Isolation and characterization of a virulent bacteriophage SPW specific for Staphylococcus aureus isolated from bovine mastitis of lactating dairy cattle

Phage-antibiotic synergism against Salmonella typhi isolated from stool samples of typhoid patients

BACKGROUND

Typhoid fever is a fatal disease in humans that is caused by Salmonella typhi. S. typhi infections need immediate antibiotic therapy, and their extensive use has led to multidrug-resistant (MDR) pathogens. The use of bacteriophages is becoming a new way to treat these resistant bacteria. This research was directed to bacteriophage isolation against S. typhi and to determine phage-antibiotic synergism.

AIMS

To isolate bacteriophages targeting S. typhi, the causative agent of typhoid fever, and investigate their potential synergistic effects when combined with antibiotics.

STUDY DESIGN

A cross-sectional study.

METHODS

The Widal test was positive; twenty diarrheal stool samples were taken, and for confirmation of S. typhi, different biochemical tests were performed. The disc-diffusion technique was used to determine antimicrobial resistance, and the double agar overlay method was used for bacteriophage isolation from sewage water against S. typhi. To test antibiotic-phage synergism, the S. typhi bacteria was treated by phages together with varying antibiotic concentrations.

RESULTS

Eleven samples were positive for S. typhi with black colonies on SS-agar. These were catalase and MR positive with alkali butt on TSI. Clear plaques were observed after the agar overlay. Isolated phages were stable at various pH and temperature levels. Synergism was observed on agar plate. The zone was enlarged when phages were combined with bacterial lawn culture and ciprofloxacin disk. Bacterial growth inhibition had a significant p-value of 0.03 in titration plates, with the phage-ciprofloxacin combination being more effective than the phage and antibiotic alone.

CONCLUSION

The study highlights the synergistic effects of isolated bacteriophages with antibiotics, which are not only effective against S. typhi infection but also decrease antibiotic resistance.

Isolation and genomic characterization of Staphylococcus aureus bacteriophages from Chennai, India

We isolated and characterized two lytic bacteriophages against Staphylococcus aureus named TANUVAS_MVC-VPHSA1 and TANUVAS_MVC-VPHSA2, with the aim of investigating their genomic and structural features. The bacteriophages belong to the Caudoviricetes, and their genomes have sizes of 50,505 and 50,516 base pairs with a GC content of 41.4%.

Isolation and encapsulation of bacteriophage with chitosan nanoparticles for biocontrol of multidrug-resistant methicillin-resistant Staphylococcus aureus isolated from broiler poultry farms

This study was divided into two parts. The first part, the determination of methicillin-resistant Staphylococcus aureus (MRSA) prevalence in 25 broiler chicken farms, with the detection of multidrug resistant MRSA strains. The prevalence of MRSA was 31.8% (159 out of 500 samples) at the level of birds and it was 27% (27 out of 100) in the environmental samples. The highest antimicrobial resistance of the recovered MRSA strains was recorded to streptomycin (96%). All isolates (100%) had multidrug resistance (MDR) to four or more antibiotics with 16 distinct antibiotic resistant patterns, and multiple antibiotic resistance index (MARI) of 0.4-1. The second part, implementing novel biocontrol method for the isolated multidrug resistant MRSA strains through the isolation of its specific phage and detection of its survival rate at different pH and temperature degrees and lytic activity with and without encapsulation by chitosan nanoparticles (CS-NPs). Encapsulated and non-encapsulated MRSA phages were characterized using transmission electron microscope (TEM). Encapsulation of MRSA phage with CS-NPs increasing its lytic activity and its resistance to adverse conditions from pH and temperature. The findings of this study suggested that CS-NPs act as a protective barrier for MRSA phage for the control of multidrug resistant MRSA in broiler chicken farms.

Surface-enhanced Raman spectroscopy for the characterization of bacterial pellets of Staphylococcus aureus infected by bacteriophage

Drug-resistant pathogenic bacteria are a major cause of infectious diseases in the world and they have become a major threat through the reduced efficacy of developed antibiotics. This issue can be addressed by using bacteriophages, which can kill lethal bacteria and prevent them from causing infections. Surface-enhanced Raman spectroscopy (SERS) is a promising technique for studying the degradation of infectious bacteria by the interaction of bacteriophages to break the vicious cycle of drug-resistant bacteria and help to develop chemotherapy-independent remedial strategies. The phage (viruses)-sensitive Staphylococcus aureus (S. aureus) bacteria are exposed to bacteriophages (Siphoviridae family) in the time frame from 0 min (control) to 50 minutes with intervals of 5 minutes and characterized by SERS using silver nanoparticles as SERS substrate. This allows us to explore the effects of the bacteriophages against lethal bacteria (S. aureus) at different time intervals. The differentiating SERS bands are observed at 575 (C-C skeletal mode), 620 (phenylalanine), 649 (tyrosine, guanine (ring breathing)), 657 (guanine (COO deformation)), 728-735 (adenine, glycosidic ring mode), 796 (tyrosine (C-N stretching)), 957 (C-N stretching (amide lipopolysaccharides)), 1096 (PO2 (nucleic acid)), 1113 (phenylalanine), 1249 (CH2 of amide III, N-H bending and C-O stretching (amide III)), 1273 (CH2, N-H, C-N, amide III), 1331 (C-N stretching mode of adenine), 1373 (in nucleic acids (ring breathing modes of the DNA/RNA bases)) and 1454 cm-1 (CH2 deformation of saturated lipids), indicating the degradation of bacteria and replication of bacteriophages. Multivariate data analysis was performed by employing principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) to study the biochemical differences in the S. aureus bacteria infected by the bacteriophage. The SERS spectral data sets were successfully differentiated by PLS-DA with 94.47% sensitivity, 98.61% specificity, 94.44% precision, 98.88% accuracy and 81.06% area under the curve (AUC), which shows that at 50 min interval S. aureus bacteria is degraded by the replicating bacteriophages.

Characterization of bacteriophage BUCT631 lytic for K1 Klebsiella pneumoniae and its therapeutic efficacy in Galleria mellonella larvae

Severe infections caused by multidrug-resistant Klebsiella pneumoniae (K. pneumoniae) highlight the need for new therapeutics with activity against this pathogen. Phage therapy is an alternative treatment approach for multidrug-resistant K. pneumoniae infections. Here, we report a novel bacteriophage (phage) BUCT631 that can specifically lyse capsule-type K1 K. pneumoniae. Physiological characterization revealed that phage BUCT631 could rapidly adsorb to the surface of K. pneumoniae and form an obvious halo ring, and it had relatively favorable thermal stability (4-50 ​°C) and pH tolerance (pH ​= ​4-12). In addition, the optimal multiplicity of infection (MOI) of phage BUCT631 was 0.01, and the burst size was approximately 303 ​PFU/cell. Genomic analysis showed that phage BUCT631 has double-stranded DNA (total length of 44,812 bp) with a G ​+ ​C content of 54.1%, and the genome contains 57 open reading frames (ORFs) and no virulence or antibiotic resistance related genes. Based on phylogenetic analysis, phage BUCT631 could be assigned to a new species in the genus Drulisvirus of the subfamily Slopekvirinae. In addition, phage BUCT631 could quickly inhibit the growth of K. pneumoniae within 2 ​h in vitro and significantly elevated the survival rate of K. pneumoniae infected Galleria mellonella larvae from 10% to 90% in vivo. These studies suggest that phage BUCT631 has promising potential for development as a safe alternative for control and treatment of multidrug-resistant K. pneumoniae infection.

