Isolation and characterization of Brochothrix phage ADU4

Isolation and characterization of a phage against the multidrug-resistant Candida albicans ATCC 10231 strain from raw sewage

The financial cost of resistance to antibiotics is constantly increasing. Viruses are possible substitutes and effective treatments for diseases caused by multidrug-resistant pathogens. The aim of the present study is to isolate a Candida albicans virus from raw sewage and characterize it. Herein, direct and enrichment approaches were used for virus isolation from a raw sewage sample collected from the El-Rahmania wastewater treatment plant, El-Behiera Governorate, Egypt. Using a transmission electron microscope, the viral particle was found to have a hexagonal head with a diameter of approximately 160 nm and a short tail with a length of 87 nm. The virus was treated at different temperature ranges (30-90 °C) for 5, 15, 30, and 60 min. The virus titer was stable at 30 °C, 40 °C, and 50 °C for 5-60 min and partially stable at 60 °C, 70 °C, and 80 °C. The virus kept its activity at a wide range between pH 5-10, while it was completely inactivated in highly acidic (pH < 5) and alkaline (pH > 10) conditions. The effect of osmotic shock on the isolated virus showed 64 % survivability. The effects of five organic solvents on viral particles-chloroform, ethanol, methanol, dimethyl sulfoxide (DMSO), and ethyl acetate-showed 0.7, 1.1, 1.2, 1.4, and 1.7 log10 reductions in initial viral titer, respectively. This study provided new information about the characterization of the virus isolated against Candida albicans, which will be useful for future formulation of a successful therapeutic viral agent against Candida albicans.

Isolation and characterization of virulent bacteriophages and controlling Salmonella Enteritidis biofilms on chicken meat

Salmonella is a prominent zoonotic pathogen that continues to represent a large threat to food safety and public health worldwide. Concurrently, the inappropriate use of antibiotics has led to the development of antibiotic-resistant strains of Salmonella, highlighting the urgent need for new approaches to manage these bacteria. In this context, virulent bacteriophages are increasingly recognized as a potential and effective biological control method against Salmonella. This study identifies two newly isolated virulent Salmonella phages, phage vB_SalD_ABTNLS3 (S3 for short) and phage 2-3 (2-3 for short). Both phages exhibited effectiveness in preventing biofilm formation and reducing biofilm. S3 and 2-3 could maximize the inhibition of more than 70% and 91% of biofilm formation after 48 h of treatment, and maximize the removal of more than 59% and 96% of mature biofilm after 3 h and 5 h, respectively. Based on these, our study assessed the efficacy of 2-3 in controlling Salmonella enterica serotype Enteritidis (SE) on raw chicken meat at 4°C with varying MOIs, including 1, 100, and 10,000. The maximum reduction observed in SE on chicken meat was 1.15 log10 CFU/mL following a 12-h treatment with the 2-3, a significant decrease of more than 92% compared to the initial levels present in the experiment (MOI = 10,000). In conclusion, our phages performed well in controlling biofilm and disinfecting refrigerated food at 4°C, suggesting their potential as biological agents to reduce Salmonella contamination in the food industry.

Degradation of Preformed Gram-Positive and Gram-Negative Bacterial Biofilms Using Disintegrated and Intact Phages

Introduction

Biofilm is a major challenge across several sectors and contributes to serious risks to public health. This study aimed to evaluate the antibiofilm efficacy of disintegrated phages, whose lytic activities have been eliminated, against bacterial biofilms.

Methods

A total of seven lytic phages were disintegrated by sonication and confirmed to have completely lost their lytic activities by the spot test. Subsequently, both the disintegrated and intact phages were tested on the biofilms produced by five different biofilm-producing bacteria. The effects of heat and proteinase K on the ability of disintegrated phages to disrupt biofilms were determined. Moreover, the structural proteins released after the disintegration of phages were screened for their presence of lipase, amylase, protease, and DNase activities. Genome analysis of all the seven phages were screened for the presence of genes encoding proteins with enzymatic activities.

