Phage Type Research Articles

Induced Native Phage Cocktails for Multi-microbial Activation Syndrome in Treatment-Resistant Illnesses.

The global population is plagued by chronic illnesses of many types due to, in part, the activation of virulence of many latent microbes leading to chronic multi-system illness, stimulating the new term, multi-microbial activation syndrome (MMAS). Treatment-resistant infections across the entire microbial spectrum are now largely untreatable using the previously successful pharmaceutical and natural medicine options. The heavy-handed methods of long-term chemotherapeutic antibiotics, antifungals, and antiviral drugs, whose adverse effects could be worse than the original illness, are presently essentially useless in the long run, as microbes have developed rapid adaptive mutations, becoming drug-resistant. The introduction of induced native phage therapy opened a completely new treatment category that has the potential to complement or replace aggressive drug therapies of many classes. Since its introduction, many advancements have been made to the technology. The most recent development in this new treatment genre is the ability to formulate induced native phage cocktails that use a wide spectrum of induction signatures within the formulation to stimulate various types of beneficial phages already living within the phageome of the body, to target a wide range of pathogenic microbes and associated advantageous physiological targets. The ability to address the MMAS commonly seen in various chronic illnesses simultaneously within the same formulation enables greater clinical outcomes without harm to the microbiome or to the tissues and systems of the body.

Isolation, characterization, and application of a novel Pseudomonas fluorescens phage vB_PF_Y1-MI in contaminated milk.

The food industry has incurred substantial losses from contamination by Pseudomonas fluorescens, emphasizing the critical importance of implementing effective control strategies. Phages are potential sterilizers due to their specific killing abilities and the difficulty bacteria face in developing resistance. However, a significant barrier to their development is the lack of diversity among phage types. In this study, we characterized a novel lytic P. fluorescens phage, named vB_PF_Y1-MI. Phage vB_PF_Y1-MI displayed a latent period of nearly 10min and a high burst size of 1493 PFU/cell. This phage showed good activity over a wide range of temperature (up to 70°C) and pH (3-12). The genome of phage vB_PF_Y1-MI spans 93,233bp with a GC content of 45%. It encompasses 174 open-reading frames and 19 tRNA genes, while no lysogeny or virulence-associated genes were detected. Phylogenetic analysis positions it as a novel unassigned evolutionary lineage within the Caudoviricetes class among related dsDNA phages. Our study provides foundational insights into vB_PF_Y1-MI and emphasizes its potential as an effective biological control agent against P. fluorescens. This research offers crucial theoretical groundwork and technical support for subsequent efforts in preventing and controlling P. fluorescens contamination.

Making waves: Intelligent phage cocktail design, a pathway to precise microbial control in water systems

Current practices in water and wastewater treatment to control unwanted microbes have led to new problems, including health effects from disinfection byproducts, growth of opportunistic pathogens resistant to residual disinfectants (e.g., chlorine), and antibiotic resistance. These challenges are spurring interest in rethinking our practices of microbial control. Simultaneously, advances in molecular biology and computation power are driving renewed interest in using phages (viruses that infect bacteria) to precisely control microbial growth (aka, phage biocontrol). In this Making Waves article, I begin by reviewing the current state of research into phage cocktail design, emphasizing our limited understanding of the features of successful phage cocktails (combinations of multiple types of phages). I describe the state of modeling phage-bacteria interactions and underscore the need for increasing research efforts to predict phage cocktail success, a key gap slowing the application of phage biocontrol. I also detail how research must also focus on techniques for engineering more effective phages to offer a more rapid alternative to phage discovery from natural environments. In this way, phage cocktails comprised of phages with complementary infection strategies may be designed. The final area for increased research effort that I highlight is the need for phage cocktail design to account for possible unintended environmental effects, a risk that is increasingly acknowledged in phage ecology studies but mostly ignored by those developing phage biocontrol technologies. By focusing more research effort towards the areas necessary for intelligent phage cocktail design, we can accelerate the development of phage-based biocontrol in water systems and improve public health.