Bacteriophage Therapy to Control Bovine Mastitis: A Review

Bovine mastitis is a polymicrobial disease characterised by inflammation of the udders of dairy and beef cattle. The infection has huge implications to health and welfare of animals, impacting milk and beef production and costing up to EUR 32 billion annually to the dairy industry, globally. Bacterial communities associated with the disease include representative species from Staphylococcus, Streptococcus, Enterococcus, Actinomyces, Aerococcus, Escherichia, Klebsiella and Proteus. Conventional treatment relies on antibiotics, but antimicrobial resistance, declining antibiotic innovations and biofilm production negatively impact therapeutic efficacy. Bacteriophages (phages) are viruses which effectively target and lyse bacteria with extreme specificity and can be a valuable supplement or replacement to antibiotics for bovine mastitis. In this review, we provide an overview of the etiology of bovine mastitis, the advantages of phage therapy over chemical antibiotics for the strains and research work conducted in the area in various model systems to support phage deployment in the dairy industry. We emphasise work on phage isolation procedures from samples obtained from mastitic and non-mastitic sources, characterisation and efficacy testing of single and multiple phages as standalone treatments or adjuncts to probiotics in various in vitro, ex vivo and in vivo bovine mastitis infection models. Furthermore, we highlight the areas where improvements can be made with focus on phage cocktail optimisation, formulation, and genetic engineering to improve delivery, stability, efficacy, and safety in cattle. Phage therapy is becoming more attractive in clinical medicine and agriculture and thus, could mitigate the impending catastrophe of antimicrobial resistance in the dairy sector.

Bacteriophages in Infectious Diseases and Beyond-A Narrative Review

The discovery of antibiotics has revolutionized medicine and has changed medical practice, enabling successful fighting of infection. However, quickly after the start of the antibiotic era, therapeutics for infectious diseases started having limitations due to the development of antimicrobial resistance. Since the antibiotic pipeline has largely slowed down, with few new compounds being produced in the last decades and with most of them belonging to already-existing classes, the discovery of new ways to treat pathogens that are resistant to antibiotics is becoming an urgent need. To that end, bacteriophages (phages), which are already used in some countries in agriculture, aquaculture, food safety, and wastewater plant treatments, could be also used in clinical practice against bacterial pathogens. Their discovery one century ago was followed by some clinical studies that showed optimistic results that were limited, however, by some notable obstacles. However, the rise of antibiotics during the next decades left phage research in an inactive status. In the last decades, new studies on phages have shown encouraging results in animals. Hence, further studies in humans are needed to confirm their potential for effective and safe treatment in cases where there are few or no other viable therapeutic options. This study reviews the biology and applications of phages for medical and non-medical uses in a narrative manner.

Statistical optimization of a podoviral anti-MRSA phage CCASU-L10 generated from an under sampled repository: Chicken rinse

Introduction

The insurgence of antimicrobial resistance is an imminent health danger globally. A wide range of challenging diseases are attributed to methicillin-resistant Staphylococcus aureus (MRSA) as it is weaponized with a unique array of virulence factors, and most importantly, the resistance it develops to most of the antibiotics used clinically. On that account, the present study targeted the optimization of the production of a bacteriophage active against MRSA, and evaluating some of its characters.

Methods and results

The bacteriophage originated from a quite peculiar environmental source, raw chicken rinse and was suggested to belong to Podoviridae, order Caudovirales. It withstood a variety of extreme conditions and yield optimization was accomplished via the D-optimal design by response surface methodology (RSM). A reduced quadratic model was generated, and the ideal production conditions recommended were pH 8, glycerol 0.9% v/v, peptone 0.08% w/v, and 107 CFU/ml as the host inoculum size. These conditions led to a two-log fold increase in the phage titer (1.17x10¹² PFU/ml), as compared to the regular conditions.

Discussion

To conclude, statistical optimization successfully enhanced the output of the podoviral phage titer by two-log fold and therefore, can be regarded as a potential scale-up strategy. The produced phage was able to tolerate extreme environmental condition making it suitable for topical pharmaceutical preparations. Further preclinical and clinical studies are required to ensure its suitability for use in human.

Alternatives to Antimicrobial Treatment in Bovine Mastitis Therapy: A Review

Despite preventive and therapeutic measures, mastitis continues to be the most prevalent health problem in dairy herds. Considering the risks associated with antibiotic therapy, such as compromised effectiveness due to the emergence of resistant bacteria, food safety issues, and environmental impact, an increasing number of scientific studies have referred to the new therapeutic procedures that could serve as alternatives to conventional therapy. Therefore, the aim of this review was to provide insight into the currently available literature data in the investigation of non-antibiotic alternative approaches. In general, a vast number of in vitro and in vivo available data offer the comprehension of novel, effective, and safe agents with the potential to reduce the current use of antibiotics and increase animal productivity and environmental protection. Constant progress in this field could overcome treatment difficulties associated with bovine mastitis and considerable global pressure being applied on reducing antimicrobial therapy in animals.

Effective Treatment of Staphylococcus aureus Intramammary Infection in a Murine Model Using the Bacteriophage Cocktail StaphLyse™

Staphylococcus aureus causes intramammary infections (IMIs), which are refractory to antibiotic treatment and frequently result in chronic mastitis. IMIs are the leading cause of conventional antibiotic use in dairy farms. Phage therapy represents an alternative to antibiotics to help better manage mastitis in cows, reducing the global spread of resistance. A mouse mastitis model of S. aureus IMI was used to study the efficacy of a new cocktail of five lytic S. aureus-specific phages (StaphLyse™), administered either via the intramammary (IMAM) route or intravenously (IV). The StaphLyse™ phage cocktail was stable in milk for up to one day at 37 °C and up to one week at 4 °C. The phage cocktail was bactericidal in vitro against S. aureus in a dose-dependent manner. A single IMAM injection of this cocktail given 8 h after infection reduced the bacterial load in the mammary glands of lactating mice infected with S. aureus, and as expected, a two-dose regimen was more effective. Prophylactic use (4 h pre-challenge) of the phage cocktail was also effective, reducing S. aureus levels by 4 log10 CFU per gram of mammary gland. These results suggest that phage therapy may be a viable alternative to traditional antibiotics for the control of S. aureus IMIs.

Distribution of mcr-1 Harboring Hypervirulent Klebsiella pneumoniae in Clinical Specimens and Lytic Activity of Bacteriophage KpnM Against Isolates

Background

The World Health Organization (WHO) has declared the multi-drug resistant (MDR) Klebsiella pneumoniae as one of the critical bacterial pathogens. The dearth of new antibiotics and inadequate therapeutic options necessitate finding alternative options. Bacteriophages are known as enemies of bacteria and are well-recognized to fight MDR pathogens.

