A review on re-emerging bacteriophage therapy in the era of XDR

In the present medicine world antibiotic resistance is one of the key threats to universal health coverage.Researchers continue to work hard to combat this global health concern.Phage therapy,an age-old practice during the early twentieth century,was outshined by the discovery of antibiotics.With the advent of widespread antibiotic resistance,phage therapy has again redeemed itself as a potential alternative owing to its adeptness to target bacteria precisely.Limited side effects,the ability to migrate to different body organs,a distinct mode of action,and proliferation at the infection site,make phages a profitable candidate to replace conventional antibiotics.The progressive outcome of numerous in vitro studies and case reports has validated the clinical efficacy of phage therapy.The bright perspective of using phages to treat bacterial infections has fueled enormous medical research to exploit their potential as therapeutics.The gaps in the information about phages and the lack of consent for clinical trials is major hurdle for consideration of phage therapy.Crafting phage therapy as a reality in medicine requires a coordinated effort from different fraternities.With this review,we aim to emphasize the importance of phage therapy in modern medicine.This review explains their historical journey,basic phage biology,cross-talk with the host immunity,obstacles with phage therapy,and their possible remedies.Comprehensive data on the various significant clinical trials of phage therapy has been presented.We evaluated the efficacy of antibiotics and phage therapy in part and in combination,along with recent progress and future perspectives of phage therapy.

Disruption of <i>Mycobacterium smegmatis</i>Biofilms Using Bacteriophages Alone or in Combination with Mechanical Stress

Environmental mycobacteria are capable of forming biofilms in low-nutrient environments, and these biofilms may act as reservoirs for opportunistic infections. The purpose of this study was to determine if bacteriophages could disrupt existing biofilms of acid-fast staining Mycobacterium smegmatis. Using the MBEC 96-well plastic peg assay system, M. smegmatis biofilms were created and then tested for their stability in the presence of mycobacteriophages isolated from a Minnesota sphagnum peat bog. All phages tested were lytic and were observed to have weak, intermediate, and strong abilities to disrupt M. smegmatis biofilms. The formation of biofilms was severely impaired in the presence of mycobacteriophages. Phage treatment was also shown to augment?M. smegmatis biofilm disruption by mechanical forces of sonication or water flow. Our study shows that, as with biofilms of Gram-positive and Gram-negative bacteria, mycobacterial biofilms are also susceptible to destruction by bacteriophages.

Bacteriophage therapy against Enterobacteriaceae

The Enterobacteriaceae are a class of gram-negative facultative anaerobic rods, which can cause a variety of diseases, such as bacteremia, septic arthritis, endocarditis, osteomyelitis, lower respiratory tract infections, skin and soft-tissue infections, urinary tract infections, intra-abdominal infections and ophthalmic infections, in humans, poultry, animals and fish. Disease caused by Enterobacteriaceae cause the deaths of millions of people every year, resulting in enormous economic loss. Drug treatment is a useful and efficient way to control Enterobacteriaceae infections. However, with the abuse of antibiotics, drug resistance has been found in growing number of Enterobacteriaceae infections and, as such, there is an urgent need to find new methods of control. Bacteriophage therapy is an efficient alternative to antibiotics as it employs a different antibacterial mechanism. This paper summarizes the history of bacteriophage therapy, its bacteriallytic mechanisms, and the studies that have focused on Enterobacteriaceae and bacteriophage therapy.

Bacteriophages, revitalized after 100 years in the shadow of antibiotics

The year 2015 marks 100 years since Dr.Frederick Twort discovered the'filterable lytic factor',which was later independently discovered and named 'bacteriophage' by Dr.Felix d’Herelle.On this memorable centennial,it is exciting to see a special issue published by Virologica Sinica on Phages and Therapy.In this issue,readers will not only fi nd that bacteriophage research is

Bacteriophages and their applications in the diagnosis and treatment of hepatitis B virus infection