Genomic surveillance as a scalable framework for precision phage therapy against antibiotic-resistant pathogens

Phage therapy is gaining increasing interest in the fight against critically antibiotic-resistant nosocomial pathogens. However, the narrow host range of bacteriophages hampers the development of broadly effective phage therapeutics and demands precision approaches. Here, we combine large-scale phylogeographic analysis with high-throughput phage typing to guide the development of precision phage cocktails targeting carbapenem-resistant Acinetobacter baumannii, a top-priority pathogen. Our analysis reveals that a few strain types dominate infections in each world region, with their geographical distribution remaining stable within 6 years. As we demonstrate in Eastern Europe, this spatiotemporal distribution enables preemptive preparation of region-specific phage collections that target most local infections. Finally, we showcase the efficacy of phage cocktails against prevalent strain types using invitro and animal infection models. Ultimately, genomic surveillance identifies patients benefiting from the same phages across geographical scales, thus providing a scalable framework for precision phage therapy.

Aerosolic Application of Phages Against S. infantis on Plates and Chicken Skin.

Phages are known as a promising method to combat antimicrobial resistance (AMR) in the human and veterinary sector. Use of phage aerosols enormously increases the application field, although the impact on the infectivity of phages during nebulization needs to be evaluated. In this study S. infantis was treated on plates and chicken skin with nebulized phage particles of the Myoviridae type, identified by transmission electron microscopy, using a commercial nebulizer primarily used for H2O2 disinfection. The reduction of bacterial number by aerosol applied phage particles was evaluated. It could clearly be shown that the phage particles were able to infect Salmonella after being nebulized using ultrasound technology. Further studies on other types of phages as well as other conditions must be performed to standardize the aerosolic application of phages.

Viral adaptations to alternative hosts in the honey bee pathogen Paenibacillus larvae.

Bacteriophages (phages) that are intended to be used to treat bacterial infections are often improved using genetic engineering or experimental evolution. A protocol called "Appelmans" utilizes evolution in microtiter plates to promote the evolution of phages that can infect nonpermissive hosts. We tested a modification of the Appelmans protocol using the honey bee pathogen, Paenibacillus larvae. Three phages evolved together on four P. larvae strains following the standard Appelmans protocol and a modified version to ensure high phage diversity throughout ten rounds of passaging. The host range of 360 plaques were characterized and six new phage lysis patterns were identified. These new phage lysis patterns included plaque formation on previously nonpermissive, phage-resistant isolates that were used to identify phage types. The modified protocol did not drastically change the rate or number of new phage types observed but did prevent the phage population from being dominated by one phage that tended to rapidly raise in frequency. These findings showed how a minor modification of the Appelmans protocol influenced the development of phages for phage therapy. The method also provided improved phages for the treatment of bacterial infections in honey bees.

CrAss-like phages are suitable indicators of antibiotic resistance genes found in abundance in fecally polluted samples

Antibiotic resistance genes (ARGs) have been extensively observed in bacterial DNA, and more recently, in phage particles from various water sources and food items. The pivotal role played by ARG transmission in the proliferation of antibiotic resistance and emergence of new resistant strains calls for a thorough understanding of the underlying mechanisms. The aim of this study was to assess the suitability of the prototypical p-crAssphage, a proposed indicator of human fecal contamination, and the recently isolated crAssBcn phages, both belonging to the Crassvirales group, as potential indicators of ARGs. These crAss-like phages were evaluated alongside specific ARGs (blaTEM, blaCTX-M-1, blaCTX-M-9, blaVIM, blaOXA-48, qnrA, qnrS, tetW and sul1) within the total DNA and phage DNA fractions in water and food samples containing different levels of fecal pollution. In samples with high fecal load (>103 CFU/g or ml of E. coli or somatic coliphages), such as wastewater and sludge, positive correlations were found between both types of crAss-like phages and ARGs in both DNA fractions. The strongest correlation was observed between sul1 and crAssBcn phages (rho = 0.90) in sludge samples, followed by blaCTX-M-9 and p-crAssphage (rho = 0.86) in sewage samples, both in the phage DNA fraction. The use of crAssphage and crAssBcn as indicators of ARGs, considered to be emerging environmental contaminants of anthropogenic origin, is supported by their close association with the human gut. Monitoring ARGs can help to mitigate their dissemination and prevent the emergence of new resistant bacterial strains, thus safeguarding public health.