Results

The disintegrated phages showed more effectiveness in degrading the bacterial biofilm when compared with intact phages. The amylase test results were positive for all the seven disintegrated phages tested, confirming the presence of starch-degrading enzymes. Genomic analysis of five phages revealed the presence of genes encoding transglycosylases, amidases, and glycosaminidases, which could contribute to biofilm degradation. However, only four of these proteins were also structural proteins of phages.

Conclusions

Our study demonstrated that disintegrated phages without lytic effects can still possess biofilm degrading ability, probably associated with the enzymatic activities of their structural proteins. This study showed that phages may have activities beyond lytic phage activities exhibited by their structural enzymes.

Application of a novel phage vB_CjeM_WX1 to control Campylobacter jejuni in foods

Campylobacter jejuni is one of the leading causes of human gastroenteritis. Phage biocontrol is recognized as a natural, environmentally friendly technique that effectively targets pathogens in various foods. In this study, a novel C. jejuni phage named vB_CjeM_WX1 (WX1) was isolated from chicken feces. According to the morphology and genomic analysis, the phage belongs to the Eucampyvirinae genus within the subfamily of Caudoviricetes WX1 exhibited favorable physiological characteristics, as it could maintain its activity even under extreme conditions such as high temperatures (70 °C), acidity (pH = 4), alkalinity (pH = 12), NaCl concentration (1000 mM) and was UV-resistant for 50 min. WX1 could lyse 35 strains of C. jejuni, all of which are highly virulent and multi-drug resistant. Among them, 10 strains of C. jejuni exhibit strong biofilm formation, a critical factor in bacterial persistence and resistance to environmental stressors. The lysis rate of WX1 reached up to 47.3 % in 76 strains of C. jejuni. Phage WX1 inhibited the growth of multi-drug resistant, high virulence and strong biofilm C. jejuni 178-2B in NZCYM broth, as well as greatly reduced biofilm formation on stainless-steel, polyethylene surfaces, and glass. Moreover, phage WX1 decreased the number of C. jejuni in chicken skin to below the detection limit within 48 h. Therefore, phage WX1 can be used in food processing environments and poultry farming, both primary production and during slaughter with a great prospect.

Characterization and genomic analysis of PA-56 Pseudomonas phage from Istanbul, Turkey: Antibacterial and antibiofilm efficacy alone and with antibiotics

Phages are ubiquitous in freshwater, seawater, soil, the human body, and sewage water. They are potent biopharmaceuticals against antimicrobial-resistant bacteria and offer a promising alternative for treating infectious diseases. Also, combining phages with antibiotics enhances the antibiotics' efficacy. This study focused on two Pseudomonas aeruginosa phages isolated from lake and sewage water samples and one of them selected for further investigation. Isolated phages PA-56 and PA-18 infected 92 % and 86 % of the tested 25 clinical Pseudomonas aeruginosa strains, respectively. PA-56 with strong activity was chosen for detailed characterization, antimicrobial studies, and genome analysis. Combining PA-56 with ciprofloxacin or meropenem demonstrated phage-antibiotic synergism and increased antibiofilm efficacy. Genome analysis revealed a GC ratio of 54 % and a genome size of 42.761 bp, with no virulence or antibiotic resistance genes. Notably, PA-56 harboured the toxin-antitoxin protein, MazG. Overall, this study suggests that PA-56 holds promise for future applications in industry or medicine.

