Application of Bacteriophages to Control Vibrio alginolyticus Contamination in Oyster (Saccostrea glomerata) Larvae

Probiotics from kefir: Evaluating their immunostimulant and antioxidant potential in the carpet shell clam (Ruditapesdecussatus)

This study aimed to investigate the impact of incorporating kefir into the diet on biometric parameters, as well as the immune and antioxidant responses of the carpet shell clam (Ruditapes decussatus) after an experimental infection by Vibrio alginolyticus. Clams were divided into a control group and a treated group. The control group was fed on spirulina (Arthrospira platensis) alone. While, the treated group was fed on spirulina supplemented with 10% dried kefir. After 21 days, clams were immersed in a suspension of V. alginolyticus 5 × 105 CFU mL -1 for 30 min. Seven days after experimental infection, survival was 100% in both groups. The obtained results showed a slight increase in weight and condition index in clams fed with kefir-supplemented diet for 21 days compared to control clams. Regarding antioxidant responses, the treated group showed higher superoxide dismutase activity compared to the control group. However, the malondialdehyde level was lower in the treated clams than in the control. In terms of immune parameters, the treated group showed slightly elevated activities of phenoloxidase, lysozyme and alkaline phosphatase, whereas a decreased lectin activity was observed compared to the control group. The obtained results suggest that kefir enhanced both the antioxidant and immune response of infected clams.

Bacteriophages to control Vibrio alginolyticus in live feeds prior to their administration in larviculture

AIMS

This study aimed to evaluate the efficiency of two phages [VB_VaC_TDDLMA (phage TDD) and VB_VaC_SRILMA (phage SRI)] alone and in a cocktail to control Vibrio alginolyticus in brine shrimp before their administration in larviculture.

METHODS AND RESULTS

Phages were isolated from seawater samples and characterized by host spectrum, growth parameters, adsorption rate, genomic analysis, and inactivation efficiency. Both phages belong to the Caudoviricetes class and lack known virulence or antibiotic-resistance genes. They exhibit specificity, infecting only their host, V. alginolyticus CECT 521. Preliminary experiments in a culture medium showed that phage TDD (reduction of 5.8 log CFU ml-1 after 10 h) outperformed phage SRI (reduction of 4.6 log CFU ml-1 after 6 h) and the cocktail TDD/SRI (reduction of 5.2 log CFU ml-1 after 8 h). In artificial marine water experiments with Artemia franciscana, both single phage suspensions and the phage cocktail, effectively inactivated V. alginolyticus in culture water (reduction of 4.3, 2.1, and 1.9 log CFU ml-1 for phages TDD, SRI, and the phage cocktail, respectively, after 12 h) and in A. franciscana (reduction of 51.6%, 87.3%, and 85.3% for phages TDD, SRI, and the phage cocktail, respectively, after 24 h). The two phages and the phage cocktail did not affect A. franciscana natural microbiota or other Vibrio species in the brine shrimp.

CONCLUSIONS

The results suggest that phages can safely and effectively control V. alginolyticus in A. franciscana prior to its administration in larviculture.

Vibrio-infecting bacteriophages and their potential to control biofilm

The emergence and spread of antibiotic-resistant pathogenic bacteria have necessitated finding new control alternatives. Under these circumstances, lytic bacteriophages offer a viable and promising option. This review focuses on Vibrio-infecting bacteriophages and the characteristics that make them suitable for application in the food and aquaculture industries. Bacteria, particularly Vibrio spp., can produce biofilms under stress conditions. Therefore, this review summarizes several anti-biofilm mechanisms that phages have, such as stimulating the host bacteria to produce biofilm-degrading enzymes, utilizing tail depolymerases, and penetrating matured biofilms through water channels. Additionally, the advantages of bacteriophages over antibiotics, such as a lower probability of developing resistance and the ability to infect dormant cells, are discussed. Finally, this review presents future research prospects related to further utilization of phages in diverse fields.