Diversity of Shiga toxin transducing phages in Escherichia coli O145:H28 and the different Shiga toxin 2 production levels associated with short- or long-tailed phages.

Shiga toxin (Stx)-producing Escherichia coli (STEC) causes serious gastrointestinal illness, including hemorrhagic colitis and hemolytic uremic syndrome. Two types of Stxs (Stx1 and Stx2) are known and both are encoded by bacteriophages (Stx phages), but the production of Stx2 is known to be a major risk factor for severe STEC infections. The production of Stx2, but not Stx1, is tightly coupled with the induction of Stx phages, and Stx2 production levels vary between STEC strains even within the same serotype. Here, we analyzed the genomic diversity of all Stx phages in 71 strains representing the entire O145:H28 lineage, one of the often highly pathogenic STECs, and the relationship between the variations in Stx phage genomes and the levels of Stx2 production by host strains. Our analysis reveals highly dynamic natures of Stx phages in O145:H28, including the independent acquisition of similar Stx phages by different sublineages, the recent transfer of Stx phage between different sublineages, and the frequent gain and loss of Stx phages in some sublineages. We also show the association of the Stx2 phage types with the Stx2 production levels of host strains: strains carrying short-tailed Stx2 phages exhibited significantly higher Stx2 production levels than those carrying long-tailed Stx2 phages. Detailed analyses of the Stx2 phage genomes revealed that both of short- and long-tailed phages exhibited sequence diversification and they were divided into two groups, respectively, based on the sequence similarity of the phage early region encoding genes responsible for phage induction, short-tailed phages contained early regions clearly different in genetic organization from those in long-tailed phages. Therefore, the variations in the early regions between short-and long-tailed Stx2 phages appeared to be linked to a striking difference in Stx2 production levels in their host strains. These results broaden our understanding of the diversification and dynamism of Stx phages in O145:H28 and the association of Stx2 phage types with the Stx2 production level in this STEC lineage.

Bacteriophages: Natural antimicrobial bioadditives for food preservation in active packaging

Developing innovative films and coatings is paramount for extending the shelf life of numerous food products and augmenting the barrier and antimicrobial properties of food packaging materials. Many synthetic chemicals used in active packaging and food storage have the potential to leach into food, posing long-term health risks. It is imperative for active packaging materials to inherently possess biological protective properties to ensure food quality and safety throughout its storage. Bacteriophages, or simply phages, are bacteria-eating viruses that serve as promising natural biocontrol agents and antimicrobial bioadditives in food packaging materials, specifically targeting bacterial foodborne pathogens. These phages are generally recognized as safe (GRAS) by regulatory authorities for food safety applications. They exhibit targeted action against various Gram-positive and -negative foodborne pathogens, including Bacillus spp., Campylobacter spp., Escherichia coli, Listeria monocytogenes, Salmonella spp., Shigella spp., and Vibrio spp., associated with foodborne spoilage and illness without affecting the beneficial microbes. Phage cocktails can be applied directly on food surfaces, incorporated into food packaging materials, or utilized during food processing treatments. Unlike chemical agents, phage activity increases proportionally with the rise in pathogenic bacterial populations. Researchers are exploring various packaging materials to deliver phages with broad host range, stability, and viability ensuring their effectiveness in safeguarding various food systems. The effectiveness of phage immobilization or encapsulation on active food packaging materials depends on various factors, including the characteristics of polymers, the choice of solvents, the type of phage, and its loading efficiency. Factors such as the orientation of phage immobilization on substrates, pH, temperature, exposure to carbohydrates and amino acids, exopolysaccharides, lipopolysaccharides, and metals can also influence phage activity. In this review, we comprehensively discuss the various active packaging systems utilizing bacteriophages as natural biocontrols and antimicrobial bioadditives to reduce the incidence of foodborne illness and enhance consumer confidence in the safety of food products.