Advances in the applications of Bacteriophages and phage products against food-contaminating bacteria

Food-contaminating bacteria pose a threat to food safety and the economy by causing foodborne illnesses and spoilage. Bacteriophages, a group of viruses that infect only bacteria, have the potential to control bacteria throughout the "farm-to-fork continuum". Phage application offers several advantages, including targeted action against specific bacterial strains and minimal impact on the natural microflora of food. This review covers multiple aspects of bacteriophages applications in the food industry, including their use as biocontrol and biopreservation agents to fight over 20 different genera of food-contaminating bacteria, reduce cross-contamination and the risk of foodborne diseases, and also to prolong shelf life and preserve freshness. The review also highlights the benefits of using bacteriophages in bioprocesses to selectively inhibit undesirable bacteria, such as substrate competitors and toxin producers, which is particularly valuable in complex microbial bioprocesses where physical or chemical methods become inadequate. Furthermore, the review briefly discusses other uses of bacteriophages in the food industry, such as sanitizing food processing environments and detecting specific bacteria in food products. The review also explores strategies to enhance the effectiveness of phages, such as employing multi-phage cocktails, encapsulated phages, phage products, and synergistic hurdle approaches by combining them with antimicrobials.

Characterization of two virulent Salmonella phages and transient application in egg, meat and lettuce safety

Salmonella, a prominent foodborne pathogen, has posed enduring challenges to the advancement of food safety and global public health. The escalating concern over antibiotic misuse, resulting in the excessive presence of drug residues in animal-derived food products, necessitates urgent exploration of alternative strategies for Salmonella control. Bacteriophages emerge as promising green biocontrol agents against pathogenic bacteria. This study delineates the identification of two novel virulent Salmonella phages, namely phage vB_SalS_ABTNLsp11241 (referred to as sp11241) and phage 8-19 (referred to as 8-19). Both phages exhibited efficient infectivity against Salmonella enterica serotype Enteritidis (SE). Furthermore, this study evaluated the effectiveness of two phages to control SE in three different foods (whole chicken eggs, raw chicken meat, and lettuce) at different MOIs (1, 100, and 10000) at 4°C. It's worth noting that sp11241 and 8-19 achieved complete elimination of SE on eggs after 3 h and 6 h at MOI = 100, and after 2 h and 5 h at MOI = 10000, respectively. After 12 h of treatment with sp11241, a maximum reduction of 3.17 log10 CFU/mL in SE was achieved on raw chicken meat, and a maximum reduction of 3.00 log10 CFU/mL was achieved on lettuce. Phage 8-19 has the same effect on lettuce as sp11241, but is slightly less effective than sp11241 on chicken meat (a maximum 2.69 log10 CFU/mL reduction). In conclusion, sp11241 and 8-19 exhibit considerable potential for controlling Salmonella contamination in food at a low temperature and represent viable candidates as green antibacterial agents for food applications.

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

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

Isolation and characterization of a novel temperate bacteriophage infecting Aeromonas hydrophila isolated from a Macrobrachium rosenbergii larvae pond

Aeromonas hydrophila is an opportunistic pathogen that frequently leads to significant mortality in various commercially cultured aquatic species. Bacteriophages offer an alternative strategy for pathogens elimination. In this study, we isolated, identified, and characterized a novel temperate A. hydrophila phage, designated as P05B. The bacteriophage P05B is a myovirus based on its morphological features, and possesses the capability to lyse A. hydrophila strains isolated from shrimp. The optimal multiplicity of infection (MOI), adsorption rate, latent period, and burst size for phage P05B were determined to be 0.001, 91.7 %, 20 min, and 483 PFU/cell, respectively. Phage P05B displayed stability across a range of temperatures (28-50 °C) and pH values (4.0-10.0). Sequence analysis unveiled that the genome of phage P05B comprises 32,302 base pairs with an average G + C content of 59.4 %. A total of 40 open reading frames (ORF) were encoded within the phage P05B genome. The comparative genomic analyses clearly implied that P05B might represent a novel species of the genus Bielevirus under Peduoviridae family. A phylogenetic tree was reconstructed, demonstrating that P05B shares a close evolutionary relationship with other Aeromonas and Aeromonas phages. In conclusion, this study increased our knowledge about a new temperate phage of A. hydrophila with strong lytic ability.