Hepatitis B virus(HBV) infection is a major global health challenge leading to serious disorders such as cirrhosis and hepatocellular carcinoma. Currently, there exist various diagnostic and therapeutic approaches for HBV infection. However, prevalence and hazardous effects of chronic viral infection heighten the need to develop novel methodologies for the detection and treatment of this infection. Bacteriophages, viruses that specifically infect bacterial cells, with a long-established tradition in molecular biology and biotechnology have recently been introduced as novel tools for the prevention, diagnosis and treatment of HBV infection. Bacteriophages, due to tremendous genetic flexibility, represent potential to undergo a huge variety of surface modifications. This property has been the rationale behind introduction of phage display concept. This powerful approach, together with combinatorial chemistry, has shaped the concept of phage display libraries with diverse applications for the detection and therapy of HBV infection. This review aims to offer an insightful overview of the potential of bacteriophages in the development of helpful prophylactic(vaccine design), diagnostic and therapeutic strategies for HBV infection thereby providing new perspec-tives to the growing field of bacteriophage researches directing towards HBV infection.

Bacteriophages as antimicrobial agents against major pathogens in swine： a review

In recent years, the development of antibiotic resistant bacteria has become a global concern which has prompted research into the development of alternative disease control strategies for the swine industry. Bacteriophages （viruses that infect bacteria） offer the prospect of a sustainable alternative approach against bacterial pathogens with the flexibility of being applied therapeutically or for biological control purposes. This paper reviews the use of phages as an antimicrobial strategy for controlling critical pathogens including Salmonella and Eschefich[a coli with an emphasis on the application of phages for improving performance and nutrient digestibility in swine operations as well as in controlling zoonotic human diseases by reducing the bacterial load spread from pork products to humans through the meat,

Bacteriophage cocktail supplementation improves growth performance,gut microbiome and production traits in broiler chickens

Background:Effective antibiotic alternatives are urgently needed in the poultry industry to control disease outbreaks.Phage therapy mainly utilizes lytic phages to kill their respective bacterial hosts and can be an attractive solution to combating the emergence of antibiotic resistance in livestock.Methods:Five hundred and four,one-day-old broilers(Ross 308)were allotted to 1 of 4 treatment groups in a completely randomized design.Treatments consisted of CON(basal diet),PC(CON+0.025%Avilamax®),BP 0.05(CON+0.05%bacteriophage),and BP 0.10(CON+0.10%bacteriophage).Results:A significant linear effect on body weight gain(BWG)was observed during days 1–7,days 22–35,and cumulatively in bacteriophage(BP)supplemented groups.The BWG tended to be higher(P=0.08)and the feed intake(FI)was increased(P=0.017)in the PC group over CON group.A greater(P=0.016)BWG and trends in increased FI(P=0.06)were observed in the experiment in birds fed PC than CON diet.At the genus level,the relative abundance of Lactobacillus was decreased in PC(65.28%),while it was similar in BP 0.05 and BP 0.10(90.65%,86.72%)compared to CON(90.19%).At the species level,the relative abundance of Lactobacillus salivarus was higher in BP 0.05(40.15%)and BP 0.10(38.58%)compared to the CON(20.04%)and PC(18.05%).A linear reduction in the weight of bursa of Fabricius(P=0.022)and spleen(P=0.052)was observed in birds fed graded level of BP and an increase(P=0.059)in the weight of gizzard was observed in birds fed PC over BP diets.Linear and quadratic responses were observed in redness of breast muscle color in birds fed graded level of BP.Conclusions:The inclusion of the 0.05%and 0.1%BP cocktail linearly improved broiler weight during the first 7 days,22–35 days and cumulatively,whereas 0.05%BP addition was sufficient for supporting immune organs,bursa and spleen as well as enhancing gut microbiome,indicating the efficacy of 0.05%BP as a substitute antibiotic growth promoter in broiler diets.

Complete genome sequence and proteomic analysis of a thermophilic bacteriophage BV1

Viruses of thermophiles are of great interest due to their roles in gene transfer, global geochemical cycle and evolution of life on earth. However, the thermophilic bacteriophages have not been studied extensively. In this investigation, a typical bacteriophage BV1 was obtained from a thermophilic bacterium Geobacillus sp. 6k512, which was isolated from an inshore hot spring in Xiamen of China. The BV1 contained a double-stranded linear DNA of 35 055 bp, which encodes 54 open reading frames （ORFs）. Interestingly, eight of the 54 BV1 ORFs shared sequence similarities to genes from human disease-relevant bacteria. Seven proteins of the purified BV1 virions were identified by proteomic analysis. Determination of BV1 functional genomics would facilitate the better understanding of the mechanism for virus-thermophile interaction.