Сучасні підходи до індикації Bacillus anthracis у навколишньому середовищі

Bacillus anthracis — the causative agent of anthrax, which can be used for bioterrorism purposes. An effective biosecurity strategy involves the improvement diagnostics tests for increase its sensitivity and specificity, and the tests for the rapid detection of pathogen. The literature review presents the results of recent methods of detecting Bacillus anthracis spores/cells in environmental objects with greatest epidemiological significance — in air and soil. Conventional microbiological methods are the gold standard for bacterial identification, but their limitation is necessity to cultivate and work with a live particularly dangerous pathogen — B. anthracis, which is associated with the risk of laboratory infection. Now, a number of new methods have been developed for the indication B. anthracis, which allow speed up the process of their detection and are much safer from the point of view of biosecurity. First of all, these are methods based on DNA amplification. Sequencing the DNA of the pathogen adds specificity to the method, and also identifies rare or new variants of B. anthracis. A rapid method for the identification of B. anthracis DNA, which takes less than an hour, has been developed. Also, immunological methods are used to determine the pathogen’s antigen. It should be noted that the specific identification of B. anthracis remains difficult due to its phenotypic and genotypic similarity to other Bacillus species. To solve this problem, a phage typing method was proposed, which has recently been improved with the help of biotechnological methods (construction of the B. anthracis phage) with the detection of its bioluminescence. A promising technology for fast, highly sensitive and specific detection and identification of B. anthracis is biosensor methods using portable devices for their implementation. Key words: anthrax, Bacillus аnthracis, environment, diagnostic tests.

Diverse and abundant phages exploit conjugative plasmids

Phages exert profound evolutionary pressure on bacteria by interacting with receptors on the cell surface to initiate infection. While the majority of phages use chromosomally encoded cell surface structures as receptors, plasmid-dependent phages exploit plasmid-encoded conjugation proteins, making their host range dependent on horizontal transfer of the plasmid. Despite their unique biology and biotechnological significance, only a small number of plasmid-dependent phages have been characterized. Here we systematically search for new plasmid-dependent phages targeting IncP and IncF plasmids using a targeted discovery platform, and find that they are common and abundant in wastewater, and largely unexplored in terms of their genetic diversity. Plasmid-dependent phages are enriched in non-canonical types of phages, and all but one of the 65 phages we isolated were non-tailed, and members of the lipid-containing tectiviruses, ssDNA filamentous phages or ssRNA phages. We show that plasmid-dependent tectiviruses exhibit profound differences in their host range which is associated with variation in the phage holin protein. Despite their relatively high abundance in wastewater, plasmid-dependent tectiviruses are missed by metaviromic analyses, underscoring the continued importance of culture-based phage discovery. Finally, we identify a tailed phage dependent on the IncF plasmid, and find related structural genes in phages that use the orthogonal type 4 pilus as a receptor, highlighting the evolutionarily promiscuous use of these distinct contractile structures by multiple groups of phages. Taken together, these results indicate plasmid-dependent phages play an under-appreciated evolutionary role in constraining horizontal gene transfer via conjugative plasmids.

Structural basis of Acinetobacter type IV pili targeting by an RNA virus

Acinetobacters pose a significant threat to human health, especially those with weakened immune systems. Type IV pili of acinetobacters play crucial roles in virulence and antibiotic resistance. Single-stranded RNA bacteriophages target the bacterial retractile pili, including type IV. Our study delves into the interaction between Acinetobacter phage AP205 and type IV pili. Using cryo-electron microscopy, we solve structures of the AP205 virion with an asymmetric dimer of maturation proteins, the native Acinetobacter type IV pili bearing a distinct post-translational pilin cleavage, and the pili-bound AP205 showing its maturation proteins adapted to pilin modifications, allowing each phage to bind to one or two pili. Leveraging these results, we develop a 20-kilodalton AP205-derived protein scaffold targeting type IV pili in situ, with potential for research and diagnostics.

