Burst Size Research Articles

Isolation, characterization and liposome-loaded encapsulation of a novel virulent Salmonella phage vB-SeS-01

IntroductionSalmonella is a common foodborne pathogenic bacterium, displaying facultative intracellular parasitic behavior, which can help the escape against antibiotics treatment. Bacteriophages have the potential to control both intracellular and facultative intracellular bacteria and can be developed as antibiotic alternatives.MethodsThis study isolated and characterized vB-SeS-01, a novel Guernseyvirinae phage preying on Salmonella enterica, whose genome is closely related to those of phages SHWT1 and vB-SenS-EnJE1. Furthermore, nine phage-carrying liposome formulations were developed by film hydration method and via liposome extruder.Results and DiscussionPhage vB-SeS-01 displays strong lysis ability against 9 out of 24 tested S. enterica strains (including the pathogenic “Sendai” and “Enteritidis” serovars), high replicability with a burst size of 111 ± 15 PFU/ cell and a titre up to 2.1 × 1011 PFU/mL, and broad pH (4.0 ~ 13.0) and temperature (4 ~ 80°C) stabilities. Among the nine vB-SeS-01 liposome-carrying formulations, the one encapsulated with PC:Chol:T80:SA = 9:1:2:0.5 without sonication displayed the optimal features. This formulation carried up to 1011 PFU/mL, with an encapsulation rate of 80%, an average size of 172.8 nm, and a polydispersity index (PDI) of 0.087. It remained stable at 4°C and 23°C for at least 21 days and at 37°C for 7 days. Both vB-SeS-01 and vB-SeS-01-loaded liposomes displayed intracellular antimicrobial effects and could reduce the transcription level of some tested intracellular inflammatory factors caused by the infected S. enterica sv. Sendai 16,226 and Enteritidis 50041CMCC.

Isolation, characterization and therapeutic efficacy of lytic bacteriophage ZK22 against Salmonella Typhimurium in mice

BackgroundSalmonella enterica serovar Typhimurium is one of the most common serovars of Salmonella associated with clinical cases. It not only leads to diarrhea and mortality raised in livestock and poultry farming, but also poses a risk to food safety.ResultsIn this study, a lytic bacteriophage named ZK22 was isolated and identified from sewage. It exhibited favorable capability against 20 strains of S. Typhimurium. The genome of ZK22 consisted of a double-stranded DNA with a total length of 47,066 base pairs and a GC content of 45.71%. A total of 78 coding sequences were predicted, with no virulence genes or drug resistance genes predicted. Based on blastn similarity analysis, ZK22 belongs to the genus Skatevirus of the class Caudoviricetes, as a long-tailed Siphovirus. Biological characteristics of ZK22 indicated that the optimal multiplicity of infection (MOI) of bacteriophage ZK22 to S. Typhimurium was 10− 2 (PFU/cell), with an incubation period of around 10 min and the burst size of 393 PFU/cell. The physicochemical resistance results of ZK22 demonstrated that it maintained stability under temperatures ranging from 4 °C to 70 °C and under pH conditions ranging from 3 to 12. After inoculating S. Typhimurium at 37 °C, co-culture mixed with the optimal multiplicity of infection exhibited the lowest OD600 within 12 h, demonstrating the exceptional antibacterial effect. Inoculation of phage ZK22 in mice infected with S. Typhimurium was performed to assess its therapeutic efficacy in vivo. The results showed that phage ZK22 at a dose of 108 PFU/mL increased the survival rates of infected mice, effectively suppressed the dissemination and colonization of the host bacteria in the mice, and alleviated the inflammatory response caused by the infection.ConclusionsIn summary, bacteriophage ZK22 presents favorable application prospects as a potential biological agent for the control of Salmonella infections in livestock and poultry farming.

