Prospects for Biocontrol of Vibrio parahaemolyticus Contamination in Blue Mussels (Mytilus edulus)-A Year-Long Study

Characterization and genomic analysis of a broad-spectrum lytic phage PG288: A potential natural therapy candidate for Vibrio infections

Vibrio parahaemolyticus, an important zoonotic pathogen, can cause severe diseases and even death in aquatic animals and humans. As the widespread use of antibiotics gradually diminishes their effectiveness, phages, which can selectively lyse bacteria, are garnering increased attention as a valuable alternative antibacterial strategy. This study characterized PG288, a lytic phage utilizing V. parahaemolyticus strain G855 as its host. Morphologically, the phage features a polyhedral head and a long, non-retractable tail. Bactericidal assays revealed that phage PG288 exhibited a strong lytic ability against V. parahaemolyticus strain G855 and demonstrated a broad host range, as evidenced by the ability to infect several distinct Vibrio species. The one-step growth curve indicated a latent period of approximately 50 min for phage PG288, with a burst size of roughly 92 PFU per cell. Additionally, phage PG288 exhibited remarkable stability within a temperature range of 20-50°C and a pH range of 4-10. Genomic analysis unveiled 105 ORFs within phage PG288, notably devoid of genes associated with antibiotic resistance, virulence, and lysogenic activity. Phylogenetic analysis conclusively identified it as a new member of the genus Mardecavirus within the class Caudoviricetes. In summary, this study contributes valuable insights to the phage database, presenting phage PG288 as a promising candidate for phage therapies against Vibrio infections.

Inoviridae prophage and bacterial host dynamics during diversification, succession, and Atlantic invasion of Pacific-native Vibrio parahaemolyticus

IMPORTANCE

An understanding of the processes that contribute to the emergence of pathogens from environmental reservoirs is critical as changing climate precipitates pathogen evolution and population expansion. Phylogeographic analysis of Vibrio parahaemolyticus hosts combined with the analysis of their Inoviridae phage resolved ambiguities of diversification dynamics which preceded successful Atlantic invasion by the epidemiologically predominant ST36 lineage. It has been established experimentally that filamentous phage can limit host recombination, but here, we show that phage loss is linked to rapid bacterial host diversification during epidemic spread in natural ecosystems alluding to a potential role for ubiquitous inoviruses in the adaptability of pathogens. This work paves the way for functional analyses to define the contribution of inoviruses in the evolutionary dynamics of environmentally transmitted pathogens.

Characterization and Genome Analysis of Vibrio campbellii Lytic Bacteriophage OPA17

Vibrio campbellii is a marine bacterium that is associated with luminous vibriosis, especially in the hatchery and nursery stages of penaeid shrimp cultivation worldwide, which has led to low survival rates of shrimp during aquaculture. Phage therapy has been reported as an alternative biocontrol agent which can reduce or replace the use of antibiotics and other chemicals. This study characterized a lytic V. campbellii bacteriophage, OPA17, originally isolated from bloody clams and investigated its biocontrol efficacy against V. campbellii infection in a model system, Artemia franciscana. Phage OPA17 lysed 83.89% of V. campbellii strains tested (n = 118) with clear plaque morphology. Some strains of Vibrio parahaemolyticus and Vibrio vulnificus were also infected by phage OPA17. Transmission electron microscopy and genetic features indicated that OPA17 belongs to the Siphoviridae family. The latent period and burst size of OPA17 were approximately 50 min and 123 PFU/cell, respectively. Moreover, it survived in artificial seawater throughout the 2-month study period and effectively destroyed Vibrio campbellii biofilms after 4 h of incubation. The addition of OPA17 significantly increased the survival of A. franciscana nauplii infected with V. campbellii. The genome sequence of OPA17 showed that it does not carry genes unsuitable for phage therapy. The phylogenetic tree analysis showed that OPA17 was closely related to the V. vulnificus lytic phage SSP002 (98.90% similarity), which was previously reported as a potential biocontrol agent. Accordingly, the results of this study provide valuable information regarding the potential biocontrol application of phage OPA17 against V. campbellii. IMPORTANCE V. campbellii is an emerging luminous pathogen associated with vibriosis, especially in marine shrimp hatcheries. Several strategies, including pond management and use of natural antimicrobials and probiotics, have been studied for control of this organism. Phage therapy is considered one of the effective biocontrol strategies against bacterial infections in aquaculture. However, there has been limited study of V. campbellii bacteriophages. In this study, V. campbellii-specific bacteriophage OPA17 was isolated, characterized, and investigated for its biocontrol efficacy against V. campbellii infection in an Artemia nauplii model. Phage OPA17 belongs to the Siphoviridae family and shares significant genome similarity to phage SSP002, a potential biocontrol agent against V. vulnificus infection in a murine model. However, the host range of OPA17 was broader than that of SSP002. Overall, we discuss the potential of OPA17 for phage therapy application in shrimp hatcheries.