Assessment of the Nonlinear Electrophoretic Migration of Nanoparticles and Bacteriophages.

Bacteriophage therapy presents a promising avenue for combating antibiotic-resistant bacterial infections. Yet, challenges exist, particularly, the lack of a straightforward purification pipeline suitable for widespread application to many phage types, as some phages are known to undergo significant titer loss when purified via current techniques. Electrokinetic methods offer a potential solution to this hurdle, with nonlinear electrophoresis emerging as a particularly appealing approach due to its ability to discern both the size and shape of the target phage particles. Presented herein is the electrokinetic characterization of the mobility of nonlinear electrophoresis for two phages (SPN3US and ϕKZ) and three types of polystyrene nanoparticles. The latter served as controls and were selected based on their sizes and surface charge magnitude. Particle tracking velocimetry experiments were conducted to characterize the mobility of all five particles included in this study. The results indicated that the selected nanoparticles effectively replicate the migration behavior of the two phages under electric fields. Further, it was found that there is a significant difference in the nonlinear electrophoretic response of phages and that of host cells, as first characterized in a previous report, illustrating that electrokinetic-based separations are feasible. The findings from this work are the first characterization of the behavior of phages under nonlinear electrophoresis effects and illustrate the potential for the development of electrokinetic-based phage purification techniques that could aid the advancement of bacteriophage therapy.

Phages in different habitats and their ability to carry antibiotic resistance genes

As the most abundant organisms on Earth, phages play a key role in the evolution of bacterial antibiotic resistance. Although previous studies have demonstrated the molecular mechanisms of horizontal gene transfer mediated by mobile genetic elements, our understanding of the intertwined relationships between antibiotic resistance genes (ARGs) and phages is limited. In this study, we analysed 2781 metagenomic samples to reveal the composition and species interactions of phage communities in different habitats as well as their capacity to carry ARGs with health risks. The composition of phage communities varies in different habitats and mainly depends on environmental conditions. Terrestrial habitats display more complex and robust interactions between phages than aquatic and human-associated habitats, resulting in the highest biodiversity of phages. Several types of phages in certain taxa (4.95–7.67%, mainly belonging to Caudoviricetes) have the capacity to carry specific ARGs and display a high potential risk to human health, especially in human-associated habitats. Overall, our results provide insights into the assembly mechanisms of phage communities and their effects on the dissemination of antibiotic resistance.

Clean-in-place (CIP) validation of oil-based cleaning and sanitization for Salmonella-contaminated tubing: Evaluation of Enterococcus faecium as a surrogate

The safety of low-moisture foods is of continual concern due to the survival and cross-tolerance of certain bacterial pathogens under dry conditions. This study screened for Salmonella surrogates using a controlled bacterial desiccation system for testing against formulated antimicrobial oils. The effect of inoculum preparation on the heat resistance of Salmonella in peanut butter was also addressed. Thereafter, a tubing system was utilized to validate a dry cleaning and sanitation procedure at the temperature range of peanut butter processing. Tubes were contaminated by re-circulating peanut butter inoculated with a test organism to 108−9 CFU/g. The contaminated system was flushed with fresh canola oil under laminar flow for cleaning, followed by holding with acidified oil or water-in-oil (W/O) emulsion to sanitize. A linear relation (R2, 0.89) was observed between the oil-flush (cleaning) duration and surface cell removal, and the prevailing surface cleanliness dictated the efficacy of sanitization. System decontamination was achieved at 60 °C through a two-step oil flush (3.6 min) and acidified W/O emulsion treatment (30 min). The test organisms, S. Enteritidis phage type 30 and Enterococcus faecium NRRL B-2354, were reduced by this procedure to levels undetectable by enrichment of tubes (n = 9). The E. faecium showed less susceptibility than S. Enteritidis under all the conditions tested, suggesting that it may be used as a Salmonella surrogate to validate such a process in the food-processing environment. Adaptation of the proposed oil-based system would allow a shifted cleaning and sanitation paradigm precluding the necessity of traditional wet cleaning and application of flammable alcohol-based sanitizers.