The Safety of Bacteriophages in Treatment of Diseases Caused by Multidrug-Resistant Bacteria

Given the urgency due to the rapid emergence of multidrug-resistant (MDR) bacteria, bacteriophages (phages), which are viruses that specifically target and kill bacteria, are rising as a potential alternative to antibiotics. In recent years, researchers have begun to elucidate the safety aspects of phage therapy with the aim of ensuring safe and effective clinical applications. While phage therapy has generally been demonstrated to be safe and tolerable among animals and humans, the current research on phage safety monitoring lacks sufficient and consistent data. This emphasizes the critical need for a standardized phage safety assessment to ensure a more reliable evaluation of its safety profile. Therefore, this review aims to bridge the knowledge gap concerning phage safety for treating MDR bacterial infections by covering various aspects involving phage applications, including phage preparation, administration, and the implications for human health and the environment.

Perturbation of Quorum Sensing after the Acquisition of Bacteriophage Resistance Could Contribute to Novel Traits in Vibrio alginolyticus

Bacteria employ a wide range of molecular mechanisms to confer resistance to bacteriophages, and these mechanisms are continuously being discovered and characterized. However, there are instances where certain bacterial species, despite lacking these known mechanisms, can still develop bacteriophage resistance through intricate metabolic adaptation strategies, potentially involving mutations in transcriptional regulators or phage receptors. Vibrio species have been particularly useful for studying the orchestrated metabolic responses of Gram-negative marine bacteria in various challenges. In a previous study, we demonstrated that Vibrio alginolyticus downregulates the expression of specific receptors and transporters in its membrane, which may enable the bacterium to evade infection by lytic bacteriophages. In our current study, our objective was to explore how the development of bacteriophage resistance in Vibrio species disrupts the quorum-sensing cascade, subsequently affecting bacterial physiology and metabolic capacity. Using a real-time quantitative PCR (rt-QPCR) platform, we examined the expression pattern of quorum-sensing genes, auto-inducer biosynthesis genes, and cell density regulatory proteins in phage-resistant strains. Our results revealed that bacteriophage-resistant bacteria downregulate the expression of quorum-sensing regulatory proteins, such as LuxM, LuxN, and LuxP. This downregulation attenuates the normal perception of quorum-sensing peptides and subsequently diminishes the expression of cell density regulatory proteins, including LuxU, aphA, and LuxR. These findings align with the diverse phenotypic traits observed in the phage-resistant strains, such as altered biofilm formation, reduced planktonic growth, and reduced virulence. Moreover, the transcriptional depletion of aphA, the master regulator associated with low cell density, was linked to the downregulation of genes related to virulence. This phenomenon appears to be phage-specific, suggesting a finely tuned metabolic adaptation driven by phage-host interaction. These findings contribute to our understanding of the role of Vibrio species in microbial marine ecology and highlight the complex interplay between phage resistance, quorum sensing, and bacterial physiology.

Characterization of vB_ValM_PVA8, a broad-host-range bacteriophage infecting Vibrio alginolyticus and Vibrio parahaemolyticus