Natural Killers: Opportunities and Challenges for the Use of Bacteriophages in Microbial Food Safety from the One Health Perspective

Ingestion of food or water contaminated with pathogenic bacteria may cause serious diseases. The One Health approach may help to ensure food safety by anticipating, preventing, detecting, and controlling diseases that spread between animals, humans, and the environment. This concept pays special attention to the increasing spread and dissemination of antibiotic-resistant bacteria, which are considered one of the most important environment-related human and animal health hazards. In this context, the development of innovative, versatile, and effective alternatives to control bacterial infections in order to assure comprehensive food microbial safety is becoming an urgent issue. Bacteriophages (phages), viruses of bacteria, have gained significance in the last years due to the request for new effective antimicrobials for the treatment of bacterial diseases, along with many other applications, including biotechnology and food safety. This manuscript reviews the application of phages in order to prevent food- and water-borne diseases from a One Health perspective. Regarding the necessary decrease in the use of antibiotics, results taken from the literature indicate that phages are also promising tools to help to address this issue. To assist future phage-based real applications, the pending issues and main challenges to be addressed shortly by future studies are also taken into account.

Role of Bacteriophages in the Evolution of Pathogenic Vibrios and Lessons for Phage Therapy

Viruses of bacteria, i.e., bacteriophages (or phages for short), were discovered over a century ago and have played a major role as a model system for the establishment of the fields of microbial genetics and molecular biology. Despite the relative simplicity of phages, microbiologists are continually discovering new aspects of their biology including mechanisms for battling host defenses. In turn, novel mechanisms of host defense against phages are being discovered at a rapid clip. A deeper understanding of the arms race between bacteria and phages will continue to reveal novel molecular mechanisms and will be important for the rational design of phage-based prophylaxis and therapies to prevent and treat bacterial infections, respectively. Here we delve into the molecular interactions of Vibrio species and phages.

Tracking the phage trends: A comprehensive review of applications in therapy and food production

In the present scenario, the challenge of emerging antimicrobial resistance is affecting human health globally. The increasing incidences of multidrug-resistant infections have become harder to treat, causing high morbidity, and mortality, and are posing extensive financial loss. Limited discovery of new antibiotic molecules has further complicated the situation and has forced researchers to think and explore alternatives to antibiotics. This has led to the resurgence of the bacteriophages as an effective alternative as they have a proven history in the Eastern world where lytic bacteriophages have been used since their first implementation over a century ago. To help researchers and clinicians towards strengthening bacteriophages as a more effective, safe, and economical therapeutic alternative, the present review provides an elaborate narrative about the important aspects of bacteriophages. It abridges the prerequisite essential requirements of phage therapy, the role of phage biobank, and the details of immune responses reported while using bacteriophages in the clinical trials/compassionate grounds by examining the up-to-date case reports and their effects on the human gut microbiome. This review also discusses the potential of bacteriophages as a biocontrol agent against food-borne diseases in the food industry and aquaculture, in addition to clinical therapy. It finishes with a discussion of the major challenges, as well as phage therapy and phage-mediated biocontrols future prospects.

