Characterization of potential lytic bacteriophage against Vibrio alginolyticus and its therapeutic implications on biofilm dispersal

Biofilm formation in food industries: Challenges and control strategies for food safety

Various pathogens have the ability to grow on food matrices and instruments. This grow may reach to form biofilms. Bacterial biofilms are community of microorganisms embedded in extracellular polymeric substances (EPSs) containing lipids, DNA, proteins, and polysaccharides. These EPSs provide a tolerance and favorable living condition for microorganisms. Biofilm formations could not only contribute a risk for food safety but also have negative impacts on healthcare sector. Once biofilms form, they reveal resistances to traditional detergents and disinfectants, leading to cross-contamination. Inhibition of biofilms formation and abolition of mature biofilms is the main target for controlling of biofilm hazards in the food industry. Some novel eco-friendly technologies such as ultrasound, ultraviolet, cold plasma, magnetic nanoparticles, different chemicals additives as vitamins, D-amino acids, enzymes, antimicrobial peptides, and many other inhibitors provide a significant value on biofilm inhibition. These anti-biofilm agents represent promising tools for food industries and researchers to interfere with different phases of biofilms including adherence, quorum sensing molecules, and cell-to-cell communication. This perspective review highlights the biofilm formation mechanisms, issues associated with biofilms, environmental factors influencing bacterial biofilm development, and recent strategies employed to control biofilm-forming bacteria in the food industry. Further studies are still needed to explore the effects of biofilm regulation in food industries and exploit more regulation strategies for improving the quality and decreasing economic losses.

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.

Characterization and genomic analysis of a lytic Stenotrophomonas maltophilia short-tailed phage A1432 revealed a new genus of the family Mesyanzhinovviridae

Stenotrophomonas maltophilia (S. maltophilia) is an emerging opportunistic pathogen that exhibits resistant to a majority of commonly used antibiotics. Phages have the potential to serve as an alternative treatment for S. maltophilia infections. In this study, a lytic phage, A1432, infecting S. maltophilia YCR3A-1, was isolated and characterized from a karst cave. Transmission electron microscopy revealed that phage A1432 possesses an icosahedral head and a shorter tail. Phage A1432 demonstrated a narrow host range, with an optimal multiplicity of infection of 0.1. The one-step growth curve indicated a latent time of 10 min, a lysis period of 90 min, a burst size of 43.2 plaque-forming units per cell. In vitro bacteriolytic activity test showed that phage A1432 was capable to inhibit the growth of S. maltophilia YCR3A-1 in an MOI-dependent manner after 2 h of co-culture. BLASTn analysis showed that phage A1432 genome shares the highest similarity (81.46%) with Xanthomonas phage Xoo-sp2 in the NCBI database, while the query coverage was only 37%. The phage contains double-stranded DNA with a genome length of 61,660 bp and a GC content of 61.92%. It is predicted to have 79 open reading frames and one tRNA, with no virulence or antibiotic resistance genes. Phylogenetic analysis using terminase large subunit and DNA polymerase indicated that phage A1432 clustered with members of the Bradleyvirinae subfamily but diverged into a distinct branch. Further phylogenetic comparison analysis using Average Nucleotide Identity, proteomic phylogenetic analysis, genomic network analysis confirmed that phage A1432 belongs to a novel genus within the Bradleyvirinae subfamily, Mesyanzhinovviridae family. Additionally, phylogenetic analysis of the so far isolated S. maltophilia phages revealed significant genetic diversity among these phages. The results of this research will contribute valuable information for further studies on their morphological and genetic diversity, will aid in elucidating the evolutionary mechanisms that give rise to them.