The characterization and genome analysis of a novel phage phiA034 targeting multiple species of Aeromonas

Aeromonas is one of the most serious pathogens in freshwater aquaculture. Overuse of antibiotics for the treatment of fish diseases has led to the frequent occurrence of drug-resistant strains. Phage therapy is an alternative approach to overcoming the multi-drug resistance associated with antibiotics. In this study, a novel phage phiA034 targeting the host A. veronii A034 was isolated. The phage could infect 14 strains of 4 species Aeromonas. The phage phiA034 displayed head-tail structure with an icosahedral head in the TEM image. At the optimal MOI of 1, it had a latent period of nearly 20 minutes and a burst size of 286 PFU/cell. Besides, the phage phiA034 exhibited high tolerance to a wide range of temperature (30-70 °C) and acid-base (pH 6.0-10.0). The whole genome of phage phiA034 was sequenced with a size of 61,443 bp and annotated with 82 ORFs, mainly related to structure, DNA replication, and lysis. Based on the analysis and comparison of the genomes and proteomes, phage phiA034 could be classified as a novel species of an existing genus Duplodnaviria Heunggongvirae, Uroviricota, Caudoviricetes, Casjensviridae, Sharonstreetvirus. These findings have expanded the species bank and genomes library of bacterial virus and will promote the application of phage therapy in Aeromonas disease.

Environmental DNA transformation resulted in an active phage in Escherichia coli

The achievement of an active biological entity from environmental DNA is important in the field of phage. In this study, the environmental DNA extracted from hospital wastewater was transferred into Escherichia coli DH10B and Escherichia coli BL21 with chemical transformation and electroporation. After transformation, overnight cultures were filtered and used as phage source. The efficacies of the techniques were evaluated with spot test and double-layer agar assay. The emerged phage, named as ADUt, was purified and host-range analysis was performed. Phage DNA was isolated, sequenced and restriction profile was determined. The genome was assembled. The phylogenetic tree was constructed via VipTree. The extracted DNA resulted in active phage by the transformation of E. coli DH10B, but not E. coli BL21. The chemical transformation was found more successful than electroporation. ADUt phage was found to be polyvalent and effective against limited strains of Shigella and Escherichia genera. The phage genome size and GC ratio are 166904 bp and 35.67%, respectively. ADUt is a member of Straboviridae family and Tequatrovirus genus. This is the first study that uses environmental DNA for acquiring active phage, which may be an important source of new phage discovery. The result showed that DNA transformation yields active bacteriophage with both chemical transformation and electroporation.

Isolation and characterization of the new isolated bacteriophage YZU-L1 against Citrobacter freundii from a package-swelling of meat product

Citrobacter freundii is an important foodborne pathogen that can cause urethritis, bacteremia, necrotizing abscess, and meningitis in infants. In this study, a gas-producing isolate from vacuum-packed meat products was identified as C. freundii by 16S rDNA. In addition, a new virulent phage YZU-L1, which could specifically lyse C. freundii, was isolated from sewage samples in Yangzhou. Transmission electron microscopy showed that phage YZU-L1 had a polyhedral head of 73.51 nm in diameter and a long tail of 161.15 nm in length. According to phylogenetic analysis employing the terminase large subunit, phage YZU-L1 belonged to the Demerecviridae family and the Markadamsvirinae subfamily. The burst size was 96 PFU/cell after 30 min of latent period and 90 min of rising period. Phage YZU-L1 could maintain high activity at pH of 4-13, and resist 50 °C for up to 60 min. The complete genome of YZU-L1 was 115,014 bp double-stranded DNA with 39.94% G + C content, encoding 164 open reading frames (ORFs), without genes encoding for virulence, antibiotic resistance, or lysogenicity. Phage YZU-L1 treatment significantly reduced the viable bacterial count of C. freundii in a sterile fish juice model, which is expected to be a natural agent for the biocontrol of C. freundii in foods.