Methods

A total of 150 samples were collected from different clinical specimens through a convenient sampling technique. Isolation, identification, and antibiotic susceptibility testing (AST) of K. pneumoniae were done by standard and validated microbiological procedures. Molecular identification of virulence factors and antibiotic resistance genes (ARGs) was carried out through polymerase chain reaction (PCR) by using specific primers. For bacteriophage isolation, hospital sewage samples were processed for phage enrichment, purification, and further characterization ie, transmission electron microscopy (TEM) and stability testing, etc. followed by evaluation of the lytic potential of the phage.

Results

Overall, a total of 41% of isolates of K. pneumoniae were observed as hypervirulent K. pneumoniae (hvKp). Among hvKp, a total of 12 (42%) were detected as MDR hvKp. A total of 37% of all MDR isolates were found resistant to colistin, and 66% of the colistin resistance isolates were recorded as mcr-1 positive. Isolated phage KpnM had shown lytic activity against 53 (79%) K. pneumoniae isolates. Remarkably, all 8 mcr-1 harboring MDR hvKp and non-hvKp isolates were susceptible to KpnM phage.

Conclusion

Significant distribution of mcr-1 harboring hypervirulent Klebsiella pneumoniae was observed in clinical specimens, which is worrisome for the health system of the country. Characterized phage KpnM exhibited encouraging results and showed the lytic activity against the mcr-1 harboring hvKp isolates, which may be used as a prospective alternative control strategy to fight this ominous bacterium.

TSP, a virulent Podovirus, can control the growth of Staphylococcus aureus for 12 h

Methicillin-resistant Staphylococcus aureus (MRSA) is a prevailing nosocomial pathogen that is increasingly isolated in community settings. It shows resistance against all beta-lactam drugs and has acquired mechanisms to resist other groups of antibiotics. To tackle this emerging issue of MRSA, there is an urgent need for antibiotic alternatives, and utilizing lytic bacteriophages is one of the most promising therapeutic approaches. In the present study, a lytic bacteriophage TSP was isolated from hospital wastewater against MRSA. The phage efficiently inhibited bacterial growth for up to 12 h at MOI of 1 and 10. TSP phage showed activity against various isolates of MRSA and MSSA, isolated from different clinical samples, with variable antibiotic susceptibility patterns. The bacteriophage TSP showed stability at varying temperatures (25 °C, 37 °C) and pH values (5–9), while its maximum storage stability was observed at 4 °C. It had a short latent period (20 min) and burst size of 103 ± 5pfu/infected cells. TSP genome sequence and restriction analysis revealed that its genome has a linear confirmation and length of 17,987 bp with an average GC content of 29.7%. According to comparative genomic analysis and phylogenetic tree,TSP phage can be considered a member of genus “P68viruses”. The strong lytic activity and short latent period in addition to its lytic nature makes it a good candidate for phage therapy against MRSA infections, if it proves to be effective in in-vivo studies.

An Anti-MRSA Phage From Raw Fish Rinse: Stability Evaluation and Production Optimization

Accumulating evidence has denoted the danger of resistance in tenacious organisms like methicillin-resistant Staphylococcus aureus (MRSA). MRSA, a supple bacterium that adopts a variety of antibiotic resistance mechanisms, is the cause of multiple life-threatening conditions. Approaching a post-antibiotic era, bacteria-specific natural predators, bacteriophages, are now given the chance to prove eligible for joining the antibacterial weaponry. Considering the foregoing, this study aimed at isolating bacteriophages with promising anti-MRSA lytic activity, followed by characterization and optimization of the production of the bacteriophage with the broadest host range. Five phages were isolated from different environmental sources including the rinse of raw chicken egg, raw milk, and, remarkably, the raw meat rinses of chicken and fish. Examined for lytic activity against a set of 23 MRSA isolates collected from various clinical specimens, all five phages showed relatively broad host ranges with the bacteriophage originally isolated from raw fish rinse showing lytic activity against all the isolates tested. This phage is suggested to be a member of Siphoviridae family, order Caudovirales, as revealed by electron microscopy. It also exhibited good thermal stability and viability at different pH grades. Moreover, it showed reasonable stability against UV light and all viricidal organic solvents tested. Optimization using D-optimal design by response surface methodology was carried out to enhance the phage yield. The optimum conditions suggested by the generated model were a pH value of 7, a carbon source of 0.5% w/v sucrose, and a nitrogen source of 0.1% w/v peptone, at a temperature of 28°C and a bacterial inoculum size of 107 CFU/ml, resulting in a 2 log-fold increase in the produced bacteriophage titer. Overall, the above findings indicate the lytic ability inflicted by this virus on MRSA. Apparently, its stability under some of the extreme conditions tested implies its potential to be a candidate for pharmaceutical formulation as an anti-MRSA therapeutic tool. We hope that bacteriophages could tip the balance in favor of the human front in their battle against multidrug-resistant pathogens.

Characterization and Genomic Analysis of a Novel Drexlervirial Bacteriophage IME268 with Lytic Activity Against Klebsiella pneumoniae

Introduction

Klebsiella pneumoniae, a multidrug resistant bacterium, that causes nosocomial infections including septicemia, pneumonia etc. Bacteriophages are potential antimicrobial agents for the treatment of antibiotic resistant bacteria.

Methods and Results

In this study, a novel bacteriophage IME268 was isolated from hospital sewage against clinical multi-drug resistant Klebsiella pneumoniae. Transmission electron microscopy and genomic characterization of this phage exhibited it belongs to the Webervirus genus, Drexlerviridae family. Phage IME268 possessed a double-stranded DNA genome composed of 49,552bp with a GC content of 50.5%. The phage genome encodes 77 open reading frames, out of 44 are hypothetical proteins while 33 had assigned putative functions. No tRNA, virulence related or antibiotic resistance genes were found in phage genome. Comparative genomic analysis showed that phage IME268 has 95% identity with 87% query cover with other phages in NCBI database. Multiplicity of infection, one step growth curve and host range of phage were also measured.

Conclusion

According to findings, Phage IME268 is a promising biological agent that infects Klebsiella pneumoniae and can be used in future phage therapies.

Isolation and Characterization of Bacteriophage Against Wastewater Isolates of Methicillin-resistant Staphylococcus aureus

Background: Methicillin-resistant Staphylococcus aureus (MRSA) not only is a notorious pathogen in clinical settings but also is an environmental issue that its presence in environmental wastewater is highlighted by several reports. Due to the negative impacts of antibiotics, alternatives like bacteriophages, as biocontrol, are considered safe. However, not all bacteriophages are safe. Thus, the characterization of bacteriophages is necessary. Objectives: This study aimed to, firstly isolate MRSA from wastewater and, secondly to perform bacteriophage isolation from the water samples to investigate its physical and genomic characteristics. Methods: Water samples were collected from seven locations across Nagpur city, India, bacteria were isolated on the S. aureus specific agar. For detecting MRSA, we followed the disc diffusion method. Isolation of bacteriophage against MRSA was performed by a modified enrichment method. We investigated its physical characteristics by the one-step growth rate, adsorption rate, host range, survivability, electron microscopy, and genomic sequencing for bioinformatics analysis. Results: Four MRSA were isolated from wastewater samples. We got a bacteriophage against an MRSA from the river Ganga. The bacteriophage belongs to the Podoviridae family, subfamily Autographivirinae. It was stable till 40°C and could survive at a highly alkaline pH. It is specific to its host. The bacteriophage DNA encodes 52 ORF, and all predicted genes are on the same strand; it also encodes a phage RNA polymerase. Conclusions: It is the first report of an S. aureus bacteriophage that belongs to the sub-family Autographivirinae. Our study and literature survey conclude that S. aureus bacteriophages of the Podoviridae family are safe for various downstream applications.