Insights into the novel Enterococcus faecalis phage: A comprehensive genome analysis

Enterococcus faecalis, a Gram-positive bacterium, poses a significant clinical challenge owing to its intrinsic resistance to a broad spectrum of antibiotics, warranting urgent exploration of innovative therapeutic strategies. This study investigated the viability of phage therapy as an alternative intervention for antibiotic-resistant E. faecalis, with a specific emphasis on the comprehensive genomic analysis of bacteriophage SAM-E.f 12. The investigation involved whole-genome sequencing of SAM-E.f 12 using Illumina technology, resulting in a robust dataset for detailed genomic characterization. Bioinformatics analyses were employed to predict genes and assign functional annotations. The bacteriophage SAM-E.f 12, which belongs to the Siphoviridae family, exhibited substantial potential, with a burst size of 5.7 PFU/infected cells and a latent period of 20 min. Host range determination experiments demonstrated its effectiveness against clinical E. faecalis strains, positioning SAM-E.f 12 as a precise therapeutic agent. Stability assays underscore resilience across diverse environmental conditions. This study provides a comprehensive understanding of SAM-E.f 12 genomic composition, lytic lifecycle parameters, and practical applications, particularly its efficacy in murine wound models. These results emphasize the promising role of phage therapy, specifically its targeted approach against antibiotic-resistant E. faecalis strains. The nuanced insights derived from this research will contribute to the ongoing pursuit of efficacious phage therapies and offer valuable implications for addressing the clinical challenges associated with E. faecalis infections.

Characterization of Salmonella phages isolated from poultry coops and its effect with nisin on food bio-control

Salmonella is a bacterium associated with food contaminated by various animals, primarily poultry. Interest and research on bacteriophages are increasing because they can be used as an alternative against increasing antibiotic resistance. In our study, eight Salmonella-specific lytic bacteriophages were isolated from chicken feces. Two of the isolated phages (AUFM_Sc1 and AUFM_Sc3) were chosen for their characterization due to their broader host range. Based on morphological and genomic analysis, AUFM_Sc1 was identified to be close to similar Enterobacteria spp. CC31 (Myoviridae) and AUFM_Sc3 was identified to be close to Salmonella phage vB_Sen_I1 (Demerecviridae (formerly Siphoviridae)). Although these phages have shown promise for use in phage therapy applications for chickens, further studies are needed on their suitability. When a cocktail of these phages (AUFM_Sc1 + AUFM_Sc3) and nisin combination was applied on chicken breast meat, it was determined that it was effective against Salmonella contamination and while a good inhibitory effect was observed on the food, especially during the first 48 h, the effect decreased later, but the bacterial concentration was still low compared to the control group. Therefore, it is considered that the combination of AUFM_Sc1 + AUFM_Sc3 + nisin can be used as a food preservative against Salmonella.

Characterization of two bacteriophages specific to Acinetobacter baumannii and their effects on catheters biofilm

Multidrug-resistant strains of Acinetobacter baumannii cause major nosocomial infections. Bacteriophages that are specific to the bacterial species and destroy bacteria can be effectively used for treatment. In this study, we characterized lytic bacteriophages specific to A. baumannii strains. We isolated lytic bacteriophages from environmental water samples and then investigated their morphology, host range, growth characteristics, stability, genome analysis, and biofilm destruction on the catheter surface. Our results showed that the efficacy of the phages varied between 32% and 78%, tested on 78 isolates of A. baumannii; 80 phages were isolated, and two lytic bacteriophages, vB_AbaP_HB01 (henceforth called C2 phage) and vB_AbaM_HB02 (henceforth called K3 phage), were selected for characterization. Electron microscopy scans revealed that the C2 and K3 phages were members of the Podoviridae and Myoviridae families, respectively. Whole-genome sequencing revealed that the sequence of the C2 phage is available in the NCBI database (accession number: OP917929.1), and it was found sequence identity with Acinetobacter phage AB1 18%, the K3 phage DNA sequence is closely related to Acinetobacter phage vB_AbaM_phiAbaA1 (94% similarity). The cocktail of C2 and K3 phages demonstrated a promising decrease in the bacterial cell counts of the biofilm after 4 h. Under a scanning electron microscope, the cocktail treatment destructed the biofilm on the catheter. We propose that the phage cocktail could be a strong alternative to antibiotics to control the A. baumannii biofilm in catheter infections.