Complete genome sequence and potential pathogenic assessment of Flavobacterium plurextorum RSG-18 isolated from the gut of Schlegel's black rockfish, Sebastes schlegelii.

Flavobacterium plurextorum is a potential fish pathogen of interest, previously isolated from diseased rainbow trout (Oncorhynchus mykiss) and oomycete-infected chum salmon (Oncorhynchus keta) eggs. We report here the first complete genome sequence of F. plurextorum RSG-18 isolated from the gut of Schlegel's black rockfish (Sebastes schlegelii). The genome of RSG-18 consists of a circular chromosome of 5,610,911 bp with a 33.57% GC content, containing 4858 protein-coding genes, 18 rRNAs, 63 tRNAs and 1 tmRNA. A comparative analysis was conducted on 11 Flavobacterium species previously reported as pathogens or isolated from diseased fish to confirm the potential pathogenicity of RSG-18. In the SEED classification, RSG-18 was found to have 36 genes categorized in 'Virulence, Disease and Defense'. Across all Flavobacterium species, a total of 16 antibiotic resistance genes and 61 putative virulence factors were identified. All species had at least one phage region and type I, III and IX secretion systems. In pan-genomic analysis, core genes consist of genes linked to phages, integrases and matrix-tolerated elements associated with pathology. The complete genome sequence of F. plurextorum RSG-18 will serve as a foundation for future research, enhancing our understanding of Flavobacterium pathogenicity in fish and contributing to the development of effective prevention strategies.

Metagenomic analyses of 7000 to 5500 years old coprolites excavated from the Torihama shell-mound site in the Japanese archipelago.

Coprolites contain various kinds of ancient DNAs derived from gut micro-organisms, viruses, and foods, which can help to determine the gut environment of ancient peoples. Their genomic information should be helpful in elucidating the interaction between hosts and microbes for thousands of years, as well as characterizing the dietary behaviors of ancient people. We performed shotgun metagenomic sequencing on four coprolites excavated from the Torihama shell-mound site in the Japanese archipelago. The coprolites were found in the layers of the Early Jomon period, corresponding stratigraphically to 7000 to 5500 years ago. After shotgun sequencing, we found that a significant number of reads showed homology with known gut microbe, viruses, and food genomes typically found in the feces of modern humans. We detected reads derived from several types of phages and their host bacteria simultaneously, suggesting the coexistence of viruses and their hosts. The food genomes provide biological evidence for the dietary behavior of the Jomon people, consistent with previous archaeological findings. These results indicate that ancient genomic analysis of coprolites is useful for understanding the gut environment and lifestyle of ancient peoples.

The Role of Prophage ϕSa3 in the Adaption of Staphylococcus aureus ST398 Sublineages from Human to Animal Hosts.

Staphylococcus aureus sequence type (ST) 398 is a lineage affecting both humans and livestock worldwide. However, the mechanisms underlying its clonal evolution are still not clearly elucidated. We applied whole-genome sequencing (WGS) typing to 45 S. aureus strains from China and Canada between 2005 and 2014, in order to gain insight into their evolutionary pathway. Based on WGS phylogenetic analysis, 42 isolates were assigned to the human-associated clade (I/II-GOI) and 3 isolates to livestock-associated clade (IIa). Phylogeny of ϕSa3 sequences revealed five phage groups (Groups 1-5), with Group 1 carrying ϕSa3-Group 1 (ϕSa3-G1), Group 2 carrying ϕSa3-G2, Group 3 carrying ϕSa3-G3, Group 4 carrying ϕSa3-G4 and Group 5 lacking ϕSa3. ϕSa3-G1 was only found in strains that accounted for the most ancestral human clade I, while ϕSa3-G2, ϕSa3-G3 and ϕSa3-G4 were found restricted to sublineages within clade II-GOI. Some isolates of clade II-GOI were also found to be ϕSa3-negative or resistant to methicillin which are unusual characteristics for human-adapted isolates. This study demonstrated a strong association between phylogenetic grouping and phage type, suggesting an important role of ϕSa3 prophage in the evolution of human-adapted ST398 subclones. In addition, our results suggest that this subclone slowly began to adapt to animal hosts by losing ϕSa3 and acquiring methicillin resistance, which was observed in some strains of human-associated clade II-GOI, an intermediate human to livestock transmission clade.