Characterization and genome analysis of a novel phage BP15 infecting Vibrio parahaemolyticus

Vibrio parahaemolyticus is pathogenic to both humans and marine animals. Antimicrobial-resistant (AMR) bacteria have been reported to cause mortalities in shrimp, with phage therapy presenting an alternative and eco-friendly biocontrol strategy for controlling bacterial diseases. Therefore, this study aimed to isolate and characterize phages for their applicability in lysing Vibrio parahaemolyticus. A novel phage vB_VpaS_BP15 (BP15) belonged to the subfamily Queuovirinae with an icosahedral head measuring 69.11 ± 5.38 nm in length and 65.40 ± 6.89 nm in width, and a non-contractile sheathed tail measuring 139.81 ± 14.79 nm. The one-step growth curve indicated a latent period of 30 min and a burst size of 120 PFUs per cell. Phage BP15 exhibited tolerance to a range of temperatures and pH values. Infection dynamic curves demonstrated that BP15 was highly effective against BCRC12959 at MOIs ranging from 0.01 to 10; even at a low multiplicity of infection (MOI) of 0.001, BP15 still caused growth retention. Phage BP15 possessed a circular double-stranded DNA of 59,584 bp with a G + C content of 46.7% and lacked tRNA genes, virulence genes, and lysogeny genes. These findings highlight the promising potential of phage BP15 as a biocontrol agent against Vibrio parahaemolyticus in Taiwan.

A novel broad-spectrum bacteriophage cocktail against methicillin-resistant Staphylococcus aureus: Isolation, characterization, and therapeutic potential in a mastitis mouse model.

Bovine mastitis is a considerable challenge within the dairy industry, causing significant financial losses and threatening public health. The increased occurrence of methicillin-resistant Staphylococcus aureus (MRSA) has provoked difficulties in managing bovine mastitis. Bacteriophage therapy presents a novel treatment strategy to combat MRSA infections, emerging as a possible substitute for antibiotics. This study evaluated the therapeutic potency of a novel bacteriophage cocktail against MRSA mastitis. Two new bacteriophages (vB_SauR_SW21 and vB_SauR_SW25) with potent lytic activity against MRSA were isolated and characterized. The one-step growth curve displayed a rapid latent period (20-35 min) and substantial burst size (418 and 316 PFU/ cell). In silico analyses have confirmed the absence of antimicrobial resistance or virulence factor-encoding genes within their genomes. According to the results, combining these phages augmented their host range and virulence. The phage cocktail significantly reduced bacterial burden in a BALB/c mastitis model, demonstrating efficacy comparable to antibiotic treatment. Moreover, its administration led to decreased concentrations of IL-1β and TNF-α compared to the negative control group. The bacteriophage cocktail (SW21-SW25) exhibits a promising profile for therapeutic applications and may represent a novel substitute to antibiotics for managing MRSA bovine mastitis.

Characterization of Broad Spectrum Bacteriophage vB ESM-pEJ01 and Its Antimicrobial Efficacy Against Shiga Toxin-Producing Escherichia coli in Green Juice.

Shiga toxin-producing Escherichia coli (STEC) infections have increased in humans, animals, and the food industry, with ready-to-eat (RTE) food products being particularly susceptible to contamination. The prevalence of multidrug-resistant strains has rendered the current control strategies insufficient to effectively control STEC infections. Herein, we characterized the newly isolated STEC phage vB_ESM-pEJ01, a polyvalent phage capable of infecting Escherichia and Salmonella species, and assessed its efficacy in reducing STEC in vitro and food matrices. The phage, belonging to the Tevenvirinae, exhibits effective bacteriolytic activity, a short latent period, large burst size, and stability under a broad pH range and moderate temperatures. Moreover, the phage demonstrated strong anti-biofilm efficacy even at low concentrations. Genomic analysis revealed that the phage was similar to the well-characterized RB49 phage (T4-like phage) but possesses distinct host-specificity-related genes that potentially contribute to its extensive host range. The efficacy of phage vB_ESM-pEJ01 was evaluated in artificially STEC-inoculated green juice samples, where it significantly reduced STEC and the abundance of Shiga toxin-producing genes at 4 and 25 °C. Therefore, these results suggest that the polyvalent phage vB_ESM-pEJ01 is a promising biocontrol agent for foodborne pathogens in RTE foods such as fresh juices.

From Isolation to Application: Utilising Phage-Antibiotic Synergy in Murine Bacteremia Model to Combat Multidrug-Resistant Enterococcus faecalis.