Isolation and Characterization of Bacteriophage VA5 against Vibrio alginolyticus

Bacteriophages, or phages, can be used as natural biological control agents to eliminate pathogenic bacteria during aquatic product cultivation. Samples were collected from seafood aquaculture water and aquaculture environmental sewage, and phage VA5 was isolated using the double-layer agar plate method, with Vibrio alginolyticus as the host bacteria. The purified phage strain was subjected to genome sequencing analysis and morphological observation. The optimal multiplicity of infection (MOI), the one-step growth curve, temperature stability, and pH stability were analyzed. Phage VA5 was observed to have a long tail. Whole-genome sequencing revealed that the genome was circular dsDNA, with 35,866 bp length and 46% G+C content. The optimal MOI was 1, the incubation period was 20 min, the outbreak period was 30 min, and the cleavage amount was 92.26 PFU/cell. The phage showed good activity at -20 °C, 70 °C, and pH 2-10. Moreover, the phage VA5 exhibited significant inhibitory effects on V. alginolyticus-infected shrimp culture. The isolated phage VA5 has a wide range of host bacteria and is a good candidate for biological control of pathogenic bacteria.

Isolation, characterization, and genomic analysis of a novel bacteriophage MA9V-1 infecting Chryseobacterium indologenes: a pathogen of Panax notoginseng root rot

Chryseobacterium indologenes is one of the primary causative agents of root rot of Panax notoginseng, which significantly affected plant growth and caused economic losses. With the increasing incidence of antibiotic-resistant bacterial phytopathogens, phage therapy has been garnered renewed attention in treating pathogenic bacteria. However, the therapeutic potential of phage therapy on root rot of P. notoginseng has not been evaluated. In this study, we isolated a novel lytic phage MA9V-1 infecting C. indologenes MA9 from sewage and monitored the formation of clear and round plaques with a diameter of approximately 0.5-1.5 mm. Phage MA9V-1 exhibited rapid absorption (>75% in 8 min), a latency period of 20 min, and a burst size of 10 particles per cell. Transmission electron microscopy indicated that the phage MA9V-1 is a new myovirus hosting C. indologenes MA9. Sequencing of phage genomes revealed that phage MA9V-1 contained a linear double-stranded DNA genome of 213,507 bp with 263 predicted open reading frames, including phage structure, host lysing, and DNA polymerase/helicase but no genes of tRNA, virulence, and antibiotic resistance. Our proteomic tree and genomic analysis revealed that phage MA9V-1 shares identity with Sphingomonas phage PAU and Tenacibaculum phage PTm1; however, they also showed apparent differences. Further systemic evaluation using phage therapy experiments on P. notoginseng suggested that phage MA9V-1 can be a potential candidate for effectively controlling C. indologenes MA9 infection. Thus, we have presented a novel approach to solving root rot in P. notoginseng.

A lytic phage to control multidrug-resistant avian pathogenic Escherichia coli (APEC) infection

The inappropriate use of antibiotics has led to the emergence of multidrug-resistant strains. Bacteriophages (phages) have gained renewed attention as promising alternatives or supplements to antibiotics. In this study, a lytic avian pathogenic Escherichia coli (APEC) phage designated as PEC9 was isolated and purified from chicken farm feces samples. The morphology, genomic information, optimal multiplicity of infection (MOI), one-step growth curve, thermal stability, pH stability, in vitro antibacterial ability and biofilm formation inhibition ability of the phage were determined. Subsequently, the therapeutic effects of the phages were investigated in the mice model. The results showed that PEC9 was a member of the siphovirus-like by electron microscopy observation. Biological characterization revealed that it could lyse two serotypes of E. coli, including O1 (9/20) and O2 (6/20). The optimal multiplicity of infection (MOI) of phage PEC9 was 0.1. Phage PEC9 had a latent period of 20 min and a burst period of 40 min, with an average burst size of 68 plaque-forming units (PFUs)/cell. It maintained good lytic activity at pH 3-11 and 4-50°C and could efficiently inhibit the bacterial planktonic cell growth and biofilm formation, and reduce bacterial counts within the biofilm, when the MOI was 0.01, 0.1, and 1, respectively. Whole-genome sequencing showed that PEC9 was a dsDNA virus with a genome of 44379 bp and GC content of 54.39%. The genome contains 56 putative ORFs and no toxin, virulence, or resistance-related genes were detected. Phylogenetic tree analysis showed that PEC9 is closely related to E. coli phages vB_EcoS_Zar3M, vB_EcoS_PTXU06, SECphi18, ZCEC10, and ZCEC11, but most of these phages exhibit different gene arrangement. The phage PEC9 could successfully protect mice against APEC infection, including improved survival rate, reduced bacterial loads, and organ lesions. To conclude, our results suggest that phage PEC9 may be a promising candidate that can be used as an alternative to antibiotics in the control of APEC infection.