Compressed wormlike chain moving out of confined space: A model of DNA ejection from bacteriophage

The molecular biomechanics of DNA ejection from bacteriophage is of interest to not only fundamental biological understandings but also practical applications such as the design of advanced site-specific and controllable drug delivery systems. In this paper, we analyze the viscous motion of a semiflexible polymer chain coming out of a strongly confined space as a model to investigate the effects of various structure confinements and frictional resistances encountered during the DNA ejection process. The theoretically predicted relations between the ejection speed, ejection time, ejection length, and other physical parameters, such as the phage type, total genome length and ionic state of external buffer solutions, show excellent agreement with in vitro experimental observations in the literature.

Bacteriophage Biocontrol Rescues Mice Bacteremic of Clinically Isolated Mastitis from Dairy Cows Associated with Methicillin-Resistant <i>Staphyloccocus aureus</i>

Methicillin-resistant Staphylococcus aureus (MRSA) is among the most alarming pathogens affecting both humans and the global bovine industry. The current control measures in hospitals and on farms for MRSA have proven to be inadequate leaving a need for new rapid control methods to curb MRSA infections in situ. New control measures for bacterial infection are widely sought, with particular interest in the applications for bacteriophages (phages) as a biocontrol or therapeutic agent. The current study uses a wild highly lytic phage isolated from cow’s milk taken from three farms in Baghdad, Iraq. The resulting phage was able to rescue 100% of the mice from a median lethal dose (LD50) or (1 × 108 CFU mL-1 per mouse) for MRSA wild isolates achieved when the phage: bacteria ratio was 100:1. Even when treatment was delayed for 6 h post lethal infection, to the point where all mice were moribund, 80% of them were rescued by a single injection of this phage preparation. Based on the current results, a comprehensive study is needed to guide further research on the MRSA phage as a biocontrol for MRSA mastitis in dairy cows to replace or reduce the use of antibiotics in animal husbandry.

Effect of Post-Treatment Conditions on the Inactivation of MS2 Bacteriophage as Indicator for Pathogenic Viruses after the Composting Process

A rural model composting toilet system still had some pathogens in the compost after months of operation and hence requires a post-treatment. The aim of the study was to sanitize compost withdrawn from the composting toilet by setting post-treatment conditions. The kinetics inactivation of MS2 bacteriophage, selected as indicator for pathogenic viruses were determined during post-treatment at different temperatures (30°C, 40°C and 50°C) with varying moisture contents (50%, 60% and 70%). As a result, the inactivation rates during the post-treatment were 0.093 - 0.020 h-1, 0.025 - 0.088 h1, 0.447 - 0.100 h-1 at 30°C, 40°C and 50°C respectively. The inactivation rate coefficient (k) values of MS2 bacteriophage depended on higher temperature but not on moisture content.

Survival and proliferation of the lysogenic bacteriophage CTXΦ in Vibrio cholerae

The lysogenic phage CTXΦ of Vibrio cholerae can transfer the cholera toxin gene both horizontally(inter-strain) and vertically(cell proliferation). Due to its diversity in form and species, the complexity of regulatory mechanisms, and the important role of the infection mechanism in the production of new virulent strains of V.cholerae, the study of the lysogenic phage CTXΦ has attracted much attention. Based on the progress of current research, the genomic features and their arrangement, the host-dependent regulatory mechanisms of CTXΦ phage survival, proliferation and propagation were reviewed to further understand the phage's role in the evolutionary and epidemiological mechanisms of V. cholerae.