Lytic Bacteriophages Against Bacterial Biofilms Formed by Multidrug-Resistant Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus Isolated from Burn Wounds

Background: Use of bacteriophages as antibiofilm agents to tackle multidrug-resistant bacteria has gained importance in recent years. Materials and Methods: In this study, biofilm formation by Staphylococcus aureus, Pseudomona aeruginosa, Klebsiella pneumoniae, and Escherichia coli under different growth conditions was studied. Furthermore, the ability of bacteriophages to inhibit biofilm formation was analyzed. Results: Under dynamic growth condition, wherein the medium is renewed for every 12 h, the amount of biomass produced and log₁₀ colony-forming unit counts of all bacterial species studied was highest when compared with other growth conditions tested. Biomass of biofilms produced was drastically reduced when incubated for 2 or 4 h with bacteriophages vB_SAnS_SADP1, vB_PAnP_PADP4, vB_KPnM_KPDP1, and vB_ECnM_ECDP3. Scanning electron microscopy and confocal laser scanning microscopy analyses indicated that the reduction in biomass was due to the lytic action of the bacteriophages. Conclusions: Results of our study reinforce the concept of developing bacteriophages as alternatives to antibiotics to treat bacterial infections.

Biochemical and genomic characterization of a novel bacteriophage BUCT555 lysing Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is a common conditional pathogen, and it is naturally resistant to most commonly used clinical antibiotics. The bacteriophage is considered to be a potential antibiotic alternative for treating multi-drug-resistant bacteria. In this study, a bacteriophage BUCT555 was isolated from hospital sewage for lysing the clinical multi-drug resistant Stenotrophomonas maltophilia. Electron microscopy studies revealed this phage belongs to the Podoviridae family. The double-stranded DNA genome of bacteriophage BUCT555 is composed of 39,440 bp with a GC content of 61.43%. The genome contains 57 open reading frames, 14 of which had assigned functions, while no virulence related genes, antibiotic resistance genes or tRNA were identified. The burst size of BUCT555 was 204 pfu per infected cell. Structure proteins of bacteriophage BUCT555 generated by SDS-PAGE and HPLC-MS revealed that it contains seven proteins with molecular weight ranging from 19 to 89 kDa. BLASTn analysis showed that phage BUCT555 has 2% homology with other phages in NCBI database, suggesting BUCT555 is a new phage genus of Podoviridae that infects Stenotrophomonas maltophilia. Characterization of the bacteriophage BUCT555 enriches our knowledge about the diversity of Stenotrophomonas maltophilia bacteriophages.

The human milk microbiome: who, what, when, where, why, and how?

Human milk (HM) contains an incredible array of microorganisms. These likely contribute to the seeding of the infant gastrointestinal microbiome, thereby influencing infant immune and metabolic development and later-life health. Given the importance of the HM microbiota in this context, there has been an increase in research efforts to characterize this in different populations and in relation to different maternal and infant characteristics. However, despite a decade of intensive research, there remain several unanswered questions in this field. In this review, the "5 W+H" approach (who, what, when, where, why, and how) is used to comprehensively describe the composition, function, and origin of the HM microbiome. Here, existing evidence will be drawn together and critically appraised to highlight avenues for further research, both basic and applied. Perhaps the most interesting of these is the potential to modulate the HM microbiome using pre/probiotics or dietary interventions. Another exciting possibility is the personalization of donor milk for women with insufficient supply. By gaining a deeper understanding of the HM microbiome, opportunities to intervene to optimize infant and lifelong health may be identified.

Phage Therapy in Veterinary Medicine

To overcome the obstacle of antimicrobial resistance, researchers are investigating the use of phage therapy as an alternative and/or supplementation to antibiotics to treat and prevent infections both in humans and in animals. In the first part of this review, we describe the unique biological characteristics of bacteriophages and the crucial aspects influencing the success of phage therapy. However, despite their efficacy and safety, there is still no specific legislation that regulates their use. In the second part of this review, we describe the comprehensive research done in the past and recent years to address the use of phage therapy for the treatment and prevention of bacterial disease affecting domestic animals as an alternative to antibiotic treatments. While in farm animals, phage therapy efficacy perspectives have been widely studied in vitro and in vivo, especially for zoonoses and diseases linked to economic losses (such as mastitis), in pets, studies are still few and rather recent.

Patterns of virus growth across the diversity of life

Although viruses in their natural habitats add up to less than 10% of the biomass, they contribute more than 90% of the genome sequences [1]. These viral sequences or 'viromes' encode viruses that populate the Earth's oceans [2, 3] and terrestrial environments [4, 5], where their infections impact life across diverse ecological niches and scales [6, 7], including humans [8-10]. Most viruses have yet to be isolated and cultured [11-13], and surprisingly few efforts have explored what analysis of available data might reveal about their nature. Here, we compiled and analyzed seven decades of one-step growth and other data for viruses from six major families, including their infections of archaeal, bacterial and eukaryotic hosts [14-191]. We found that the use of host cell biomass for virus production was highest for archaea at 10%, followed by bacteria at 1% and eukarya at 0.01%, highlighting the degree to which viruses of archaea and bacteria exploit their host cells. For individual host cells, the yield of virus progeny spanned a relatively narrow range (10-1000 infectious particles per cell) compared with the million-fold difference in size between the smallest and largest cells. Furthermore, healthy and infected host cells were remarkably similar in the time they needed to multiply themselves or their virus progeny. Specifically, the doubling time of healthy cells and the delay time for virus release from infected cells were not only correlated (r = 0.71, p < 10-10, n = 101); they also spanned the same range from tens of minutes to about a week. These results have implications for better understanding the growth, spread and persistence of viruses in complex natural habitats that abound with diverse hosts, including humans and their associated microbes.

Enhancing Drug Efficacy against Mastitis Pathogens-An In Vitro Pilot Study in Staphylococcus aureus and Staphylococcus epidermidis

BACKGROUND

Bovine mastitis is one of the major infectious diseases in dairy cattle, resulting in large economic loss due to decreased milk production and increased production cost to the dairy industry. Antibiotics are commonly used to prevent/treat bovine mastitis infections. However, increased antibiotic resistance and consumers' concern regarding antibiotic overuse make it prudent and urgent to develop novel therapeutic protocols for this disease.

MATERIALS AND METHODS

Potential druggable targets were found in 20 mastitis-causing pathogens and conserved and unique targets were identified. Bacterial strains Staphylococcus aureus (ATCC 29213, and two clinical isolates CI 1 and CI 2) and Staphylococcus epidermidis (ATCC 12228, and two clinical isolates CI 1 and CI 2) were used in the present study for validation of an effective drug combination.

