bacterial species belong to 28 genera, most of which belong to the Gammaproteobacteria class. The evolution and diversification of scv loci are likely driven by horizontal gene transfer, gene loss, gene duplication, and fragment fusion. Our results provide new insights into the function and evolution of this widespread polysaccharide biosynthesis locus.

The Effect of Salinity on Biofilm Formation and c-di-GMP Production in Vibrio parahaemolyticus

Vibrio parahaemolyticus is a moderately halophilic, salt-requiring organism that exhibits optimal growth at approximately 3% salt. Thus, salinity stress is one of the most important stimuli during its lifecycle. The bacterium possesses a strong ability to form biofilms on surfaces, which are thought to be involved in protecting it from adverse environmental conditions. In the present study, salinity-dependent biofilm formation by V. parahaemolyticus was investigated by combining crystal violet staining, colony morphology, intracellular c-di-GMP quantification and quantitative PCR. The results showed that biofilm formation by V. parahaemolyticus was significantly enhanced in low salinity growth conditions and was affected by incubation time. In addition, low salinity reduced intracellular c-di-GMP degradation in V. parahaemolyticus. Transcription of genes encoding ScrABC and ScrG proteins, which are involved in intracellular c-di-GMP metabolism, was inhibited by low salinity growth conditions. Thus, reduced intracellular c-di-GMP degradation in V. parahaemolyticus in low salinity growth conditions may be mediated by repression of scrG and scrABC transcription. Taken together, these results demonstrated for the first time that salinity regulates biofilm formation and c-di-GMP production in V. parahaemolyticus.

Molecular and pathogenic characterization of Vibrio parahaemolyticus isolated from seafood

Gastroenteritis infections in humans are mainly associated with consumption of Vibrio parahaemolyticus contaminated shellfish, which causes health and economic loss. Virulence factor production, antibiotic resistance profile, and biofilm-forming capacity of Vibrio parahaemolyticus isolates on food and food contact surfaces at 30 °C were investigated to evaluate the antibiotic sensitivity and pathogenic level. Strains of V. parahaemolyticus were isolated from shellfish (e.g., Crassostrea gigas, Venerupis philippinarum, Mytilus coruscus, Anadara kagoshimensis) in Korea. When examined for 17 virulence factor-encoding genes, 53.3, 73.1, 87.1, 87.9, and 90.9% of the isolates were positive for genes encoding TDH, T6SS, T3SS1, T3SS2, and Type I pilus, respectively. All isolates showed resistance to vancomycin, tetracyclines, penicillin, nalidixic acid, and doxycycline, among 26 antibiotics tested, with most isolates resistant to kanamycin (93.5%), ampicillin (96.8%), clindamycin (96.8%), tobramycin (88.7%), amikacin (83.97%), and minocycline (80.7%). Biofilm formation, cell-cell attachment, and motility were high in most isolates. These findings may assist in monitoring the epidemics of the pathogen. Continuous monitoring could help to decrease V. parahaemolyticus infections and improve seafood safety.

Promising strategies to control persistent enemies: Some new technologies to combat biofilm in the food industry-A review

Biofilm is an advanced form of protection that allows bacterial cells to withstand adverse environmental conditions. The complex structure of biofilm results from genetic-related mechanisms besides other factors such as bacterial morphology or substratum properties. Inhibition of biofilm formation of harmful bacteria (spoilage and pathogenic bacteria) is a critical task in the food industry because of the enhanced resistance of biofilm bacteria to stress, such as cleaning and disinfection methods traditionally used in food processing plants, and the increased food safety risks threatening consumer health caused by recurrent contamination and rapid deterioration of food by biofilm cells. Therefore, it is urgent to find methods and strategies for effectively combating bacterial biofilm formation and eradicating mature biofilms. Innovative and promising approaches to control bacteria and their biofilms are emerging. These new approaches range from methods based on natural ingredients to the use of nanoparticles. This literature review aims to describe the efficacy of these strategies and provide an overview of recent promising biofilm control technologies in the food processing sector.

Isolation and characterization of Salmonella spp. from food and food contact surfaces in a chicken processing factory

The presence of Salmonella serotypes is a major safety concern of the food industry and poultry farmers. This study aimed to isolate and identify Salmonella spp. from a chicken processing facility by PCR and pulsed-field gel electrophoresis (PFGE). In addition, the biofilm-forming abilities of the isolated bacteria on stainless steel, silicone rubber, plastic, and chicken skin were also investigated. PCR was used for the confirmation of Salmonella serotypes, and then gene similarity within the same serotype was analyzed by PFGE. As a result, 26 S. Enteritidis isolates were detected at a high rate from both food contact surfaces and chicken products during processing. All of them were 100% genetically identical to the same bacteria. The results indicated that the virulence factors and effective biofilm-forming ability of S. Enteritidis isolates could affect human health and economic revenue. It was also suggested that the visual observation of food and food contact surfaces could be a great concern in the future. The continuous monitoring of S. Enteritidis molecular and biofilm characteristics is needed to increase food safety.

The effect of physico-chemical treatment in reducing Listeria monocytogenes biofilms on lettuce leaf surfaces

The purpose of this research was to characterize Listeria monocytogenes from several environmental and clinical sources and assess the efficacy of single and combined physico-chemical treatments in reducing biofilm on lettuce leaves. PCR analysis of L. monocytogenes isolates collected from different clinical (10 strains) and environmental sources (12 strains) was used to look for the presence of one Listeria-specific gene and five virulence genes. Biofilms of L. monocytogenes were developed on lettuce leaves over 24 h. A 5-min ultrasound and a 300-ppm sodium hypochlorite (NaOCl) wash resulted in similar reductions in cell numbers of 0.82 log CFU cm-2. For chlorine dioxide (ClO2) at 60 ppm, the cell numbers were reduced by ∼5.45 log CFU cm-2. A combined treatment of 5 min of ultrasound plus 300 ppm NaOCl or 40 ppm ClO2, provided maximal efficacy, reducing the number of L. monocytogenes on the lettuce surface to non-detectable levels. Therefore, ClO2 has the potential to replace NaOCl for the disinfection of food products in the food industry.