Enterococcus species, natural inhabitants of the human gut, have become major causes of life-threatening bloodstream infections (BSIs) and the third most frequent cause of hospital-acquired bacteremia. The rise of high-level gentamicin resistance (HLGR) in enterococcal isolates complicates treatment and revives bacteriophage therapy. This study isolated and identified forty E. faecalis clinical isolates, with 30% exhibiting HLGR. The HLGR5 isolate, resistant to fosfomycin, vancomycin, and linezolid, was used to isolate the vB_EfaS_SZ1 phage from effluent water. This phage specifically lysed 42% of HLGR isolates. vB_EfaS_SZ1 demonstrated beneficial traits, including thermal stability, acid-base tolerance, a short latent period, and a large burst size. The phage genome comprises a 40,942 bp linear double-stranded DNA with 65 open reading frames (ORFs). The genome closely resembled Enterococcus phages, classifying it within the Efquatrovirus genus. Phage-antibiotic synergy was assessed using checkerboard assays and time-killing analyses, revealing enhanced bacteriolytic activity of ampicillin and fosfomycin, with significant reductions in minimum inhibitory concentration values. In a mouse bacteremia model, phage-antibiotic combinations significantly reduced E. faecalis liver burden compared to monotherapies. Histopathological analysis confirmed therapeutic synergy, showing reduced inflammation and improved hepatocyte regeneration. These findings underscore the potential of phage vB_EfaS_SZ1 as an adjunct to antibiotic therapy for resistant enterococcal bacteremia.

The Combination of Phage Therapy and β-Lactam Antibiotics for the Effective Treatment of Enterococcus faecalis Infections

A phage–antibiotic synergy could be an alternative in urinary tract infection (UTI) therapy, as it leads to the elimination of bacteria and to the reduction in variants resistant to phages and antibiotics. The aims of the in vitro study were to determine whether phages vB_Efa29212_2e and vB_Efa29212_3e interact synergistically with selected antibiotics in the treatment of E. faecalis infections, to optimize antibiotic concentrations and phage titers for the most effective combinations, and to assess their impact on the number of spontaneous resistant variants and on the phages’ reproductive cycles. The modified double-layer disc diffusion method, checkboard, time–kill assays, one-step growth method and the double agar overlay plaque assay were implemented. Synergistic interactions were most often observed after the combined action of phages 2e or 3e and β-lactam antibiotics on E. faecalis strains. The beneficial effects depended on the bacterial strain, phage and antibiotic used. The lowest minimum inhibitory concentration (MIC50) values of the antibiotics were recorded, after the application of low titers of phage 2e, and high titers of phage 3e. The combined use of the tested agents resulted in a significant reduction in the number of resistant variants and had an impact on the reproductive cycle of the tested phages, e.g., a 50% increase in burst size, and a 5 min reduction in the latency period of 2e were observed. The study confirmed beneficial interactions between phages and β-lactam antibiotics against E. faecalis growth.

Characterization and genomic analysis of Salmonella Abortusequi phage, vB_SalP_LDDK01, and its biocontrol application in donkey meat

Salmonella Abortusequi (S. Abortusequi) is the primary cause of abortions in equine animals, and can cause serious foodborne illness. Thus, effective biocontrol strategies are needed to decontaminate and control the emergence of foodborne diseases. In recent years, phages have been used as a new strategy for modulating foodborne pathogens and food safety. In this study, a new phage, vB_SalP_LDDK01, was isolated from donkey farm bedding. The data indicated that the incubation period of vB_SalP_LDDK01 was 10 min, the burst size was 378 PFU/cell, as well as a wide range of heat resistance (40-70°C) and pH stability (4-12). Furthermore, genomic analysis and electron microscopy indicated that vB_SalP_LDDK01 belongs to the Class Caudoviricetes and genus Jerseyvirus. Moreover, its genome was 42,378 bp long, encoded 57 ORFs, was double-stranded DNA with a 49.52% GC content, and lacked virulence and drug-resistant genes. In addition, how vB_SalP_LDDK01 inhibits the growth of S. Abortusequi and removes the biofilm of S. Abortusequi was assessed in a liquid broth medium, and the results showed that vB_SalP_LDDK01 inhibited the growth of S. Abortusequi for about 8 h and significantly reduced the viable bacteria abundance compared with the phage-free positive control. Further, vB_SalP_LDDK01 treated the host bacteria for 12 h and effectively destroyed the biofilm of S. Abortusequi. This study further investigated how effectively vB_SalP_LDDK01 modulates bacterial contamination in donkey meat inoculated with S. Abortusequi LCU-S-ABORT-F at 4°C and 25°C. Furthermore, after 72 h of vB_SalP_LDDK01 treatment with different multiplicity of infection (1, 0.1, 0.01, and 0.001), the bacterial contamination on the surface of donkey meat was reduced by 4.3, 3.7, 3.3, and 3.5 log10 CFU/piece at 25°C, and 4.5, 3.9, 2.8, and 2.7 log10 CFU/piece at 4°C. Whereas the phage titers at different temperatures were basically comparable to the initial titers. Overall, these results indicated that vB_SalP_LDDK01, the new phage, can serve as an effective biological agent and inhibit S. Abortusequi in donkey meat.