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.

Isolation and characterization of a novel phage belonging to a new genus against Vibrio parahaemolyticus

BACKGROUND

Vibrio parahaemolyticus is a major foodborne pathogen that contaminates aquatic products and causes great economic losses to aquaculture. Because of the emergence of multidrug-resistant V. parahaemolyticus strains, bacteriophages are considered promising agents for their biocontrol as an alternative or supplement to antibiotics. In this study, a lytic vibriophage, vB_VpaM_R16F (R16F), infecting V. parahaemolyticus 1.1997^T was isolated, characterized and evaluated for its biocontrol potential.

METHODS

A vibriophage R16F was isolated from sewage from a seafood market with the double-layer agar method. R16F was studied by transmission electron microscopy, host range, sensitivity of phage particles to chloroform, one-step growth curve and lytic activity. The phage genome was sequenced and in-depth characterized, including phylogenetic and taxonomic analysis.

RESULTS

R16F belongs to the myovirus morphotype and infects V. parahaemolyticus, but not nine other Vibrio spp. As characterized by determining its host range, one-step growth curve, and lytic activity, phage R16F was found to highly effective in lysing host cells with a short latent period (< 10 min) and a small burst size (13 plaque-forming units). R16F has a linear double-stranded DNA with genome size 139,011 bp and a G + C content of 35.21%. Phylogenetic and intergenomic nucleotide sequence similarity analysis revealed that R16F is distinct from currently known vibriophages and belongs to a novel genus. Several genes (e.g., encoding ultraviolet damage endonuclease and endolysin) that may enhance environmental competitiveness were found in the genome of R16F, while no antibiotic resistance- or virulence factor-related gene was detected.

CONCLUSIONS

In consideration of its biological and genetic properties, this newly discovered phage R16F belongs to a novel genus and may be a potential alternate biocontrol agent.

Advance on Engineering of Bacteriophages by Synthetic Biology

Since bacteriophages (phages) were firstly reported at the beginning of the 20th century, the study on them experiences booming-fading-emerging with discovery and overuse of antibiotics. Although they are the hotspots for therapy of antibiotic-resistant strains nowadays, natural phage applications encounter some challenges such as limited host range and bacterial resistance to phages. Synthetic biology, one of the most dramatic directions in the recent 20-years study of microbiology, has generated numerous methods and tools and has contributed a lot to understanding phage evolution, engineering modification, and controlling phage-bacteria interactions. In order to better modify and apply phages by using synthetic biology techniques in the future, in this review, we comprehensively introduce various strategies on engineering or modification of phage genome and rebooting of recombinant phages, summarize the recent researches and potential directions of phage synthetic biology, and outline the current application of engineered phages in practice.

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

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

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.

Strategies for Prevention and Control of Vibriosis in Asian Fish Culture

It is estimated that vibriosis account for about half of the economic losses in Asian fish culture. Consequently, the prevention and control of vibriosis is one of the priority research topics in the field of Asian fish culture disease. Relevant measures have been proposed to control some Vibrios that pose a threat to Asian fish culture, but there are currently only a few effective vaccines available to combat these Vibrios. The purpose of our review is to sum up the main prevention methods and the latest control strategies of seven Vibrio species that cause great harm to Asian aquaculture, including Vibrio harveyi, Vibrio vulnificus, Vibrio parahaemolyticus, Vibrio mimicus, Vibrio anguillarum, Vibrio alginolyticus and Vibrio cholerae. Strategies such as antibiotics, probiotics, bacteriophages, antimicrobials from plants and other natural sources, as well as vaccines, are compared and discussed here. We expect this review will provide some new views and recommendations for the future better prevention and control of vibriosis in Asian fish culture.