Phage therapy was taken as an alternative strategy to antibiotics in shrimp farming for the control of Vibrio species of Vibrio parahaemolyticus and Vibrio alginolyticus, which cause substantial mortality and significant economic losses. In this study, a new Vibrio phage vB_ValM_PVA8 (PVA8), which could efficiently infect pathogenic isolates of V. alginolyticus and V. parahaemolyticus, was isolated from sewage water and characterized by microbiological and in silico genomic analyses. The phage was characterized to be a member of the Straboviridae family with elongated head and contractile tail by transmission electron microscopy. Genome sequencing showed that PVA8 had a 246,348-bp double-stranded DNA genome with a G + C content of 42.6%. It harbored totally 388 putative open reading frames (ORFs), among them 92 (23.71%) assigned to functional genes. Up to 27 transfer RNA (tRNA) genes were found in the genome, and the genes for virulence, antibiotic resistance, and lysogeny were not detected. NCBI genomic blasting results and the phylogenetic analysis based on the sequences of the large terminase subunits and the DNA polymerase indicated that PVA8 shared considerable similarity with Vibrio phage V09 and bacteriophage KVP40. The phage had a latent period of 20 min and a burst size of 309 PFUs/infected cell with the host V. alginolyticus, and it was stable over a broad pH range (4.0-11.0) and a wide temperature span (-80°C to 60°C), respectively, which may benefit its feasibility for phage therapy. In addition, it had the minimum multiplicity of infection (MOI) of 0.0000001, which revealed its strong multiplication capacity. The shrimp cultivation lab trials demonstrated that PVA8 could be applied in treating pathogenic V. parahaemolyticus infection disease of shrimp with a survival rate of 88.89% comparing to that of 34.43% in the infected group, and the pond application trails confirmed that the implementation of PVA8 could rapidly yet effectively reduce the level of the Vibrio. Taken together, PVA8 may be potential to be explored as a promising biological agent for Vibrio control in aquaculture farming industry.

Interactions of Vibrio phages and their hosts in aquatic environments

Bacteriophages (phages) are viruses that specifically infect bacteria. These viruses were discovered a century ago and have been used as a model system in microbial genetics and molecular biology. In order to survive, bacteria have to quickly adapt to phage challenges in their natural settings. In turn, phages continuously develop/evolve mechanisms for battling host defenses. A deeper understanding of the arms race between bacteria and phages is essential for the rational design of phage-based prophylaxis and therapies to prevent and treat bacterial infections. Vibrio species and their phages (vibriophages) are a suitable model to study these interactions. Phages are highly ubiquitous in aquatic environments and Vibrio are waterborne bacteria that must survive the constant attack by phages for successful transmission to their hosts. Here, we review relevant literature from the past two years to delve into the molecular interactions of Vibrio species and their phages in aquatic niches.

Recent advances in phage defense systems and potential overcoming strategies

Bacteriophages are effective in the prevention and control of bacteria, and many phage products have been permitted and applied in the field. Because bacteriophages are expected to replace other antimicrobial agents like antibiotics, the antibacterial effect of bacteriophage has attracted widespread attention. Recently, the diversified defense systems discovered in the target host have become potential threats to the continued effective application of phages. Therefore, a systematic summary and in-depth illustration of the interaction between phages and bacteria is conducive to the development of this biological control approach. In this review, we introduce different defense systems in bacteria against phages and emphasize newly discovered defense mechanisms in recent years. Additionally, we draw attention to the striking resemblance between defense system genes and antibiotic resistance genes, which raises concerns about the potential transfer of phage defense systems within bacterial populations and its future impact on phage efficacy. Thus, attention should be given to the effects of phage defense genes in practical applications. This article is not exhaustive, but strategies to overcome phage defense systems are also discussed to further promote more efficient use of phages.

Genome Characterization and Infectivity Potential of Vibriophage-ϕLV6 with Lytic Activity against Luminescent Vibrios of Penaeus vannamei Shrimp Aquaculture