Minimal adverse effects of exogenous phage treatment on soil bacterial communities

Bacterial plant pathogens pose significant challenges to global food production, leading to antibiotics and copper being used for their control. Bacteriophages (or phages), which infect bacterial pathogens, have been proposed as an environmentally friendly alternatives for managing these pathogens in crops. However, whether the release of phages into the environment can be considered safe and environmentally friendly has not been well studied. Here, we examined whether the exogenous treatments of various phages with biocontrol potential against Erwinia amylovora, Pectobacterium odoriferum, and Pseudomonas syringae pv. actinidiae impact bacterial communities within soils. To achieve this, five different phages infecting three distinct host bacteria were individually introduced into in soils obtained from an apple orchard, kimchi cabbage field, and a kiwifruit orchard. After one week of phage treatment, soil microbiomes were analyzed using the 16S rRNA gene-based approach. The microbiome analysis results revealed that the phage treatments did not alter the alpha and beta diversities of the bacterial communities, irrespective of the phage types used. Moreover, the overall distribution of microbial taxa remained unaffected by the phage treatment, although slight changes were observed in the abundance of a few taxa. These results indicate that the adverse effects of exogenous phage treatment on soil bacterial communities are minimal, thus the phage treatment in soils can be considered an environmentally friendly strategy.

Evaluation of the impact of repeated intravenous phage doses on mammalian host-phage interactions.

Phage therapy has shown great promise for the treatment of multidrug-resistant bacterial infections. However, the lack of a thorough and organized understanding of phage-body interactions has limited its clinical application. Here, we administered different purified phages (Salmonella phage SE_SZW1, Acinetobacter phage AB_SZ6, and Pseudomonas phage PA_LZ7) intravenously to healthy animals (rats and monkeys) to evaluate the phage-induced host responses and phage pharmacokinetics with different intravenous (IV) doses in healthy animals. The plasma and the organs were sampled after different IV doses to determine the phage biodistribution, phage-induced cytokines, and antibodies. The potential side effects of phages on animals were assessed. A non-compartment model revealed that the plasma phage titer gradually decreased over time following a single dose. Repeated doses resulted in a 2-3 Log10 decline of the plasma phage titer at 5 min compared to the first dose, regardless of the type of phage administered in rats. Host innate immune responses were activated including splenic enlargement following repeated doses. Phage-specific neutralization antibodies in animals receiving phages were detected. Similar results were obtained from monkeys. In conclusion, the mammalian bodies were well-tolerant to the administered phages. The animal responses to the phages and the phage biodistribution profiles could have a significant impact on the efficacy of phage therapy.IMPORTANCEPhage therapy has demonstrated potential in addressing multidrug-resistant bacterial infections. However, an insufficient understanding of phage-host interactions has impeded its broader clinical application. In our study, specific phages were administered intravenously (IV) to both rats and monkeys to elucidate phage-host interactions and evaluate phage pharmacokinetics (PK). Results revealed that with successive IV administrations, there was a decrease in plasma phage concentrations. Concurrently, these administrations elicited both innate and adaptive immune responses in the subjects. Notably, the observed immune responses and PK profiles exhibited variation contingent upon the phage type and the mammalian host. Despite these variations, the tested mammals exhibited a favorable tolerance to the IV-administered phages. This underscores the significance of comprehending these interactions for the optimization of phage therapy outcomes.