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.

The comparison of lytic activity of isolated phage and commercial Intesti bacteriophage on ESBL producer E. coli and determination of Ec_P6 phage efficacy with in vivo Galleria mellonella larvae model

Antibiotic resistance is one of the crucial public health challenges. As a result of rising resistance, as an alternative to antimicrobials, demands for bacteriophage therapy have increased significantly over the years. The objective of this study was to isolate and characterize potentially therapeutic phages active against Escherichia coli (E. coli) and compare the efficacy with commercial Intesti bacteriophage on the extended-spectrum beta-lactamase (ESBL) positive E. coli (ESBL-EC) and performed the effectiveness of bacteriophage using the Galleria mellonella (G. mellonella) larvae model. Intesti bacteriophage is a polyvalent bacteriophage-based drug. The isolated bacteriophages were obtained from the river and clinical isolates of E. coli were used for the enrichment of bacteriophage isolation. The phages were first screened based on plaque morphology and host ranges determined on clinical strains. The susceptibility of phages was determined against 50 clinical isolates of E. coli and eight different laboratory isolates using the spot test technique. E. coli lytic phage Ec_P6 was used to determine the therapeutic and preventive effects on the G. mellonella larvae model. The slides were prepared by G. mellonella hemolymph for cytologic examination, stained with May Grünwald Giemsa (MGG), and evaluated by light microscopy. The results of the activities revealed lytic spectra ranging from 24% to 97%. Overall strains were susceptible to one or more phages from the panel. It was proved that Intesti bacteriophage is very effective in a wide variety of strains of E. coli including test strains, also showed that isolated Ec_P6 phage is as effective as commercial phage. The best MOI of this phage was 0.01, and infectivity decreased above 60 °C. The results suggest that phage is stable at pH values ranging between 5.0 and 9.0. In vivo study was found that in E. coli infection to achieve a survival high rate the infected larvae should be after 2 hours treated with 0.01 MOI phage (10 μL, 10⁶ PFU/mL) and colistin doses (10 μL, 2.5 mg/kg). It also prevented infection, increasing the survival of the larvae compared to the untreated control group. Ec_P6 phage was found to have a potential for the treatment of E. coli infections.

Characterization of the Novel Phage vB_VpaP_FE11 and Its Potential Role in Controlling Vibrio parahaemolyticus Biofilms

Vibrio parahaemolyticus causes aquatic vibriosis. Its biofilm protects it from antibiotics; therefore, a new different method is needed to control V. parahaemolyticus for food safety. Phage therapy represents an alternative strategy to control biofilms. In this study, the lytic Vibrio phage vB_VpaP_FE11 (FE11) was isolated from the sewers of Guangzhou Huangsha Aquatic Market. Electron microscopy analysis revealed that FE11 has a typical podovirus morphology. Its optimal stability temperature and pH range were found to be 20–50 °C and 5–10 °C, respectively. It was completely inactivated following ultraviolet irradiation for 20 min. Its latent period is 10 min and burst size is 37 plaque forming units/cell. Its double-stranded DNA genome is 43,397 bp long, with a G + C content of 49.24% and 50 predicted protein-coding genes. As a lytic phage, FE11 not only prevented the formation of biofilms but also could destroy the formed biofilms effectively. Overall, phage vB_VpaP_FE11 is a potential biological control agent against V. parahaemolyticus and the biofilm it produces.