RESULTS

In the current study, we identified the common and the unique druggable targets for twenty mastitis-causing pathogens using an integrative approach. Furthermore, we showed that phosphorylcholine, a drug for a unique target gamma-hemolysin component B in Staphylococcus aureus, and ceftiofur, the mostly used veterinary antibiotic that is FDA approved for treating mastitis infections, exhibit a synergistic effect against S. aureus and a strong additive effect against Staphylococcus epidermidis in vitro.

CONCLUSION

Based on the data generated in this study, we propose that combination therapy with drugs that work synergistically against conserved and unique targets can help increase efficacy and lower the usage of antibiotics for treating bacterial infections. However, these data need further validations in animal models of infection.

Characterization of lytic activity of Phage SAvB14 on Staphylococcus aureus variant bovis

Objective

The objective of this study was to investigate the intensity of phage infection caused by Phage SAvB14, which was isolated from dairy farms, depending on the initial number of Staphylococcus aureus cells in the medium.

Material and methods

To evaluate the impact of the viable bacteria S. aureus var. bovis on the intensity of phage infection caused by Phage SAvB14, 1 mg of phagolysate (phage titer 10⁵ CFU/ ml) was introduced in 9 ml of nutrient broth with an appropriate amount of daily culture of S. aureus var. bovis under study. The number of viable staphylococci was determined by total viable count/ml.

Results

In this experiment, we found that the intensity of phages lytic activity was dependent on the number of sensitive bacterial cells in the volume of the culture medium. Effective phage therapy requires a high concentration of phages in the medium (inflammation foci) for rapid contact of the virus with bacteria.

Conclusion

When developing a phage drug to treat subclinical mastitis, it is necessary to increase the phage titer in the drug or its dosage compared to the clinical form, as there is a lower probability of phage contact with a susceptible microbial cell. Besides, at a high concentration of bacteria, there is a gradual decrease in nutrients in the medium, resulting in phages going back to the condition of lysogeny.

Community-acquired pneumonia: aetiology, antibiotic resistance and prospects of phage therapy

Bacteria are the most common aetiological agents of community-acquired pneumonia (CAP) and use a variety of mechanisms to evade the host immune system. With the emerging antibiotic resistance, CAP-causing bacteria have now become resistant to most antibiotics. Consequently, significant morbimortality is attributed to CAP despite their varying rates depending on the clinical setting in which the patients being treated. Therefore, there is a pressing need for a safe and effective alternative or supplement to conventional antibiotics. Bacteriophages could be a ray of hope as they are specific in killing their host bacteria. Several bacteriophages had been identified that can efficiently parasitize bacteria related to CAP infection and have shown a promising protective effect. Thus, bacteriophages have shown immense possibilities against CAP inflicted by multidrug-resistant bacteria. This review provides an overview of common antibiotic-resistant CAP bacteria with a comprehensive summarization of the promising bacteriophage candidates for prospective phage therapy.

Staphylococcus aureus persistence properties associated with bovine mastitis and alternative therapeutic modalities

Staphylococcus aureus is an important agent of contagious bovine intramammary infections in dairy cattle. Its ability to persist inside the udder is based on the presence of important mechanisms such as its ability to form biofilms, polysaccharide capsules small colony variants, and their ability to invade professional and nonprofessional cells, which will protect S. aureus from the innate and adaptive immune response of the cow, and from antibiotics that are no longer considered to be sufficient against S. aureus bovine mastitis. In this review, we present the recent research outlining S. aureus persistence properties inside the mammary gland, including its regulation mechanisms, and we highlight alternative therapeutic strategies that were tested against S. aureus isolated from bovine mastitis such as the use of probiotic bacteria, bacteriocins and bacteriophages. Overall, the persistence of S. aureus inside the mammary gland remains a pressing veterinary problem. A thorough understanding of staphylococcal persistence mechanisms will elucidate novel ways that can help in the identification of novel treatments.

Bacteriophages and associated endolysins in therapy and prevention of mastitis and metritis in cows: Current knowledge

Bacteriophages and the associated endolysins have been proposed as an alternative to antibiotic treatment of mastitis and metritis in cows. Many bacteriophages have been isolated and characterized with a large amount of lytic potential against the bacteria causing mastitis and metritis in cows. Several endolysins with marked lytic activity against mastitis pathogens in vitro were also produced from staphylococcal and streptococcal bacteriophages. In the few clinical studies, however, there has been marginal efficacy of bacteriophages in the therapy of mastitis caused by Staphylococcus aureus. Similarly, lytic bacteriophages have marked antimicrobial activity in vitro against E. coli strains from the uteri of postpartum dairy cows. In clinical studies, however, neither administration of bacteriophages early postpartum nor prepartum was effective in the prevention of metritis in cows. More clinical studies on the effectiveness of bacteriophages and the associated endolysins in the prevention and therapy of mastitis and metritis in cows, therefore, are needed.

Isolation, Characterization and Genomic Analysis of a Novel Bacteriophage VB_EcoS-Golestan Infecting Multidrug-Resistant Escherichia coli Isolated from Urinary Tract Infection

Escherichia coli (E. coli) is one of the most common uropathogenic bacteria. The emergence of multi-drug resistance among these bacteria resulted in a worldwide public health problem which requires alternative treatment approaches such as phage therapy. In this study, phage VB_EcoS-Golestan, a member of Siphoviridae family, with high lytic ability against E. coli isolates, was isolated from wastewater. Its burst size was large and about 100 plaque-forming units/infected cell, rapid adsorption time, and high resistance to a broad range of pH and temperatures. Bioinformatics analysis of the genomic sequence suggests that VB_EcoS-Golestan is a new phage closely related to Escherichia phages in the Kagunavirus genus, Guernseyvirinae subfamily of Siphoviridae. The genome size was 44829 bp bp that encodes 78 putative ORFs, no tRNAs, 7 potential promoter sequences and 13 Rho-factor-independent terminators. No lysogenic mediated genes were detected in VB_EcoS-Golestan genome. Overall VB_EcoS-Golestan might be used as a potential treatment approach for controlling E. coli mediated urinary tract infection, however, further studies are essential to ensure its safety.

Isolation and application of bacteriophages alone or in combination with nisin against planktonic and biofilm cells of Staphylococcus aureus

Staphylococcus aureus is a notorious foodborne pathogen since it has ability to produce variety of toxins including heat-stable enterotoxin, form biofilm, and acquire resistance to antibiotics. Biocontrol of foodborne pathogens by lytic bacteriophages garners increasing interest from both researchers and food industry. In the present study, 29 phages against S. aureus were successfully isolated from chicken, pork, and fish. Characterization of the isolates revealed that phage SA46-CTH2 belonging to Podoviridae family had a number of features suitable for food industry applications such as wide host range, short latent period, large burst size, high stress tolerance, and a genome free of virulence genes. Furthermore, phage SA46-CTH2 alone or in combination with nisin exhibited great efficacy in reducing planktonic and biofilm cells of S. aureus at various conditions tested. The combination of phage SA46-CTH2 and nisin was also found to be able to inhibit the regrowth of S. aureus at both 37 and 24 °C.Key points• A total of 29 S. aureus phages were successfully isolated from fish, pork, and chicken products. • Phage SA46-CTH2 was characterized by host range, morphology, and genome sequencing. • SA46-CTH2 significantly reduced both planktonic and biofilm cells of S. aureus. • Combination of SA46-CTH2 and nisin inhibited the regrowth of S. aureus.