Effect of bacteriophage lysin on lysogens

Objective:To study the effect of phage lysin on the growth of lysogens.Methods:Sputum specimens processed by modified Petroff's method were respectively treated with phagebiotics in combination with lysin and lysin alone.The specimens were incubated at 37 ℃ for 4 days.At the end of day 1,2,3 and day 4,the specimens were streaked on blood agar plates and incubated at37 ℃ for 18-24 hours.The growth of normal flora observed after day 1 was considered as lysogens.Results:Sputum specimens treated with phagebiotics-lysin showed the growth of lysogens.When specimens treated with lysin alone,lysogen formation was avoided and normal flora was controlled.Conclusions:Lysin may have no effect on the growth of lysogens.

Choice of Force Fields and Water Models for Sampling Solution Conformations of Bacteriophage T4 Lysozyme

A protein may exist as an ensem-ble of di erent conformations in solution,which cannot be repre-sented by a single static structure.Molecular dy-namics(MD)simulation has become a useful tool for sampling protein conformations in solution,but force elds and water models are important issues.This work presents a case study of the bacteriophage T4 lysozyme(T4L).We have found that MD simulations using a classic AMBER99SB force eld and TIP4P water model cannot well describe hinge-bending domain motion of the wild-type T4L at the timescale of one microsecond.Other combinations,such as a residue-speci c force eld called RSFF2+and a dispersion-corrected water model TIP4P-D,are able to sample reasonable solution conformations of T4L,which are in good agreement with experimental data.This primary study may provide candidates of force elds and water models for further investigating conformational transition of T4L.

The bacteriophage mu lysis system–A new mechanism of host lysis?

Bacteriophages are viruses that infect bacteria and can choose any one of the two alternative pathways for infection,i.e.,lysis or lysogeny.Phage lysis is one of the conventional biological processes required to spread infection from one bacterium to another.Our analysis suggests that in the paradigm bacteriophage Mu,six proteins might be involved in host cell lysis.Mu has a broad host range,and Mu-like phages were found in both Gram-negative and Gram-positive bacteria.An analysis of the genomes of Mu and Mu-like phages could be useful in elucidating the lysis mechanism in this group of phages.A detailed review of the various mechanisms of phage lysis and different proteins associated with the process will help researchers understand the phage biology and their life cycle in different bacteria.The recent increase in the number of multidrug-resistant(MDR)strains of bacteria and the usual long-term nature of new drug development has encouraged scientists to look for alternative strategies like phage therapy and the discovery of new lysis mechanisms.Understanding the lysis mechanism in the Mu-like phages could be exploited to develop alternative therapeutics to kill drug-resistant pathogenic bacteria.In this review article,we have analyzed the phage Mu-mediated host lysis system,which is unknown till now,and our analysis indicates a possibility of the existence of a new lysis mechanism operating in Mu.

Isolation and Characterization of Bacteriophages from Laban Jameed

Laban jameed is a dried salty dairy product obtained by fermentation of milk using a complex population of lactic acid bacteria. Jameed is considered a traditional food product in most eastern Mediterranean countries and is usually made from sheep or cow milk. The aim of this study was to assess phage contamination of jameed dairy product. Two phages were isolated: one from sheep milk jameed (PPUDV) and the other from cow milk jameed (PPURV). Each of the two bacteriophages was partially characterized. The PPUDV phage was identified as a single stranded DNA virus with an approximately 20 kb genome that was resistant to RNase, whereas PPURV phage possessed a double stranded RNA genome of approximately 20 kb and was resistant to DNase. The phage bacterial strain hosts were identified as Lactobacillus helveticus and Bacillus amyloliquefaciens for PPUDV and PPURV, respectively. One step growth curve using a double layer plaque assay test was carried out to monitor the phage life cycle after host infection. PPUDV showed a latent period of about 36 h, burst period of 70 h and a burst size of about 600 Plaque Forming Units (PFU) per infected cell. PPURV phage showed a latent period of about 24 h, burst period of 47 h and a burst size of about 700 PFU per infected cell. SDS-PAGE analysis of total viral proteins showed at least three major bands (27, 40, and 45 kDa) for PPUDV. This is the first study to report the isolation of both DNA and RNA bacteriophages from laban jameed. This study adds new insights into the complexity of dairy contamination and fermentation microbiology of the jameed revealing the existence of two viral genomes in this highly dried and salty dairy product.