Molecular characterization and safety properties of multi drug-resistant Escherichia coli O157:H7 bacteriophages

The increase in multi drug resistance (MDR) amongst food-borne pathogens such as Escherichia coli O157:H7, coupled with the upsurge of food-borne infections caused by these pathogens is a major public health concern. Lytic phages have been employed as an alternative to antibiotics for use against food-borne pathogens. However, for effective application, phages should be selectively toxic. Therefore, the objective of this study was to characterise lytic E. coli O157:H7 phages isolated from wastewater as possible biocontrol agents and access their genomes for the absence of genes that denotes virulence, resistance, toxins, and lysogeny using whole genome sequencing. E. coli O157:H7 bacteriophages showed clear plaques ranging in size from 1.0 mm to 2.0 mm. Spot test and Efficiency of plating (EOP) analysis demonstrated that isolated phages could infect various environmental E. coli strains. Four phages; vB_EcoM_EP32a, vB_EcoP_EP32b, vB_EcoM_EP57, and vB_EcoM_EP69 demonstrated broad lytic spectra against E. coli O157:H7 strains. Transmission Electron Microscopy (TEM) showed that all phages have tails and were classified as Caudoviricetes. Growth parameters showed an average latent period of 15 ± 3.8 min, with a maximum burst size of 392 PFU/cell. The phages were stable at three distinct temperatures (4 °C, 28 °C, and 37 °C) and at pH values of 3.5, 5.0, 7.0, 9.0, and 11.0. Based on their morphological distinctiveness, three phages were included in the Whole Genome Sequencing (WGS) analysis. WGS results revealed that E. coli O157:H7 phages (vB_EcoM_EP32a, vB_EcoP_EP32b, and vB_EcoM_EP57) were composed of linear double-stranded DNA (dsDNA) with genome sizes 163,906, 156,698, and 130,723 bp and GC contents of 37.61, 37, and 39% respectively. Phages vB_EcoM_EP32a and vB_EcoP_EP32b genomes were classified under the class Caudoviricetes, Straboviridae family, and the new genus “Phapecoctavirus”, while vB_EcoM_EP57 was classified under the class Caudoviricetes, Autographiviridae family. Genome analysis revealed no lysogenic (integrase), virulence, or antimicrobial resistance sequences in all three Escherichia phage genomes. The overall results provided evidence that lytic E. coli O157:H7 bacteriophages in this study, are relatively stable, can infect diverse E. coli strains, and does not contain genes responsible for virulence, resistance, toxins, and lysogeny. Thus, they can be considered as biocontrol candidates against MDR pathogenic E. coli O157:H7 strains in the food industry.

Host-specific viral predation network on coral reefs.

Viral infections are major modulators of marine microbial community assembly and biogeochemical cycling. In coral reefs, viral lysis controls bacterial overgrowth that is detrimental to coral health. However, methodological limitations have prevented the identification of viral hosts and quantification of their interaction frequencies. Here, we reconstructed an abundance-resolved virus-bacteria interaction network in the oligotrophic coral reef waters of Curaçao by integrating direct microscopy counts with virus-host links obtained from proximity-ligation, prophage integration, and CRISPR spacers. This network of 3,013 individual links (97 unique species-level interactions) revealed that the abundance of free viral particles was weakly related to host abundance and viral production, as indicated by the cell-associated virus-to-host ratio. The viruses with the highest free and cell-associated virus-to-host ratio, interpreted here as highly productive viruses, formed links with intermediate-to-low abundance hosts belonging to Gammaproteobacteria, Bacteroidia, and Planctomycetia. In contrast, low-production viruses interacted with abundant members of Alphaproteobacteria and Gammaproteobacteria enriched in prophages. These findings highlight the decoupling between viral abundance and production and identify potentially active viruses. We propose that differential decay rates and burst sizes may explain the decoupling between free viral abundance and production and that lysogenic infections play an important role in the ecology of high-abundance hosts.