Bacteriophages: A weapon against mixed-species biofilms in the food processing environment

Mixed-species biofilms represent the most frequent actual lifestyles of microorganisms in food processing environments, and they are usually more resistant to control methods than single-species biofilms. The persistence of biofilms formed by foodborne pathogens is believed to cause serious human diseases. These challenges have encouraged researchers to search for novel, natural methods that are more effective towards mixed-species biofilms. Recently, the use of bacteriophages to control mixed-species biofilms have grown significantly in the food industry as an alternative to conventional methods. This review highlights a comprehensive introduction of mixed-species biofilms formed by foodborne pathogens and their enhanced resistance to anti-biofilm removal strategies. Additionally, several methods for controlling mixed-species biofilms briefly focused on applying bacteriophages in the food industry have also been discussed. This article concludes by suggesting that using bacteriophage, combined with other 'green' methods, could effectively control mixed-species biofilms in the food industry.

First Succinylome Profiling of Vibrio alginolyticus Reveals Key Role of Lysine Succinylation in Cellular Metabolism and Virulence

Recent studies have shown that a key strategy of many pathogens is to use post-translational modification (PTMs) to modulate host factors critical for infection. Lysine succinylation (Ksuc) is a major PTM widespread in prokaryotic and eukaryotic cells, and is associated with the regulation of numerous important cellular processes. Vibrio alginolyticus is a common pathogen that causes serious disease problems in aquaculture. Here we used the affinity enrichment method with LC-MS/MS to report the first identification of 2082 lysine succinylation sites on 671 proteins in V. alginolyticus, and compared this with the lysine acetylation of V. alginolyticus in our previous work. The Ksuc modification of SodB and PEPCK proteins were further validated by Co-immunoprecipitation combined with Western blotting. Bioinformatics analysis showed that the identified lysine succinylated proteins are involved in various biological processes and central metabolism pathways. Moreover, a total of 1,005 (25.4%) succinyl sites on 502 (37.3%) proteins were also found to be acetylated, which indicated that an extensive crosstalk between acetylation and succinylation in V. alginolyticus occurs, especially in three central metabolic pathways: glycolysis/gluconeogenesis, TCA cycle, and pyruvate metabolism. Furthermore, we found at least 50 (7.45%) succinylated virulence factors, including LuxS, Tdh, SodB, PEPCK, ClpP, and the Sec system to play an important role in bacterial virulence. Taken together, this systematic analysis provides a basis for further study on the pathophysiological role of lysine succinylation in V. alginolyticus and provides targets for the development of attenuated vaccines.

Characterization of vB_VpaP_MGD2, a newly isolated bacteriophage with biocontrol potential against multidrug-resistant Vibrio parahaemolyticus

Vibrio parahaemolyticus is a major foodborne pathogen and is also pathogenic to shrimp. Due to the emergence of multidrug-resistant V. parahaemolyticus strains, bacteriophages have shown promise as antimicrobial agents that could be used for controlling antibiotic-resistant strains. Here, a V. parahaemolyticus phage, vB_VpaP_MGD2, was isolated from a clam (Meretrix meretrix) and further characterized to evaluate its potential capability for biocontrol. Podophage vB_VpaP_MGD2 had a wide host range and was able to lyse 27 antibiotic-resistant V. parahaemolyticus strains. A one-step growth curve showed that vB_VpaP_MGD2 has a short latent period of 10 min and a large burst size of 244 phages per cell. Phage vB_VpaP_MGD2 was able to tolerate a wide range of temperature (30 °C-50 °C) and pH (pH 3-pH 10). Two multidrug-resistant strains (SH06 and SA411) were suppressed by treatment with phage vB_VpaP_MGD2 at a multiplicity of infection of 100 for 24 h without apparent regrowth of bacterial populations. The frequency of mutations causing bacteriophage resistance was relatively low (3.1 × 10^-6). Phage vB_VpaP_MGD2 has a double-stranded DNA with a genome size of 45,105 bp. Among the 48 open reading frames annotated in the genome, no lysogenic genes or virulence genes were detected. Sequence comparisons suggested that vB_VpaP_MGD2 is a member of a new species in the genus Zindervirus within the subfamily Autographivirinae. This is the first report of a member of the genus Zindervirus that can infect V. parahaemolyticus. These findings suggest that vB_VpaP_MGD2 may be a candidate biocontrol agent against early mortality syndrome/acute hepatopancreatic necrosis disease (EMS/AHPND) caused by multidrug-resistant V. parahaemolyticus in shrimp production.