Shrimp aquaculture, especially during the hatchery phase, is prone to economic losses due to infections caused by luminescent vibrios. In the wake of antimicrobial resistance (AMR) in bacteria and the food safety requirements of farmed shrimp, aqua culturists are seeking alternatives to antibiotics for shrimp health management, and bacteriophages are fast emerging as natural and bacteria-specific antimicrobial agents. This study analyzed the whole genome of vibriophage-ϕLV6 that showed lytic activity against six luminescent vibrios isolated from the larval tanks of P. vannamei shrimp hatcheries. The Vibriophage-ϕLV6 genome was 79,862 bp long with 48% G+C content and 107 ORFs that coded for 31 predicted protein functions, 75 hypothetical proteins, and a tRNA. Pertinently, the vibriophage-ϕLV6 genome harbored neither AMR determinants nor virulence genes, indicating its suitability for phage therapy. There is a paucity of whole genome-based information on vibriophages that lyse luminescent vibrios, and this study adds pertinent data to the database of V. harveyi infecting phage genomes and, to our knowledge, is the first vibriophage genome report from India. Transmission electron microscopy (TEM) of vibriophage-ϕLV6 revealed an icosahedral head (~73 nm) and a long, flexible tail (~191 nm) suggesting siphovirus morphology. The vibriophage-ϕLV6 phage at a multiplicity of infection (MOI) of 80 inhibited the growth of luminescent V. harveyi at 0.25%, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3% salt gradients. In vivo experiments conducted with post-larvae of shrimp showed that vibriophage-ϕLV6 reduced luminescent vibrio counts and post-larval mortalities in the phage-treated tank compared to the bacteria-challenged tank, suggesting the potentiality of vibriophage-ϕLV6 as a promising candidate in treating luminescent vibriosis in shrimp aquaculture. The vibriophage-ϕLV6 survived for 30 days in salt (NaCl) concentrations ranging from 5 ppt to 50 ppt and was stable at 4 °C for 12 months.

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.

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.

Coastal water bacteriophages infect various sets of Vibrio parahaemolyticus sequence types

Introduction

Gastrointestinal illnesses associated with the consumption of shellfish contaminated with Vibrio parahaemolyticus have a negative impact on the shellfish industry due to recalls and loss of consumer confidence in products. This bacterial pathogen is very diverse and specific sequence types (STs), ST631 and ST36, have emerged as prevalent causes of Vibrio foodborne disease outbreaks in the US, though other STs have been implicated in sporadic cases. We investigated whether bacteriophages could be used as a proxy to monitor for the presence of distinct V. parahaemolyticus STs in coastal waters.

Methods

For this purpose, bacteriophages infecting V. parahaemolyticus were isolated from water samples collected on the Northeast Atlantic coast. The isolated phages were tested against a collection of 29 V. parahaemolyticus isolates representing 18 STs, including six clonal complexes (CC). Four distinct phages were identified based on their ability to infect different sets of V. parahaemolyticus isolates.

Results and Discussion

Overall, the 29 bacterial isolates segregated into one of eight patterns of susceptibility, ranging from resistance to all four phages to susceptibility to any number of phages. STs represented by more than one bacterial isolate segregated within the same pattern of susceptibility except for one V. parahaemolyticus ST. Other patterns of susceptibility included exclusively clinical isolates represented by distinct STs. Overall, this study suggests that phages populating coastal waters could be exploited to monitor for the presence of V. parahaemolyticus STs known to cause foodborne outbreaks.

Isolation and characterization of a novel phage vB_ValP_VA-RY-3 infecting Vibrio alginolyticus

Vibrio alginolyticus is a common foodborne pathogen existing both in contaminated seafood and the environment and can cause serious mortality in aquaculture facilities. Bacteriophages can be used as an alternative bio-control agent to eliminate and reduce pathogens. In this study, a novel lytic phage, designated vB_ValP_VA-RY-3 (referred to as S1R3Y), was isolated from sewage collected in Dalian, China. The linear double-stranded DNA genome of phage S1R3Y is 40.271 kb, which has a mol% G + C content of 43.98, containing 51 ORFs with a T7-like genomic organization. It shared the closest relationship with phage vB_CsaP_Ss1, but the homology coverage is just 6%. S1R3Y lacks tRNA and no known virulence or lysogenic genes were found. S1R3Y had a burst size of 147 PFU/cell and is stable under different temperatures (4-56 °C) and pH (5.0-7.0). A comparison of its genomic features and phylogenetic analysis revealed that phage S1R3Y is a novel member of the order Caudovirales, family Podoviridae. Our results suggest that phage S1R3Y may represent a potential therapeutic agent against Vibrio alginolyticus.