Isolation, partial characterization, therapeutic, and safety evaluation of carbapenem-resistant Acinetobacter baumannii lytic phage in a mouse model

BackgroundAntimicrobial resistance (AMR) is a major worldwide health concern, characterized by the ability of microorganisms to withstand the effects of medications that once effectively treated infections. Phage therapy has emerged as a promising alternative for management of multidrug-resistant (MDR) bacterial infections. Acinetobacter baumannii (A. baumannii) exemplifies the emergence of bacteria resistant to clinically relevant antimicrobials, leading to severe nosocomial infections and exhibiting extensive and pan drug-resistant (XDR and PDR) traits. In response, this study isolated A. baumannii virulent phage designated as vB_AbaP_PhE54 against carbapenem-resistant A. baumannii (CRAB) pathogen and examined its morphological characteristics using an electron micrograph. Phage stability at different temperatures, pH, chloroform, safety, therapeutic evaluation, and growth kinetics have been analyzed.ResultsThe A. baumannii phage vB_AbaP_PhE54 belongs morphologically to the Podoviridae family with very short, noncontractile tails, the phage demonstrated high thermal tolerance and infectivity across a pH range of 4–11, although it displayed a narrow host range. One-step growth kinetics indicated a burst size of 85 PFU (Plaque Forming Unit) per infected cell and a latent period of 20 min. Additionally, therapeutic efficiency in a mouse model showed total elimination of CRAB pathogen from lungs homogenates of mice and recovery from lung inflammation in all infected mice. On the other hand, safety evaluation of isolated phage revealed no adverse effects on structural or morphological tissue integrity.ConclusionsThese findings suggest that A. baumannii phage vB_AbaP_PhE54 could be a viable safe therapeutic option against A. baumannii infections, warranting further research into its clinical applications.

Characterization of a Salmonella abortus equi phage 4FS1 and its depolymerase.

The significant economic losses caused by S. abortus equi in donkey husbandry have increased interest in exploring the potential of phages and their enzymes as control strategies. In this study, a S. abortus equi phage, designated 4FS1, was isolated from sewage at a donkey farm. Transmission electron microscopy (TEM) revealed a typical icosahedral head and a long, non-contractile tail. It exhibited a short latent period of 20 min and a burst size of 160 plaque-forming units (PFU) per cell. It demonstrated a broad host range, infecting 36 out of 60 salmonella strains, with an optimal multiplicity of infection (MOI) of 0.01 for S. abortus equi S1. The phage titer remained stable at 109 PFU/mL between 37°C and 50°C and exceeded 108 PFU/mL at pH from 5.0 to 10.0. After 1 h of UV exposure, the titer remained at 107 PFU/mL and showed no significant variation across NaCl concentrations from 2.5 to 15%. The genome of phage 4FS1 consists of a 42,485 bp linear double-stranded DNA molecule with a G + C content of 49.07%. Of the 56 predicted open reading frames (ORFs), 32 were functional annotated, with no virulence or drug resistance genes identified. ORF36 was predicted to encode a depolymerase responsible for endorhamnosidase activity. Recombinant expression of the Dpo36 protein in prokaryotes significantly reduced biofilm formation and removal. Combined with healthy donkey serum, Dpo36 inhibited bacterial growth in vitro and enhanced the survival rates of mice infected with S. abortus equi. These findings highlight the promising potential of phages and their depolymerases as novel therapeutic agents against S. abortus equi.