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

Mortalities of bivalve larvae and spat linked with Vibrio spp. infection have been described in hatcheries since 1959, causing potential development of resistant bacteria. A reliable and sustainable solution to this problem is yet to be developed. Potential treatment of bacterial infection with bacteriophages is gaining interest in aquaculture as a more sustainable option for managing Vibrio spp. infection. This study assessed the effectiveness of bacteriophages (Φ-5, Φ-6, and Φ-7) against pathogenic Vibrio isolates (USC-26004 and USC-26005). These phage isolates were found to belong to the Myoviridae viral family. A total of 212 ORFs of Φ-5 were identified and annotated. The genome of this phage contained putative thymidine kinase and lysin enzyme. During infections with phages, the OD values of the isolates USC-26005 and USC-26004 remained stable at a much lower reading compared to the control after 9 h of incubation. Mortality rate of oyster (Saccostrea glomerata) larvae was 28.2 ± 3.5% in the bacteriophage treatment group, compared to 77.9 ± 9.1% in the bacterial treatment group after 24 h incubation. Findings of this study indicate that lytic phages might be utilized as potential bio-control agents of luminescent bacterial disease in oyster hatcheries.

Characterization and Genomic Analysis of ValSw3-3, a New Siphoviridae Bacteriophage Infecting Vibrio alginolyticus

A novel lytic bacteriophage, ValSw3-3, which efficiently infects pathogenic strains of Vibrio alginolyticus, was isolated from sewage water and characterized by microbiological and in silico genomic analyses. Transmission electron microscopy indicated that ValSw3-3 has the morphology of siphoviruses. This phage can infect four species in the Vibrio genus and has a latent period of 15 min and a burst size of 95 ± 2 PFU/infected bacterium. Genome sequencing results show that ValSw3-3 has a 39,846-bp double-stranded DNA genome with a GC content of 43.1%. The similarity between the genome sequences of ValSw3-3 and those of other phages recorded in the GenBank database was below 50% (42%), suggesting that ValSw3-3 significantly differs from previously reported phages at the DNA level. Multiple genome comparisons and phylogenetic analysis based on the major capsid protein revealed that phage ValSw3-3 is grouped in a clade with five other phages, including Listonella phage phiHSIC (GenBank accession no. NC_006953.1), Vibrio phage P23 (MK097141.1), Vibrio phage pYD8-B (NC_021561.1), Vibrio phage 2E1 (KX507045.1), and Vibrio phage 12G5 (HQ632860.1), and is distinct from all known genera within the Siphoviridae family that have been ratified by the International Committee on Taxonomy of Viruses (ICTV). An in silico proteomic comparison of diverse phages from the Siphoviridae family supported this clustering result and suggested that ValSw3-3, phiHSIC, P23, pYD8-B, 2E1, and 12G5 should be classified as a novel genus cluster of Siphoviridae A subsequent analysis of core genes also revealed the common genes shared within this new cluster. Overall, these results provide a characterization of Vibrio phage ValSw3-3 and support our proposal of a new viral genus within the family Siphoviridae IMPORTANCE Phage therapy has been considered a potential alternative to antibiotic therapy in treating bacterial infections. For controlling the vibriosis-causing pathogen Vibrio alginolyticus, well-documented phage candidates are still lacking. Here, we characterize a novel lytic Vibrio phage, ValSw3-3, based on its morphology, host range and infectivity, growth characteristics, stability under various conditions, and genomic features. Our results show that ValSw3-3 could be a potent candidate for phage therapy to treat V. alginolyticus infections due to its stronger infectivity and better pH and thermal stability than those of previously reported Vibrio phages. Moreover, genome sequence alignments, phylogenetic analysis, in silico proteomic comparison, and core gene analysis all support that this novel phage, ValSw3-3, and five unclassified phages form a clade distant from those of other known genera ratified by the ICTV. Thus, we propose a new viral genus within the Siphoviridae family to accommodate this clade, with ValSw3-3 as a representative member.