Multidrug-resistant enteric bacteria in Nigeria and potential use of bacteriophages as biocontrol

Enteric bacterial pathogens have been implicated in many cases of gastroenteritis in Nigeria, a West African country. This situation is worsened by some reports of the high prevalence of multidrug-resistant enteric bacteria. To better prepare for situations in which even antibiotics of last resort would fail to treat infections caused by these pathogens, attention should be paid to alternative antimicrobial strategies. Here, we summarize existing reports of multidrug-resistant enteric bacterial infections in Nigeria, and importantly present the use of bacteriophages (viruses of bacteria) as an attractive antimicrobial alternative to combat these pathogens. It is hoped that this review will encourage research into the use of lytic bacteriophages against multidrug-resistant enteric bacteria in Nigeria.

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.

Bacteriophage therapy in aquaculture: current status and future challenges

The escalation of antibiotic resistance has revitalized bacteriophage (phage) therapy. Recently, phage therapy has been gradually applied in medicine, agriculture, food, and environmental fields due to its distinctive features of high efficiency, specificity, and environmental friendliness compared to antibiotics. Likewise, phage therapy also holds great promise in controlling pathogenic bacteria in aquaculture. The application of phage therapy instead of antibiotics to eliminate pathogenic bacteria such as Vibrio, Pseudomonas, Aeromonas, and Flavobacterium and to reduce fish mortality in aquaculture has been frequently reported. In this context, the present review summarizes and analyzes the current status of phage therapy in aquaculture, focusing on the key parameters of phage application, such as phage isolation, selection, dosage, and administration modes, and introducing the strategies and methods to boost efficacy and restrain the emergence of resistance. In addition, we discussed the human safety, environmental friendliness, and techno-economic practicability of phage therapy in aquaculture. Finally, this review outlines the current challenges of phage therapy application in aquaculture from the perspectives of phage resistance, phage-mediated resistance gene transfer, and effects on the host immune system.

Phage Revolution Against Multidrug-Resistant Clinical Pathogens in Southeast Asia

Southeast Asia (SEA) can be considered a hotspot of antimicrobial resistance (AMR) worldwide. As recent surveillance efforts in the region reported the emergence of multidrug-resistant (MDR) pathogens, the pursuit of therapeutic alternatives against AMR becomes a matter of utmost importance. Phage therapy, or the use of bacterial viruses called bacteriophages to kill bacterial pathogens, is among the standout therapeutic prospects. This narrative review highlights the current understanding of phages and strategies for a phage revolution in SEA. We define phage revolution as the radical use of phage therapy in infectious disease treatment against MDR infections, considering the scientific and regulatory standpoints of the region. We present a three-phase strategy to encourage a phage revolution in the SEA clinical setting, which involves: (1) enhancing phage discovery and characterization efforts, (2) creating and implementing laboratory protocols and clinical guidelines for the evaluation of phage activity, and (3) adapting regulatory standards for therapeutic phage formulations. We hope that this review will open avenues for scientific and policy-based discussions on phage therapy in SEA and eventually lead the way to its fullest potential in countering the threat of MDR pathogens in the region and worldwide.

Pathogenic Vibrio Species Are Associated with Distinct Environmental Niches and Planktonic Taxa in Southern California (USA) Aquatic Microbiomes