Optimisation of gene expression noise for cellular persistence against lethal events

Bacterial cell persistence, crucial for survival under adverse conditions like antibiotic exposure, is intrinsically linked to stochastic fluctuations in gene expression. Certain genes, while inhibiting growth under normal circumstances, confer tolerance to antibiotics at elevated expression levels. The occurrence of antibiotic events lead to instantaneous cellular responses with varied survival probabilities correlated with gene expression levels. Notably, cells with lower protein concentrations face higher mortality rates. This study aims to elucidate an optimal strategy for protein expression conducive to cellular survival. Through comprehensive mathematical analysis, we determine the optimal burst size and frequency that maximise cell proliferation. Furthermore, we explore how the optimal expression distribution changes as the cost of protein expression to growth escalates. Our model reveals a hysteresis phenomenon, characterised by discontinuous transitions between deterministic and stochastic optima. Intriguingly, stochastic optima possess a noise floor, representing the minimal level of fluctuations essential for optimal cellular resilience.

Phage cocktail amikacin combination as a potential therapy for bacteremia associated with carbapenemase producing colistin resistant Klebsiella pneumoniae

The increasing occurrence of hospital-associated infections, particularly bacteremia, caused by extensively drug-resistant (XDR) carbapenemase-producing colistin-resistant Klebsiella pneumoniae highlights a critical requirement to discover new therapeutic alternatives. Bacteriophages having host-specific bacteriolytic effects are promising alternatives for combating these pathogens. Among 12 phages isolated from public wastewater in Thailand, two phages-vB_kpnM_05 (myovirus) and vB_kpnP_08 (podovirus) showed broad-host range, producing bacteriolytic activities against 81.3% (n = 26) and 78.1% (n = 25) of 32 XDR carbapenemase-producing colistin-resistant K. pneumoniae, with capsular types—K15, K17, K50, K51, K52/wzi-50 and K2/wzi-2. Both phages showed short replication times, large burst sizes with rapid adsorptions. They exhibited significant stability under various environmental conditions. Genomic analysis revealed that both phages are genetically distinct phages from Myoviridae and Podoviridae family, with the lack of toxin, virulence, lysogeny and antibiotic resistance genes. These characteristics highlighted their promising potential for utilizing in phage therapy for combating XDR K. pneumoniae. Although phage cocktail combining vB_kpnM_05 and vB_kpnP_08 provided significant bacteriolysis for longer duration (8 h) than its monophage (6 h), bacterial regrowth was observed which suggested an evitable development of phage resistance under phages’ selection pressures. Future study will be undertaken to elucidate the precise mechanisms by which these XDR K. pneumoniae developed phage resistance and their associated fitness cost. Remarkably, combining phage cocktail with amikacin at their sub-inhibitory concentrations produced potent synergy by completely suppressing bacterial regrowth in vitro. Our study demonstrated the significant therapeutic and prophylactic effectiveness of a phage cocktail-amikacin combination as a promising alternative strategy for overcoming bacteremia associated with XDR K. pneumoniae having carbapenemase and colistin resistance in vivo.

Isolation and Characterization of a Lytic Phage PaTJ Against Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a major global threat to human health, and phage therapy has emerged as a promising strategy for treating infections caused by multidrug-resistant pathogens. In this study, we isolated and characterized a Pseudomonas lytic phage, PaTJ, from wastewater. PaTJ belongs to the phage family Mesyanzhinovviridae, and is featured by short latency (30 min) and large burst size (103 PFU per infected cell). Our investigation revealed that PaTJ utilizes the type IV Pili (T4P) as a receptor. Transcriptome analysis of PaTJ infected host at latent stage showed distinct expression patterns of PaTJ encoding genes involved in replication and structure assembly, without expression of the majority of toxic accessory genes responsible for phage release. In addition, host bacteria exhibited specific induction of host metabolism-related genes in response to the PaTJ's infection. Furthermore, our findings demonstrated the PaTJ's potential in degrading biofilms. This work sheds light on the multifaceted impact of this lytic phage PaTJ on P. aeruginosa, presenting potential applications in both gene expression modulation and biofilm management.

Characterization of two Campylobacter jejuni phages and evaluation of their antibacterial efficacy with EDTA.