Characterization, genome analysis and antibiofilm efficacy of lytic Proteus phages RP6 and RP7 isolated from university hospital sewage

The crystalline formation of biofilms by Proteus blocks the urine flow which often complicates the health care of catheterized patients. Bacteriophages has been highlighted as a promising tool to control biofilm-mediated bacterial infections. Here, we isolated and characterized two newly isolated lytic phages capable of infecting clinical isolates of P. mirabilis and P. vulgaris. Moreover, insights regarding the biological and molecular characterization were analysed. Both RP6 and RP7 phages showed a Proteus-genus-specific profile, administering no lytic activity against other family of Enterobacteriaceae. The optimal MOI value of the RP6 and RP7 phages were determined as 0.1 and 0.01, respectively. The one-step growth curve showed that RP6 and RP7 phages have a short latent period of 20 min and large burst size of 220-371 PFU/ML per infected host cell. Bacteria growth was reduced immediately after the phages were added, which is shown by the optical density (OD) measurement after 24 hr. Proteus phage RP6 and RP7 were found to eradicate both the planktonic and mature biofilms produced by the Proteus isolates tested. Genome sequence of Proteus phage RP6 was found to be 58,619 bp, and a G-C content of 47%. Also, Proteus phage RP7 genome size was 103,593 bp with G-C ratio of 38.45%. A total of 70 and 172 open reading frame (ORF) was encoded in RP6 and RP7 phage genomes, respectively. Interestingly, there were no tRNA encoded by Proteus phage RP6 genome even though there is a significant G-C content difference between the phage and its host. Additionally, the exhibition of highly lytic activity and absence of virulence and antibiotic-resistant genes in both Proteus RP6 and RP7 phages emphasized that this newly isolated phages are promising for potential therapeutic phages.

Biological and Genomic Characteristics of MaMV-DH01, a Novel Freshwater Myoviridae Cyanophage Strain

The genomic traits of cyanophages and their potential for metabolic reprogramming of the host cell remain unknown due to the limited number of studies on cyanophage isolates. In the present study, a lytic Microcystis cyanophage, MaMV-DH01, was isolated and identified. MaMV-DH01 has an icosahedral head approximately 100 nm in diameter and a tail 260 nm in length. Its burst size is large, with approximately 145 phage particles/infected cell; it has a latent period of 2 days, and it shows high stability under pH and temperature stresses. Multiple infection (multiplicity of infection [MOI] 0.0001 to 100) results showed that when the MOI was 0.0001, MaMV-DH01 needed a longer time to lyse host cells. Cyanophage MaMV-DH01 has a double-stranded DNA genome of 182,372 bp, with a GC content of 45.35% and 210 predicted open reading frames (ORFs). These ORFs are related to DNA metabolism, structural proteins, lysis, host-derived metabolic genes, and DNA packaging. Phylogenetic trees based on the whole genome and two conserved genes (TerL and capsid) indicate that MaMV-DH01 is clustered with Ma-LMM01 and MaMV-DC, which are independent of other cyanophages. Collinearity analysis showed that the complete genome of MaMV-DH01 was longer than those of Ma-LMM01 and MaMV-DC, with lengths of 20,263 bp and 13,139 bp, respectively. We verified the authenticity of these excess DNA fragments and found that they are involved to various degrees in the MaMV-DH01 transcription process. Map overlays of environmental virus macrogenomic reads onto the MaMV-DH01 genome revealed that viral sequences similar to that of MaMV-DH01 are widespread in the environment. IMPORTANCE A novel freshwater Myoviridae cyanophage strain, MaMV-DH01, was isolated; this strain infects Microcystis aeruginosa FACHB-524, and the biological and genomic characteristics of MaMV-DH01 provide new insights for understanding the mechanism by which cyanophages infect cyanobacterial blooms.

Exploring the Diversity of Biofilm Formation by the Food Spoiler Brochothrix thermosphacta

Brochothrix thermosphacta is considered as a major spoiler of meat and seafood products. This study explores the biofilm formation ability and the biofilm structural diversity of 30 multi-origin B. thermosphacta strains using a set of complementary biofilm assays (biofilm ring test, crystal violet staining, and confocal laser scanning microscopy). Two major groups corresponding to low and high biofilm producers were identified. High biofilm producers presented flat architectures characterized by high surface coverage, high cell biovolume, and high surface area.