Bacteriostatic effects of phage F23s1 and its endolysin on Vibrio parahaemolyticus

Vibrio parahaemolyticus is a common foodborne pathogenic bacterium and drug-resistant strains are now widespread. Phages led by drug-resistant V. parahaemolyticus strains are promising means to decrease the pressure on public health. We isolated a V. parahaemolyticus-specific bacteriophage F23s1 that was active at wide ranges of temperature (30-60°C) and pH (4-10). Phage F23s1 exhibited a specific host range; in that, only 13 of the 23 V. parahaemolyticus strains were lysed. F23s1 effectively inhibited the growth of V. parahaemolyticus strain F23 in shrimp at 25°C within 12 h at a multiplicity of infection of 1000. We sequenced the genome of phage F23s1 which comprised a 76,648-bp DNA with 105 open reading frames (ORFs) and identified an endolysin gene ORF52 that was then cloned and successfully expressed in Escherichia coli. The recombinant ORF52 protein significantly decreased OD_600 nm of V. parahaemolyticus F23 from 0.978 to 0.249 when used at 20 µmol/L within 60 min. The endolysin also showed lytic activity against a panel of 23 drug-resistant V. parahaemolyticus and 12 Salmonella strains with a higher lytic ability for V. parahaemolyticus. The phage F23s1 and its endolysin will be useful for preventing and controlling V. parahaemolyticus in food safety.

In Vivo Bacteriophages’ Application for the Prevention and Therapy of Aquaculture Animals–Chosen Aspects

To meet the nutritional requirements of our growing population, animal production must double by 2050, and due to the exhaustion of environmental capacity, any growth will have to come from aquaculture. Aquaculture is currently undergoing a dynamic development, but the intensification of production increases the risk of bacterial diseases. In recent years, there has been a drastic development in the resistance of pathogenic bacteria to antibiotics and chemotherapeutic agents approved for use, which has also taken place in aquaculture. Consequently, animal mortality and economic losses in livestock have increased. The use of drugs in closed systems is an additional challenge as it can damage biological filters. For this reason, there has been a growing interest in natural methods of combating pathogens. One of the methods is the use of bacteriophages both for prophylactic purposes and therapy. This work summarizes the diverse results of the in vivo application of bacteriophages for the prevention and control of bacterial pathogens in aquatic animals to provide a reference for further research on bacteriophages in aquaculture and to compare major achievements in the field.

Tackling Vibrio parahaemolyticus in ready-to-eat raw fish flesh slices using lytic phage VPT02 isolated from market oyster

The opportunistic pathogen V. parahaemolyticus is a major causative agent for seafood-borne illness worldwide. It also causes severe vibriosis in aquaculture animals, affecting seafood production with huge economic loss. These issues are getting worse due to the current global warming in oceans, spread of antibiotic resistance, and changes in consumer preference toward ready-to-eat (RTE) food items including seafood. To answer the urgent need for sustainable biocontrol agents against V. parahaemolyticus, we isolated and characterized a novel lytic bacteriophage VPT02 from market oyster. VPT02 lysed antibiotic resistant V. parahaemolyticus strains including FORC_023. Moreover, it exhibited notable properties as a biocontrol agent suitable for seafood-related settings, like short eclipse/latent periods, high burst size, broad thermal and pH stability, and no toxin/antibiotic resistance genes in the genome. Further comparative genomic analysis with the previously reported homologue phage pVp-1 revealed that VPT02 additionally possesses genes related to the nucleotide scavenging pathway, presumably enabling the phage to propagate quickly. Consistent with its strong in vitro bacteriolytic activity, treatment of only a small quantity of VPT02 (multiplicity of infection of 10) significantly increased the survival rate of V. parahaemolyticus-infected brine shrimp (from 16.7% to 46.7%). When applied to RTE raw fish flesh slices, the same quantity of VPT02 achieved up to 3.9 log reduction of spiked V. parahaemolyticus compared with the phage untreated control. Taken together, these results suggest that VPT02 may be a sustainable anti-V. parahaemolyticus agent useful in seafood-related settings including for RTE items.