Campylobacter jejuni is a leading cause of foodborne illness worldwide. The application of bacteriophages offers a promising approach to specifically target and reduce C. jejuni contamination in food products. In this study, two C. jejuni phages were characterized, and their ability to inhibit bacterial growth in combination with ethylenediaminetetraacetic acid (EDTA) was investigated. Both phages exhibited tolerance to a wide range of temperature (4-60°C) and pH (3-9). Phage vB_CjeM-PC10 and vB_CjeM-PC22 were found to have a latent period of 30 min and 20 min and a burst size of 7 and 35 PFU/cell, respectively. Phage vB_CjeM-PC10 has a linear double-stranded DNA (dsDNA) genome of 51,148 bp with 77 ORFs and 29% GC content. Phage vB_CjeM-PC22 has a circular dsDNA genome of 32,543 bp with 56 ORFs and 28% GC content. At 42°C, the combination of these phages (MOI = 10) and EDTA decreased the count of viable C. jejuni by 5.2 log10 and inhibited the regrowth of resistant cells for 48 h. At 4°C, phage vB_CjeM-PC10 alone (MOI = 1000) reduced the count of viable C. jejuni by 3 log10 in brain heart infusion (BHI) broth and 2 log10 on chicken skin after incubation for 48 h. Although these phages were effective against C. jejuni, they cannot be utilized directly for food safety applications because they are lysogenic. Nevertheless, these findings expand the genome library of C. jejuni phages and enrich data resources by highlighting potential strategies for controlling C. jejuni infections.

A novel Alteromonas phage with tail fiber containing six potential iron-binding domains.

Viruses play a vital role in regulating microbial communities, contributing to biogeochemical cycles of carbon, nitrogen, and essential metals. Alteromonas is widespread and plays an essential role in marine microbial ecology. However, there is limited knowledge about the interactions of Alteromonas and its viruses (alterophages). This study isolated a novel podovirus, vB_AmeP-R22Y (R22Y), which infects Alteromonas marina SW-47 (T). Phylogenetic analysis suggested that R22Y represented a novel viral genus within the Schitoviridae family. R22Y exhibited a broad host range and a relatively large burst size, exerting an important impact on the adaptability and dynamics of host populations. Two auxiliary metabolic genes, encoding Acyl carrier protein and AAA domain-containing protein, were predicted in R22Y, which may potentially assist in host fatty acid metabolism and VB12 biosynthesis, respectively. Remarkably, the prediction of the R22Y tail fiber structure revealed six conserved histidine residues (HxH motifs) that could potentially bind iron ions, suggesting that alterophages may function as organic iron-binding ligands in the marine environment. Our isolation and characterization of R22Y complements the Trojan Horse hypothesis, proposes the possible role of alterophages for marine iron biogeochemical cycling, and provides new insights into phage-host interactions in the iron-limited ocean.IMPORTANCEIron (Fe), as an essential micronutrient, is often a limiting factor for microbial growth in marine ecosystems. The Trojan Horse hypothesis suggests that iron in the phage tail fibers is recognized by the host's siderophore-bound iron receptor, enabling the phage to attach and initiate infection. The potential role of phages as iron-binding ligands has significant implications for oceanic trace metal biogeochemistry. In this study, we isolated a new phage R22Y with the potential to bind iron ions, using Alteromonas, a major siderophore producer, as the host. The tail fiber structure of R22Y exhibits six conserved HxH motifs, suggesting that each phage could potentially bind up to 36 iron ions. R22Y may contribute to colloidal organically complexed dissolved iron in the marine environment. This finding provides further insights into the Trojan Horse hypothesis, suggesting that alterophages may act as natural iron-binding ligands in the marine environment.

Characterization and genomic analysis of bacteriophage VT223 infecting Salmonella enterica subsp enterica serovar Enteritidis