Interactions between vibrio bacteria and the planktonic community impact marine ecology and human health. Many coastal Vibrio spp. can infect humans, representing a growing threat linked to increasing seawater temperatures. Interactions with eukaryotic organisms may provide attachment substrate and critical nutrients that facilitate the persistence, diversification, and spread of pathogenic Vibrio spp. However, vibrio interactions with planktonic organisms in an environmental context are poorly understood. We quantified the pathogenic Vibrio species V. cholerae, V. parahaemolyticus, and V. vulnificus monthly for 1 year at five sites and observed high abundances, particularly during summer months, with species-specific temperature and salinity distributions. Using metabarcoding, we established a detailed profile of both prokaryotic and eukaryotic coastal microbial communities. We found that pathogenic Vibrio species were frequently associated with distinct eukaryotic amplicon sequence variants (ASVs), including diatoms and copepods. Shared environmental conditions, such as high temperatures and low salinities, were associated with both high concentrations of pathogenic vibrios and potential environmental reservoirs, which may influence vibrio infection risks linked to climate change and should be incorporated into predictive ecological models and experimental laboratory systems. IMPORTANCE Many species of coastal vibrio bacteria can infect humans, representing a growing health threat linked to increasing seawater temperatures. However, their interactions with surrounding microbes in the environment, especially eukaryotic organisms that may provide nutrients and attachment substrate, are poorly understood. We quantified three pathogenic Vibrio species monthly for a duration of 1 year, finding that all three species were abundant and exhibited species-specific temperature and salinity distributions. Using metabarcoding, we investigated associations between these pathogenic species and prokaryotic and eukaryotic microbes, revealing genus and amplicon sequence variant (ASV)-specific relationships with potential functional implications. For example, pathogenic species were frequently associated with chitin-producing eukaryotes, such as diatoms in the genus Thalassiosira and copepods. These associations between high concentrations of pathogenic vibrios and potential environmental reservoirs should be considered when predicting infection risk and developing ecologically relevant model systems.

Phages in Food Industry Biocontrol and Bioremediation

Bacteriophages are ubiquitous in nature and their use is a current promising alternative in biological control. Multidrug resistant (MDR) bacterial strains are present in the livestock industry and phages are attractive candidates to eliminate them and their biofilms. This alternative therapy also reduces the non-desirable effects produced by chemicals on food. The World Health Organization (WHO) estimates that around 420,000 people die due to a foodborne illness annually, suggesting that an improvement in food biocontrol is desirable. This review summarizes relevant studies of phage use in biocontrol focusing on treatments in live animals, plants, surfaces, foods, wastewaters and bioremediation.

Phages in Food Industry Biocontrol and Bioremediation

Bacteriophages are ubiquitous in nature and their use is a current promising alternative in biological control. Multidrug resistant (MDR) bacterial strains are present in the livestock industry and phages are attractive candidates to eliminate them and their biofilms. This alternative therapy also reduces the non-desirable effects produced by chemicals on food. The World Health Organization (WHO) estimates that around 420,000 people die due to a foodborne illness annually, suggesting that an improvement in food biocontrol is desirable. This review summarizes relevant studies of phage use in biocontrol focusing on treatments in live animals, plants, surfaces, foods, wastewaters and bioremediation.

Isolation and Characterization of Six Vibrio parahaemolyticus Lytic Bacteriophages From Seafood Samples

Vibrio parahaemolyticus is a foodborne pathogen that is frequently isolated from a variety of seafood. To control this pathogenic Vibrio spp., the implementation of bacteriophages in aquaculture and food industries have shown a promising alternative to antibiotics. In this study, six bacteriophages isolated from the seafood samples demonstrated a narrow host range specificity that infecting only the V. parahaemolyticus strains. Morphological analysis revealed that bacteriophages Vp33, Vp22, Vp21, and Vp02 belong to the Podoviridae family, while bacteriophages Vp08 and Vp11 were categorized into the Siphoviridae family. All bacteriophages were composed of DNA genome and showed distinctive restriction fragment length polymorphism. The optimal MOI for bacteriophage propagation was determined to be 0.001 to 1. One-step growth curve revealed that the latent period ranged from 10 to 20 min, and the burst size of bacteriophage was approximately 17 to 51 PFU/cell. The influence of temperature and pH levels on the stability of bacteriophages showed that all bacteriophages were optimally stable over a wide range of temperatures and pH levels. In vitro lytic activity of all bacteriophages demonstrated to have a significant effect against V. parahaemolyticus. Besides, the application of a bacteriophage cocktail instead of a single bacteriophage suspension was observed to have a better efficiency to control the growth of V. parahaemolyticus. Results from this study provided a basic understanding of the physiological and biological properties of the isolated bacteriophages before it can be readily used as a biocontrol agent against the growth of V. parahaemolyticus.