The Novel Enterococcus Phage vB_EfaS_HEf13 Has Broad Lytic Activity Against Clinical Isolates of Enterococcus faecalis

Enterococcus faecalis is a Gram-positive, facultative anaerobic bacterium frequently found in the gastrointestinal tract, oral cavity, and periodontal tissue. Although it is considered a commensal, it can cause bacteremia, endocarditis, endodontic infections, and urinary tract infections. Because antibiotics are cytotoxic not only to pathogens, but also to health-beneficial commensals, phage therapy has emerged as an alternative strategy to specifically control pathogenic bacteria with minimal damage to the normal flora. In this study, we isolated a novel phage, Enterococcus phage vB_EfaS_HEf13 (phage HEf13), with broad lytic activity against 12 strains of E. faecalis among the three laboratory strains and 14 clinical isolates of E. faecalis evaluated. Transmission electron microscopy showed that phage HEf13 has morphological characteristics of the family Siphoviridae. Phage HEf13 was stable at a wide range of temperature (4–60°C) and showed tolerance to acid or alkaline (pH 3–12) growth conditions. Phage HEf13 had a short latent period (25 min) with a large burst size (approximately 352 virions per infected cell). The lytic activity of phage HEf13 at various multiplicities of infection consistently inhibited the growth of diverse clinical isolates of E. faecalis without any lysogenic process. Moreover, phage HEf13 showed an effective lytic activity against E. faecalis on human dentin ex vivo infection model. Whole genome analysis demonstrated that the phage HEf13 genome contains 57,811 bp of double-stranded DNA with a GC content of 40.1% and 95 predicted open reading frames (ORFs). Annotated functional ORFs were mainly classified into four groups: DNA replication/packaging/regulation, phage structure, host cell lysis, and additional functions such as RNA transcription. Comparative genomic analysis demonstrated that phage HEf13 is a novel phage that belongs to the Sap6virus lineage. Furthermore, the results of multiple sequence alignment showed that polymorphism of phage infection protein of E. faecalis (PIP_EF) contributes to determine the host specificity of phage HEf13 against various E. faecalis strains. Collectively, these results suggest that phage HEf13 has characteristics of a lytic phage, and is a potential therapeutic agent for treatment or prevention of E. faecalis-associated infectious diseases.

Novel lytic bacteriophages of Klebsiella oxytoca ABG-IAUF-1 as the potential agents for mastitis phage therapy

Mastitis is an inflammation of the mammary gland that occurs when pathogenic microorganisms enter the udder. Even though tremendous advancements in veterinary diagnosis and therapeutics, mastitis is still the most frequent and costly disease of dairy herds overall the world. The purpose of this research was to isolate and identify the lytic phages as a potential method for biological control of bovine mastitis. In this study Klebsiella oxytoca was isolated from contaminated milk samples of Isfahan dairy herds, Isfahan, Iran and characterized as K. oxytoca ABG-IAUF-1 and its 16s-rRNA sequence was deposited in GenBank under the accession numbers of MF175803.1. Then, the four novel specific lytic bacteriophages of K. oxytoca ABG-IAUF-1 from Isfahan public wastewater were isolated and identified. The results of transmission electron microscopy indicated that theses isolated phages were related to Myoviridae and Podoviridae families of bacteriophages. Also the analysis of the growth curve of K. oxytoca ABG-IAUF-1 before and after treatment with lytic phage showed the 97% success rate of the phages in preventing of bacterial growth. This is the first report indicating the use of bacteriophages as the potential agents for eliminating the pathogenic bacteria responsible for bovine mastitis in Iran. The applications of these lytic phages could be an asset for biocontrolling of pathogenic agents in medical and veterinary biotechnology.

Effective inhibition of Salmonella Typhimurium in fresh produce by a phage cocktail targeting multiple host receptors

Salmonella contamination of fresh produce is the primary bacterial cause of a significant number of foodborne outbreaks and infections. Bacteriophages can be used as natural antibacterial agents to control foodborne pathogens. However, the rapid development of bacterial resistance to phage infection is a significant barrier to practical phage application. To overcome this problem, we developed a novel phage cocktail consisting of the three phages (BSPM4, BSP101 and BSP22A) that target different host receptors, including flagella, O-antigen and BtuB, respectively. Whole genome sequence analysis of the phages revealed that three phages do not harbor genes involved in lysogen formation or toxin production, suggesting they are safe for use as biocontrol agents in foods. In vitro treatment of the phage cocktail resulted in a significant reduction in the development of bacterial resistance. Phage cocktail treatments achieved 4.7-5.5 log CFU/cm2 reduction of viable cell number in iceberg lettuce and 4.8-5.8 log CFU/cm2 reduction in cucumber after 12 h at room temperature (25 °C). The phage cocktail exhibited good antimicrobial efficiency, suggesting that it could reduce S. Typhimurium contamination of fresh produce. The strategy of developing cocktails of phages that target multiple host receptors can be used to develop novel biocontrol agents of S. Typhimurium.

Lytic KFS-SE2 phage as a novel bio-receptor for Salmonella Enteritidis detection

Since Salmonella Enteritidis is one of the major foodborne pathogens, on-site applicable rapid detection methods have been required for its control. The purpose of this study was to isolate and purify S. Enteritidis-specific phage (KFS-SE2 phage) from an eel farm and to investigate its feasibility as a novel, efficient, and reliable bio-receptor for its employment. KFS-SE2 phage was successfully isolated at a high concentration of (2.31 ± 0.43) × 10¹¹ PFU/ml, and consisted of an icosahedral head of 65.44 ± 10.08 nm with a non-contractile tail of 135.21 ± 12.41 nm. The morphological and phylogenetic analysis confirmed that it belongs to the Pis4avirus genus in the family of Siphoviridae. KFS-SE2 genome consisted of 48,608 bp with 45.7% of GC content. Genome analysis represented KFS-SE2 to have distinctive characteristics as a novel phage. Comparative analysis of KFS-SE2 phage with closely related strains confirmed its novelty by the presence of unique proteins. KFS-SE2 phage exhibited excellent specificity to S. Enteritidis and was stable under the temperature range of 4 to 50°C and pH of 3 to 11 (P < 0.05). The latent time was determined to be 20 min. Overall, a new lytic KFS-SE2 phage was successfully isolated from the environment at a high concentration and the excellent feasibility of KFS-SE2 phage was demonstrated as a new bio-receptor for S. Enteritidis detection.