Identification of a Morphogenic Intermediate of the Bacteriophage Mu Baseplate

Bacteriophage morphogenesis is a model system for investigating sequential molecular assembly. The Mu phage is one of the most classical Myoviridae. Although it is well known as a mobile genetic element, the details of its morphogenesis remain unclear. Analysis of conditional lethal mutants and genome analysis of the Mu phage have suggested that genes 42, 43, 44, 45, 46, 47, and 48 are essential for its baseplate assembly. Since we have already reported X-ray structures of the products of genes 44 (gp44) and 45 (gp45), we here tried to purify the remaining Mu phage baseplate subunits, gp42, gp43, gp46, gp47, and gp48, to investigate the baseplate assembly process. In the case of gp42 expression, the transformed E. coli cells showed growth inhibition after induction and no gp42 fractions were observed. However, gp43, gp46, gp47, and gp48 were successfully expressed and purified, although gp48 could not be applied to further analysis, because the amount of soluble fraction was very low. Based on analytical ultracentrifugation, we concluded that gp43 formed a monomer, gp46 was a monomer, and gp47 occurred as both a monomer and dimer in solution. Moreover, we found that gp43 and gp45 formed an intermediate complex in the baseplate assembly process.

Computational Modelling of Cholera Bacteriophage with Treatment

This paper examines the computational modelling of cholera bacteriophage with treatment. A nonlinear mathematical model for cholera bacteriophage and treatment is formulated and analysed. The effective reproduction number of the nonlinear model system is calculated by next generation operator method. By using the next generation matrix approach, the disease-free equilibrium is found to be locally stable at threshold parameter less than unity and unstable at threshold parameter greater than unity. Globally, the disease free equilibrium point is not stable due to existence of forward bifurcation at threshold parameter equal to unity. Stability analysis and numerical simulations suggest that the combination of bacteriophage and treatment may contribute to lessening the severity of cholera epidemics by reducing the number of Vibrio cholerae in the environment. Hence with the presence of bacteriophage virus and treatment, cholera is self-limiting in nature.

Therapeutic Potential of Staphylococcal Bacteriophages for Nasal Decolonization of <i>Staphylococcus aureus</i>in Mice

Bacteriophages represent a rich and unique resource of anti-infectives to counter the global problem of antibiotic resis- tance. In this work, we assessed the bactericidal activity of two virulent staphylococcal phages, K and 44AHJD, against S. aureus isolates of clinical significance, and tested their efficacy in vivo. The phage cocktail lysed >85% of the clinical isolates tested. Both the phages were purified by ion-exchange column chromatography following propagation in bioreactors. The purity profiles of the ion-exchange purified phages were compared with those of phages purified using cesium chloride density gradient ultracentrifugation, and infectiousness of the purified phages was confirmed by plaque forming assay. The in vivo efficacy of a phage cocktail was evaluated in an experimental murine nasal colonization model, which showed that the phage cocktail was efficacious. To our knowledge, this is the first report of phage use in an in vivo model of nasal carriage.

Importance of Bacteriophage in Combating Hospital-Acquired Infection (HAI)

Bacteriophages have a potentially important role to play in reducing the global incidence of Hospital Acquired Infection (HAI). Their use should be focused on reducing the use and over-use of antibiotics as part of integrated control measures in conjunction with various vaccination, sanitation procedures and prophylactic and treatment regimens. Bacteriophages offer exquisite specificity and efficacy in killing target bacterial strains, a phenomenon known for almost 100 years. However, their efficacy with respect to broad-spectrum antibiotics is poor due to the highly strain-selective nature of their killing and their rapid elimination from the body. Bacteriophage killing is a naturally-occurring process capable of limiting and eliminating bacterial populations in humans. This is achieved through exponential amplification of their number, if and when, they encounter a target bacterium. Unfortunately, processes employed for their commercial production today do not meet the same rigour as dictated for pharmaceutical products. Batch-to-batch reproducibility and molecular definition of target and phage strains must be demanded before their clinical use can become widespread. Elsewhere, historical data have demonstrated safety in humans beyond any doubt. Because patients continue to die in our healthcare centers internationally, the use of bacteriophage to help fight HAI should be reassessed. Here, relevant literature is reviewed.