Phage Therapy as a Focused Management Strategy in Aquaculture

Therapeutic bacteriophages, commonly called as phages, are a promising potential alternative to antibiotics in the management of bacterial infections of a wide range of organisms including cultured fish. Their natural immunogenicity often induces the modulation of a variated collection of immune responses within several types of immunocytes while promoting specific mechanisms of bacterial clearance. However, to achieve standardized treatments at the practical level and avoid possible side effects in cultivated fish, several improvements in the understanding of their biology and the associated genomes are required. Interestingly, a particular feature with therapeutic potential among all phages is the production of lytic enzymes. The use of such enzymes against human and livestock pathogens has already provided in vitro and in vivo promissory results. So far, the best-understood phages utilized to fight against either Gram-negative or Gram-positive bacterial species in fish culture are mainly restricted to the Myoviridae and Podoviridae, and the Siphoviridae, respectively. However, the current functional use of phages against bacterial pathogens of cultured fish is still in its infancy. Based on the available data, in this review, we summarize the current knowledge about phage, identify gaps, and provide insights into the possible bacterial control strategies they might represent for managing aquaculture-related bacterial diseases.

Presence, Seasonal Distribution, and Biomolecular Characterization of Vibrio parahaemolyticus and Vibrio vulnificus in Shellfish Harvested and Marketed in Sardinia (Italy) between 2017 and 2018

ABSTRACT

In the present study, we investigated the presence, seasonal distribution, and biomolecular characteristics of Vibrio parahaemolyticus and Vibrio vulnificus in samples of bivalve mollusks (Mytilus galloprovincialis, Crassostrea gigas, and Ruditapes decussatus) harvested and marketed in Sardinia (Italy) between 2017 and 2018. A total of 435 samples were submitted for qualitative determination of Vibrio spp., V. parahaemolyticus, and V. vulnificus. Potentially enteropathogenic isolates were detected with biomolecular methods. The overall prevalence of Vibrio spp. was 7.6%. The highest Vibrio prevalence was found in R. decussatus (8.3%). The prevalences of V. parahaemolyticus and V. vulnificus were 2.7 and 4.8%, respectively. Higher prevalences of V. parahaemolyticus and V. vulnificus were found in R. decussatus (4.2%) and C. gigas (6.2%), respectively. Only two pathogenic V. parahaemolyticus strains were recovered (genotypes: tdh- and trh+; tdh+ and trh-), both from M. galloprovincialis. None of the isolates were tdh+ and trh+. Pathogenic Vibrio infections are often underestimated, and human infections are increasing in Europe. European data on the true distribution of Vibrionaceae are scarce, and the results of the present study highlight the need of constant monitoring to update the distribution of pathogenic vibrios.

HIGHLIGHTS

Phage therapy as a potential approach in the biocontrol of pathogenic bacteria associated with shellfish consumption

Infectious human diseases acquired from bivalve shellfish consumption constitute a public health threat. These health threats are largely related to the filter-feeding phenomenon, by which bivalve organisms retain and concentrate pathogenic bacteria from their surrounding waters. Even after depuration, bivalve shellfish are still involved in outbreaks caused by pathogenic bacteria, which increases the demand for new and efficient strategies to control transmission of shellfish infection. Bacteriophage (or phage) therapy represents a promising, tailor-made approach to control human pathogens in bivalves, but its success depends on a deep understanding of several factors that include the bacterial communities present in the harvesting waters, the appropriate selection of phage particles, the multiplicity of infection that produces the best bacterial inactivation, chemical and physical factors, the emergence of phage-resistant bacterial mutants and the life cycle of bivalves. This review discusses the need to advance phage therapy research for bivalve decontamination, highlighting their efficiency as an antimicrobial strategy and identifying critical aspects to successfully apply this therapy to control human pathogens associated with bivalve consumption.