Isolation and characterization of a potentially novel Siphoviridae phage (vB_SsapS-104) with lytic activity against Staphylococcus saprophyticus isolated from urinary tract infection

Antibiotic resistance is increasing among Staphylococcus saprophyticus strains isolated from urinary tract infection. This necessitates alternative therapies. For this, a lytic phage (vB_SsapS-104) against S. saprophyticus, which formed round and clear plaques on bacterial culture plates, was isolated from hospital wastewater and characterized. Microscopy analysis showed that it had a small head (about 50 nm), tail (about 80 nm), and a collar (about 22 nm in length and 19 nm in width) indicating to be a phage within Siphoviridae family. Phage vB_SsapS-104 showed a large latency period of about 40 min, rapid adsorption rate that was significantly enhanced by MgCl₂ and CaCl₂, and high stability to a wide range of temperatures and pH values. Restriction analyses demonstrated that phage consists of a double-stranded DNA with an approximate genome size of 40 Kb. BLAST results did not show high similarity (megablast) with other previously identified phages. But, in Blastn, similarity with Staphylococcus phages was observed. Phage vB_SsapS-104 represented high anti-bacterial activity against S. saprophyticus isolates in vitro as it was able to lyse 8 of the 9 clinical isolates (%88.8) obtained from a hospital in Gorgan, Iran. It was a S. saprophyticus-specific phage because no lytic activity was observed on some other pathogenic bacteria tested. Therefore, phage vB_SsapS-104 can be considered as a specific virulent phage against of S. saprophyitcus isolated from urinary tract infection. This study provided the partial genomic characterization of S. saprophyticus phage and its application against urinary tract infection associated with S. saprophyticus. This phage also can be considered as a good candidate for a therapeutic alternative in the future.

Isolation and characterization of two lytic bacteriophages against Staphylococcus aureus from India: newer therapeutic agents against Bovine mastitis

Bovine mastitis causes severe economic losses to dairy farmers. Staphylococcus aureus, is one of the most important pathogen implicated in etiology of clinical and subclinical mastitis in bovines. In view of increasing antimicrobial resistance alternatives to antibiotic therapy are much needed. The present decade has witnessed a renewed interest in phage based therapeutics and diagnostics. The present study, describes isolation and characterization of two lytic phages SAJK-IND and MSP against Staphylococcus aureus having a potential to be used in therapy against mastitis. SAJK-IND and MSP phages belonged to Myoviridae and Podoviridae families, respectively. TEM imaging of the two phages revealed an iscosahedral head. MSP phage has a short non contractile tail. SAJK-IND and MSP have a burst size of 44 ± 3 and 25 ± 5 PFU/ infected cell, respectively. SAJK-IND and MSP phages revealed ̴ 12 and ̴16 proteins, respectively on SDS-PAGE analysis. The lytic activity of the phages was specific for Staphylococcus aureus. SAJK-IND revealed 100% lytic activity against several strains of Staphylococcus aureus isolated from mastitis milk samples whereas, MSP had only 40% lytic activity. SAJK-IND phage genome was sequenced, assembled and deposited in Genbank under accession no MG010123.

Reduction of Salmonella in ground chicken using a bacteriophage

This study's goal was to ascertain the effectiveness of a commercially available Salmonella bacteriophage during ground chicken production focusing on: water source, different Salmonella serovars, and time. Salmonella-free boneless, skinless chicken meat was inoculated with 4.0 Log CFU/cm2 of either a cocktail of 3 Salmonella isolates derived from ground chicken (GC) or a cocktail of 3 Salmonella strains not isolated from ground chicken (non-GC). Bacteriophages were spread onto the chicken using sterile tap or filtered water for 30 min or 8 h. Salmonella was recovered using standard plating method. Greater Salmonella reduction was observed when the bacteriophage was diluted in sterile tap water than in sterile filtered water: 0.39 Log CFU/cm2 and 0.23 Log CFU/cm2 reduction after 30 min, respectively (P < 0.05). The non-GC isolates showed reductions of 0.71 Log CFU/cm2 and 0.90 Log CFU/cm2 after 30 min and 8 h, respectively (P < 0.05). The GC isolates were less sensitive to the bacteriophage: 0.39 Log CFU/cm2 and 0.67 Log CFU/cm2 reductions after 30 min and 8 h, respectively (P < 0.05). In conclusion, bacteriophage reduction was dependent on water used to dilute the bacteriophage, Salmonella's susceptibility to the bacteriophage, and treatment time.

Isolation and Characterization of a Lytic Bacteriophage (vB_PmiS-TH) and Its Application in Combination with Ampicillin against Planktonic and Biofilm Forms of Isolated from Urinary Tract Infection

<i>Proteus mirabilis</i> is one of the most common causes of urinary tract infection (UTI), particularly in patients undergoing long-term catheterization. Phage vB_PmiS-TH was isolated from wastewater with high lytic activity against <i>P. mirabilis</i> (TH) isolated from UTI. The phage had rapid adsorption, a large burst size (∼260 PFU per infected cell), and high stability at a wide range of temperatures and pH values. As analyzed by transmission electron microscopy, phage vB_PmiS-TH had an icosahedral head of ∼87 × 62 nm with a noncontractile tail about 137 nm in length and 11 nm in width. It belongs to the family <i>Siphoviridae</i>. Combination of the phage vB_PmiS-TH with ampicillin had a higher removal activity against planktonic cells of <i>P. mirabilis</i> (TH) than the phage or the antibiotic alone. Combination of the phage at a multiplicity of infection of 100 with a high dose of ampicillin (246 µg/mL) showed the highest biofilm removal activity after 24 h. This study demonstrates that using a combination of phage and antibiotic could be significantly more effective against planktonic and biofilm forms of <i>P. mirabilis</i> (TH).

The role of staphylococci in subclinical mastitis of cows and lytic phage isolation against to Staphylococcus aureus

Aim:

This study was conducted to determine the role of Staphylococcus in the formation of subclinical mastitis in cows and to isolate the phage against isolated Staphylococcus aureus strains.

Materials and Methods:

In this study, 400 milk cows were screened by California Mastitis Test (CMT) for subclinical mastitis and 235 udders of 96 cows, which were determined to be positive, were evaluated for Staphylococcus. Milk samples were evaluated using conventional and molecular methods. In addition, phage isolation studies were performed against S. aureus strains causing mastitis.

Results:

At the result of cultural examination, of 235 milk samples that were found as positive for mastitis by CMT, a total of 117 (49.7%) Staphylococcus spp. were isolated as a distribution of 74 (63.24%) coagulase-positive staphylococci and 43 (36.75%) coagulase-negative staphylococci. Of these isolates, 76 (64.95%) were characterized as S. aureus both conventional and molecular techniques. Lytic bacteriophages against two S. aureus strains which were isolated from mastitic milk samples were obtained from wastewater samples.

Conclusion:

The results of this study show that a significant portion of subclinical mastitis was formed by staphylococci. In addition, phage isolation against S. aureus strains isolated can be considered as one of the steps to be applied in the prophylaxis and treatment of such infections.