Escherichia coli and Salmonella Enteritidis dual-species biofilms: interspecies interactions and antibiofilm efficacy of phages

Escherichia coli and Salmonella Enteritidis are foodborne pathogens forming challenging biofilms that contribute to their virulence, antimicrobial resistance, and survival on surfaces. Interspecies interactions occur between species in mixed biofilms promoting different outcomes to each species. Here we describe the interactions between E. coli and S. Enteritidis strains, and their control using specific phages. Single-species biofilms presented more cells compared to dual-species biofilms. The spatial organization of strains, observed by confocal microscopy, revealed similar arrangements in both single- and dual-species biofilms. The EPS matrix composition, assessed by Fourier-transform infrared spectroscopy, disclosed that the spectra extracted from the different dual-species biofilms can either be a combination of both species EPS matrix components or that the EPS matrix of one species predominates. Phages damaged more the single-species biofilms than the mixed biofilms, showing also that the killing efficacy was greatly dependent on the phage growth characteristics, bacterial growth parameters, and bacterial spatial distribution in biofilms. This combination of methodologies provides new knowledge of species-species and phage-host interactions in biofilms of these two major foodborne pathogens.

Advanced strategies for combating bacterial biofilms

Biofilms are communities of microorganisms that are formed on and attached to living or nonliving surfaces and are surrounded by an extracellular polymeric material. Biofilm formation enjoys several advantages over the pathogens in the colonization process of medical devices and patients' organs. Unlike planktonic cells, biofilms have high intrinsic resistance to antibiotics and sanitizers, and overcoming them is a significant problematic challenge in the medical and food industries. There are no approved treatments to specifically target biofilms. Thus, it is required to study and present innovative and effective methods to combat a bacterial biofilm. In this review, several strategies have been discussed for combating bacterial biofilms to improve healthcare, food safety, and industrial process.

Isolation and characterisation of pVa-21, a giant bacteriophage with anti-biofilm potential against Vibrio alginolyticus

There is an increasing emergence of antibiotic-resistant Vibrio alginolyticus, a zoonotic pathogen that causes mass mortality in aquatic animals and infects humans; therefore, there is a demand for alternatives to antibiotics for the treatment and prevention of infections caused by this pathogen. One possibility is through the exploitation of bacteriophages. In the present study, the novel bacteriophage pVa-21 was classified as Myoviridae and characterised as a candidate biocontrol agent against V. alginolyticus. Its morphology, host range and infectivity, growth characteristics, planktonic or biofilm lytic activity, stability under various conditions, and genome were investigated. Its latent period and burst size were estimated to be approximately 70 min and 58 plaque-forming units/cell, respectively. In addition, phage pVa-21 can inhibit bacterial growth in both the planktonic and biofilm states. Furthermore, phylogenetic and genome analysis revealed that the phage is closely related to the giant phiKZ-like phages and can be classified as a new member of the phiKZ-like bacteriophages that infect bacteria belonging to the family Vibrionaceae.

Phage Therapy as a Promising New Treatment for Lung Infection Caused by Carbapenem-Resistant Acinetobacter baumannii in Mice

Carbapenem-resistant Acinetobacter baumannii (CRAB) which is noted as a major pathogen associated with healthcare-associated infections has steadily developed beyond antibiotic control. Lytic bacteriophages with the characteristics of infecting and lysing specific bacteria have been used as a potential alternative to traditional antibiotics to solve multidrug-resistant bacterial infections. Here, we isolated A. baumannii-specific lytic phages and evaluated their potential therapeutic effect against lung infection caused by CRAB clinical strains. The combined lysis spectrum of four lytic phages' ranges was 87.5% (42 of 48) against CRAB clinical isolates. Genome sequence and analysis indicated that phage SH-Ab15519 is a novel phage which does not contain the virulence or antibiotic resistance genes. In vivo study indicated that phage SH-Ab15519 administered intranasally can effectively rescue mice from lethal A. baumannii lung infection without deleterious side effects. Our work explores the potential use of phages as an alternative therapeutic agent against the lung infection caused by CRAB strains.