Characterization and Genomic Analysis of Novel Vibrio parahaemolyticus Phage vB_VpaP_DE10

Characterization of the novel phage vB_BceP_LY3 and its potential role in controlling Bacillus cereus in milk and rice

Bacillus cereus is a foodborne pathogen that induces vomiting and diarrhea in affected individuals. It exhibits resistance to traditional sterilization methods and has a high contamination rate in dairy products and rice. Therefore, the development of a new food safety controlling strategy is necessary. In this research, we isolated and identified a novel phage named vB_BceP_LY3, which belongs to a new genus of the subfamily Northropvirinae. This phage demonstrates a short latency period and remains stable over a wide range of temperatures (4-60 °C) and pH levels (4-11). The 28,124 bp genome of LY3 does not contain any antibiotic-resistance genes or virulence factors. With regards to its antibacterial properties, LY3 not only effectively inhibits the growth of B. cereus in TSB (tryptic soy broth), but also demonstrates significant inhibitory effects in various food matrices. Specifically, LY3 treatment at 4 °C with a high MOI (MOI = 10,000) can maintain B. cereus levels below the detection limit for up to 24 h in milk. LY3 represents a safe and promising biocontrol agent against B. cereus, possessing long-term antibacterial capabilities and stability.

Isolation and Biological Characteristics of a Novel Phage and Its Application to Control Vibrio Parahaemolyticus in Shellfish Meat

Vibrio parahaemolyticus is a common foodborne pathogenic bacterium. With the overuse of antibiotics, an increasing proportion of drug-resistant strains are emerging, which puts enormous pressure on public health. In this study, a V. parahaemolyticus-specific phage, VP41s3, was isolated. The head length, width, and tail length of the phage were 77.7 nm, 72.2 nm, and 17.5 nm, respectively. It remained active in the temperature range of 30-50°C and pH range of 4-11. The lytic curve of phage VP41s3 showed that the host bacteria did not grow until 11 h under phage treatment at MOI of 1000, indicating that the phage had good bacteriostatic ability. When it was added to shellfish contaminated with V. parahaemolyticus (15°C, 48 h), the number of bacteria in the experimental group was 2.11 log10 CFU/mL lower than that in the control group at 24 h. Furthermore, genomic characterization and phylogenetic analysis indicated that phage VP41s3 was a new member of the Podoviridae family. The genome contained 50 open reading frames (ORFs), in which the ORF19 (thymidine kinase) was an enzyme involved in the pyrimidine salvage pathway, which might lead to the accelerated DNA synthesis efficiency after phage entered into host cells. This study not only contributed to the improvement of phage database and the development of beneficial phage resources but also revealed the potential application of phage VP41s3 in food hygiene and safety.

A novel phagomagnetic separation-ATP bioluminescence (PhMS-BL) for rapid and sensitive detection of viable Vibrio parahaemolyticus in aquatic product

Detection of viable Vibrio parahaemolyticus (V. parahaemolyticus) is a major challenge due to its significant risk to food safety and human health. Herein, we developed a phagomagnetic separation-ATP bioluminescence (PhMS-BL) assay based on phage VPHZ6 for rapid and sensitive detection of viable V. parahaemolyticus. Phage as a recognition element was coupled to magnetic beads to capture and enrich V. parahaemolyticus, shortening detection time and improving method sensitivity. The intracellular ATP released by chemical lysis using CTAB was quantified using firefly fluorescein-adenosine triphosphate bioluminescence system to detect viable bacteria. So, PhMS-BL method was able to detect V. parahaemolyticus in a linear range of 2.3 × 102 to 1.3 × 107 CFU mL-1, with a detection limit of 78 CFU mL-1 within 15 min. It is successfully applied to detect V. parahaemolyticus in spiked lake water, lobster tail meat, and clam meat. The developed detection strategy can rapidly and sensitively detect viable V. parahaemolyticus in food matrixes.

Characterization of a Vibrio parahaemolyticus-targeting lytic bacteriophage SSJ01 and its application in artificial seawater

Vibrio parahaemolyticus is a major foodborne pathogen causing serious illnesses. In this study, a new lytic bacteriophage SSJ01 that infects V. parahaemolyticus was isolated and characterized. It had a short non-contractile tail and belonged to the Caudoviricetes class. It rapidly adsorbed onto host cells, exhibited a short latent period, and has a large burst size. It showed lytic activities under a broad range of temperature (- 18 to 60 °C), pH (5 to 11), and salinity (0 to 6%). It contained 35 open reading frames with a G + C content of 49.16% without toxic or lysogen-forming genes. The MOI of 105 phage-treated group in vitro reduced the target cells up to 3.49-log CFU/mL at 6 °C and 3.47-log CFU/mL at 25 °C, respectively. In aquatic environments (6 and 25 °C), bactericidal activities showed a significant decrease within 2 h. Therefore, the bacteriophage SSJ01 has potential as a biocontrol agent to control V. parahaemolyticus in marine culture.