Virulence, resistance, and genetic diversity of Vibrio parahaemolyticus recovered from commonly consumed aquatic products in Shanghai, China

Vibrio parahaemolyticus can cause severe gastroenteritis, septicaemia and even death in humans. Continuous monitoring of V. parahaemolyticus contamination in aquatic products is imperative for ensuring food safety. In this study, we isolated and characterized 561 V. parahaemolyticus strains recovered from 23 species of commonly consumed shellfish, crustaceans, and fish collected in July and August of 2017 in Shanghai, China. The bacterium was not isolated from two fish species Carassius auratus and Parabramis pekinensis. The results revealed a very low occurrence of pathogenic V. parahaemolyticus carrying the toxin genes trh (0.2%) and tdh (0.0%). However, high percentages of resistance to the antimicrobial agents ampicillin (93.0%), rifampin (82.9%), streptomycin (75.4%) and kanamycin (50.1%) were found. A high incidence of tolerance to the heavy metals Hg²⁺ (74.7%) and Zn²⁺ (56.2%) was also observed in the isolates. ERIC-PCR-based fingerprinting of MDR isolates (77.5%) revealed 428 ERIC-genotypes, demonstrating remarkable genetic variation among the isolates. The results of this study support the urgent need for food safety risk assessment of aquatic products.

Phages as a Cohesive Prophylactic and Therapeutic Approach in Aquaculture Systems

Facing antibiotic resistance has provoked a continuously growing focus on phage therapy. Although the greatest emphasis has always been placed on phage treatment in humans, behind phage application lies a complex approach that can be usefully adopted by the food industry, from hatcheries and croplands to ready-to-eat products. Such diverse businesses require an efficient method for combating highly pathogenic bacteria since antibiotic resistance concerns every aspect of human life. Despite the vast abundance of phages on Earth, the aquatic environment has been considered their most natural habitat. Water favors multidirectional Brownian motion and increases the possibility of contact between phage particles and their bacterial hosts. As the global production of aquatic organisms has rapidly grown over the past decades, phage treatment of bacterial infections seems to be an obvious and promising solution in this market sector. Pathogenic bacteria, such as Aeromonas and Vibrio, have already proved to be responsible for mass mortalities in aquatic systems, resulting in economic losses. The main objective of this work is to summarize, from a scientific and industry perspective, the recent data regarding phage application in the form of targeted probiotics and therapeutic agents in aquaculture niches.

Bacterial metagenome analysis of Mytilus galloprovincialis collected from Istanbul and Izmir coastal stations of Turkey

Mytilus galloprovincialis is a marine mollusk belonging to the Bivalvia class. It has been distributed largely in Turkish shores and worldwide aquatic environments. Besides being known as an environmental pollution indicator, it is highly consumed as a food and has a high economic value. Due to their nutritional mechanisms by filtering water, they are affected by pollution in seawater and mussels can host-microbial diversity of environmental origin as well as pathogenic bacteria. Therefore, in this study, bacterial species found in Mediterranean mussels collected from the coastal stations of Istanbul [Rumeli Kavagi (RK), Kucukcekmece (KC)], and Izmir [(Foca (MF), Urla (MU)] were investigated and compared with microbiological and metagenomic analyses. According to microbiological analysis results, 34 mussel-associated Enterobacteriaceae and Vibrionaceae family members were identified. As a result of the culture-independent metagenomic analysis, taxonomic groups for each station were identified and compared based on Operational Taxonomic Unit data. For all stations, the most abundant bacterial genera were the unclassified bacterial genera. The total number of mussel-related total richness identified in all groups was 4889 (RK = 1605; KC = 1930; MF = 1508; and MU = 1125). According to the metagenomic data obtained in this study, different relative amounts of Lachnospiraceae and Bacteroidetes taxa groups were reported for all stations. The pathogenic bacterial genera identified by metagenomic analyses which may be significant for the public health are Arcobacter, Clostridium, Aeromonas, Vibrio, Escherichia_Shigella, Klebsiella, Campylobacter, Helicobacter, Pseudomonas, Morganella, Serratia, Corynebacterium, Enterococcus, Staphylococcus, Yersinia, Mycoplasma, Brucellaceae_unclassified, Pantoea, and Proteus.