Bacteriophages are increasingly considered a promising alternative to antibiotics for treating bacterial infections. For the bacteriophage VT223, which was isolated from shrimp pond wastewater, a thorough analysis of its host range, morphology, and genome sequencing was performed. Bacteriophage VT223 exhibits high specificity towards Salmonella spp. strains, highlighting its potential as a targeted therapy for Salmonella spp. infections. Electron microscopy revealed that VT223 belongs to the Caudoviricetes, Jerseyvirus, with an icosahedral head and a non-contractile tail. This phage can infect three species within the Salmonella spp., with a short latent period of 30 minutes and a burst size of 446 PFU/infected cells. Genome sequencing revealed a 43,062 bp double-stranded DNA genome with a GC content of 49.6%. Stability tests showed that VT223 is stable over various temperatures and pH levels. Biofilm formation inhibition testing revealed that phage VT223 reduced biofilm by up to 57.7% after a four-hour treatment. In vitro studies demonstrated the lytic activity of VT223 against Salmonella enterica subsp enterica serovar Enteritidis ATCC 49223. These findings provide valuable insights into the biological properties of bacteriophage VT223 and its potential use as a biocontrol agent in livestock production and aquaculture to combat bacterial growth. Published on November 15, 2024

Sympathetic transduction to blood pressure in patients with chronic kidney disease.

Patients with chronic kidney disease (CKD) are more than twice as likely to die from a cardiovascular event than those with normal kidney function. Although CKD may increase resting sympathetic activity, quantification of resting sympathetic outflow alone does not account for the ensuing vasoconstriction, and blood pressure (BP) change (i.e., sympathetic transduction). Patients with CKD have been reported to exhibit elevated α-adrenergic receptor sensitivity, which may predispose this population to greater sympathetic transduction. We tested the hypothesis that patients with CKD have augmented sympathetic transduction to BP. In 16 patients with CKD, 17 bodyweight-matched (BWM) controls, and 11 lean controls of a similar age muscle sympathetic nerve activity (MSNA) and beat-to-beat BP were continuously recorded during quiet supine rest. Signal averaging was used to quantify changes in mean arterial pressure (MAP) and total vascular conductance (TVC) following spontaneous bursts of MSNA. Peak increases in MAP following MSNA bursts were not different among patients with CKD and the control groups (CKD: 2.3 ± 1.1mmHg; BWM controls: 2.1 ± 1.0mmHg; lean controls: 1.7 ± 0.9mmHg; P = 0.28). Likewise, nadir reductions in TVC following all bursts of MSNA were not different among patients with CKD and either control group (P = 0.69). Both patients with CKD and controls had graded increases in MAP and decreases in TVC with increasing burst size, which were not different among groups (all P > 0.05). In summary, these data indicate that patients with CKD do not have augmented sympathetic transduction to BP.

Isolation and Characterization of a Novel Escherichia Bacteriophage with Potential to Control Multidrug-Resistant Avian Pathogenic Escherichia coli and Biofilms.

Background/Objectives: Avian pathogenic Escherichia coli (APEC) infection is a significant problem for the global chicken industry, as it decreases animal welfare and is associated with substantial economic losses. Traditionally, APEC infections have been controlled through the use of antibiotics, which has led to an increased prevalence of antibiotic-resistant E. coli. Therefore, developing alternative treatments for APEC infection is crucial. Methods: In this study, an Escherichia phage specific to multidrug-resistant (MDR) APEC, designated as phage vB_EcoP_PW8 (phage vECPW8), was isolated. The morphology, phage adsorption to host cells, one-step growth curve, thermal stability, pH stability, whole-genome sequencing, antibacterial ability, and antibiofilm efficacy of phage vECPW8 were evaluated. Results: The results demonstrated that phage vECPW8 has a Podoviridae morphology and is effective at lysing bacteria. Phage vECPW8 exhibited a high absorption rate to bacterial cells (more than 85% within 10 min) and had a latent period of 20 min, with a burst size of 143 plaque-forming units per cell. Additionally, phage vECPW8 showed good temperature and pH stability. The phage displayed strong antibacterial activity in vitro, and its efficacy in controlling bacteria was confirmed through scanning electron microscopy. Whole-genome sequencing revealed that the phage has a linear genome with 69,579 base pairs. The genome analysis supported the safety of the phage, as no toxin, virulence, or resistance-related genes were detected. Phage vECPW8 was identified as a novel lytic phage in the Gamaleyavirus genus and Schitoviridae family. The phage also demonstrated antibiofilm efficacy by reducing and preventing biofilm formation, as evidenced by biofilm biomass and bacterial cell viability measurements. Conclusions: These results indicate that phage vECPW8 is a promising candidate for the effective treatment of MDR APEC infections in poultry.