Phenotypic characterization and genomic analysis of Limosilactobacillus fermentum phage

Limosilactobacillus (L.) fermentum is widely utilized for its beneficial properties, but lysogenic phages can integrate into its genome and can be induced to enter the lysis cycle under certain conditions, thus accomplishing lysis of host cells, resulting in severe economic losses. In this study, a lysogenic phage, LFP03, was induced from L. fermentum IMAU 32510 by UV irradiation for 70 s. The electron microscopy showed that this phage belonged to Caudoviricetes class. Its genome size was 39,556 bp with a GC content of 46.08%, which includes 20 functional proteins. Compared with other L. fermentum phages, the genome of phage LFP03 exhibited deletions, inversions and translocations. Biological analysis showed that its optimal multiplicity of infection was 0.1, with a burst size of 133.5 ± 4.9 PFU/infective cell. Phage LFP03 was sensitive to temperature and pH value, with a survival rate of 48.98% at 50 °C. It could be completely inactivated under pH 2. The adsorption ability of this phage was minimally affected by temperature and pH value, with adsorption rates reaching 80% under all treated conditions. Divalent cations could accelerate phage adsorption, while chloramphenicol expressed little influence. This study might expand the related knowledge of L. fermentum phages, and provide some theoretical basis for improving the stability of related products and establishing phage control measures.

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

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

Characterization and Preliminary Application of a Novel Lytic Vibrio parahaemolyticus Bacteriophage vB_VpaP_SJSY21

Litopenaeus vannamei is one of the most economically significant aquatic species globally. However, the emergence of acute hepatopancreatic necrosis disease (AHPND) in recent years has resulted in substantial losses within the L. vannamei farming industry. Phage therapy holds promise as an effective strategy for preventing and controlling bacterial infections like AHPND, thereby promoting the healthy and sustainable growth of the shrimp aquaculture sector. In this study, a novel and unique Vibrio parahaemolyticus bacteriophage, named vB_VpaP_SJSY21, was successfully isolated from sewage samples. Using transmission electron microscopy, it was observed that phage SJSY21 has an elongated shell. Notably, phage SJSY21 exhibited high infection efficiency, with an optimal multiplicity of infection (MOI) of only 0.01 and a remarkably short latent period of 10 min, resulting in a lysis quantity of 508. Furthermore, phage SJSY21 demonstrated notable heat resistance and the capacity to withstand high temperatures during preservation, thus holding potential for application in phage therapy. Whole-genome sequencing and analysis confirmed that phage SJSY21 has a genome size of 110,776 bp, classifying it as a new member of the short-tailed bacteriophage family. Additionally, cultivation experiments indicated that phage SJSY21 has the potential to enhance the survival of L. vannamei in culture systems, thereby offering innovative prospects for the application of phage therapy in aquaculture.

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.

In Vitro Activity, Stability and Molecular Characterization of Eight Potent Bacteriophages Infecting Carbapenem-Resistant Klebsiella pneumoniae

BACKGROUND

Members of the genus Klebsiella are among the leading microbial pathogens associated with nosocomial infection. The increased incidence of antimicrobial resistance in these species has propelled the need for alternate/combination therapeutic regimens to aid clinical treatment, including bacteriophage therapy. Bacteriophages are considered very safe and effective in treating bacterial infections. In this study, we characterize eight lytic bacteriophages that were previously isolated by our team against carbapenem-resistant Klebsiella pneumoniae.

METHODS

The one-step-growth curves, stability and lytic ability of eight bacteriophages were characterized. Restriction fragment length polymorphism (RFLP), random amplification of polymorphic DNA (RAPD) typing analysis and protein profiling were used to characterize the microbes at the molecular level. Phylogenetic trees of four important proteins were constructed for the two selected bacteriophages.

RESULTS AND CONCLUSIONS

All eight bacteriophages showed high efficiency for reducing bacterial concentration with high stability under different physical and chemical conditions. We found four major protein bands out of at least ten 15-190 KDa bands that were clearly separated by SDS-PAGE, which were assumed to be the major head and tail proteins. The genomes were found to be dsDNA, with sizes of approximately 36-87 Kb. All bacteriophages reduced the optical density of the planktonic K. pneumoniae abruptly, indicating great potential to reduce K. pneumoniae infection. In this study, we have found that tail fiber protein can further distinguished closely related bacteriophages. The characterised bacteriophages showed promising potential as candidates against carbapenem-resistant Klebsiella pneumoniae via bacteriophage therapy.