Isolation of Potential Phages against Multidrug-Resistant Bacterial Isolates: Promising Agents in the Rivers of Kathmandu, Nepal

Bacteriophages are being the subject of interest for alternative antimicrobial therapy for infectious diseases in recent years. Therapeutic effectiveness regarding phage therapy is a matter of concern since it is the most promising biological treatment of this era. Hence, the present study was aimed to isolate the potential bacteriophages present in river water samples and to analyze their host range among clinical strains of bacteria. Ten different locations of Kathmandu valley were selected for the collection of river water for the detection of probable phages. Bacteriophages were isolated from water samples using the double agar overlay method. Isolated phages were purified by diluting in the SM-buffer and filtering through 0.22 μm filter. Purified lysate was further processed for analyzing its host range by using spot method. Their host range was characterized against 20 bacterial strains, including multidrug-resistant. Total 67 different phages were isolated against 8 different host organisms. Out of them, forty-seven phages were selected for analyzing its host range. Among them, Serratia phages (ΦSER) had the broad host range infecting 17 different bacterial strains including multidrug-resistant harboring ESBL and MBL genotypes. However, Klebsiella phages (ΦKP) had narrow host range in comparison to other phages. Isolated phages had the potential effect against clinical strains of bacteria along with their broader host spectrum. Most importantly, promising effect against MDR pathogens in this study has raised the probable chances of the utility of these phages for biological control of bacterial infection including MBL and ESBL strains.

Broad-range lytic bacteriophages that kill Staphylococcus aureus local field strains

Staphylococcus aureus is a very successful opportunistic pathogen capable of causing a variety of diseases ranging from mild skin infections to life-threatening sepsis, meningitis and pneumonia. Its ability to display numerous virulence mechanisms matches its skill to display resistance to several antibiotics, including β-lactams, underscoring the fact that new anti-S. aureus drugs are urgently required. In this scenario, the utilization of lytic bacteriophages that kill bacteria in a genus -or even species- specific way, has become an attractive field of study. In this report, we describe the isolation, characterization and sequencing of phages capable of killing S. aureus including methicillin resistant (MRSA) and multi-drug resistant S. aureus local strains from environmental, animal and human origin. Genome sequencing and bio-informatics analysis showed the absence of genes encoding virulence factors, toxins or antibiotic resistance determinants. Of note, there was a high similarity between our set of phages to others described in the literature such as phage K. Considering that reported phages were obtained in different continents, it seems plausible that there is a commonality of genetic features that are needed for optimum, broad host range anti-staphylococcal activity of these related phages. Importantly, the high activity and broad host range of one of our phages underscores its promising value to control the presence of S. aureus in fomites, industry and hospital environments and eventually on animal and human skin. The development of a cocktail of the reported lytic phages active against S. aureus–currently under way- is thus, a sensible strategy against this pathogen.

Efficacy of potential phage cocktails against Vibrio harveyi and closely related Vibrio species isolated from shrimp aquaculture environment in the south east coast of India

A diverse set of novel phages infecting the marine pathogenic Vibrio harveyi was isolated from shrimp aquaculture environments in the south east coast of India. Based on initial screening, three phages with a broad host range revealed that the growth inhibition of phage is relatively specific to V. harveyi. They were also able to infect V. alginolyticus and V. parahemolyticus that belonged to the Harveyi clade species from shrimp pond and sea coast environment samples. However, the impact of these phages on their host bacterium are well understood; a one-step growth curve experiment and transmission electron microscope (TEM) revealed three phages grouped under the Myoviridae (VHM1 and VHM2); Siphoviridae (VHS1) family. These phages were further molecular characterized with respect to phage genomic DNA isolates. The randomly amplified polymorphic DNA (RAPD), restriction fragment length polymorphism (RFLP) digestion with HindIII, and major structural proteins were distinguished by sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) clearly indicated that all the phage isolates were different, even when they came from the same source, giving an insight into the diversity of phages. Evaluation of microcosm studies of Penaeus monodon larvae infected with V. harveyi (105 CFU mL-1) showed that larvae survival after 96 h in the presence of phage treatment at 109 PFU mL-1 was enhanced when compared with the control. The resolution in over survival highly recommended that this study provides the phage-based therapy which could be an innovative and eco-friendly solution against Vibrio disease in shrimp aquaculture and in the natural environment.

A Novel Staphylococcus Podophage Encodes a Unique Lysin with Unusual Modular Design

Drug-resistant staphylococci, particularly Staphylococcus aureus and Staphylococcus epidermidis, are leading causes of hospital-acquired infections. Bacteriophages and their peptidoglycan hydrolytic enzymes (lysins) are currently being explored as alternatives to conventional antibiotics; however, only a limited diversity of staphylococcal phages and their lysins has yet been characterized. Here, we describe a novel staphylococcal phage and its lysins. Bacteriophage Andhra is the first reported S. epidermidis phage belonging to the family Podoviridae. Andhra possesses an 18,546-nucleotide genome with 20 open reading frames. BLASTp searches revealed that gene product 10 (gp10) and gp14 harbor putative catalytic domains with predicted peptidase and amidase activities, characteristic functions of phage lysins. We purified these proteins and show that both Andhra_gp10 and Andhra_gp14 inhibit growth and degrade cell walls of diverse staphylococci, with Andhra_gp10 exhibiting more robust activity against the panel of cell wall substrates tested. Site-directed mutagenesis of its predicted catalytic residues abrogated the activity of Andhra_gp10, consistent with the presence of a catalytic CHAP domain on its C terminus. The active site location combined with the absence of an SH3b cell wall binding domain distinguishes Andhra_gp10 from the majority of staphylococcal lysins characterized to date. Importantly, close homologs of Andhra_gp10 are present in related staphylococcal podophages, and we propose that these constitute a new class of phage-encoded lysins. Altogether, our results reveal insights into the biology of a rare family of staphylococcal phages while adding to the arsenal of antimicrobials with potential for therapeutic use. IMPORTANCE The spread of antibiotic resistance among bacterial pathogens is inciting a global public health crisis. Drug-resistant Staphylococcus species, especially S. aureus and S. epidermidis, have emerged in both hospital and community settings, underscoring the urgent need for new strategies to combat staphylococcal infections. Bacterial viruses (phages) and the enzymes that they use to degrade bacterial cell walls (lysins) show promise as alternative antimicrobials; however, only a limited variety of staphylococcal phages and their lysins have yet been identified. Here, we report the discovery and characterization of a novel staphylococcal phage, Andhra. We show that Andhra encodes two lysins (Andhra_gp10 and Andhra_gp14) that inhibit growth and degrade the cell walls of diverse staphylococci, including S. aureus and S. epidermidis strains. Andhra and its unique lysins add to the arsenal of antimicrobials with potential for therapeutic use.

Characterization of potential lytic bacteriophage against Vibrio alginolyticus and its therapeutic implications on biofilm dispersal

Vibrio alginolyticus is a leading cause of vibriosis, presenting opportunistic infections to humans associated with raw seafood contamination. At present, phage therapy that acts as an alternative sanitizing agent is explored for targeting V. alginolyticus. The study outcome revealed that the phage VP01 with its extreme lytic effect showed a high potential impact on the growth of V. alginolyticus as well as biofilm formation. Electron microscopy revealed the phage resemblance to Myoviridae, based on its morphology. Further study clarified that the phage VP01 possesses a broad host spectrum and amazing phage sensitivity at different pH, high thermal stability, and high burst size of 415 PFU/cell. In addition, the investigation of phage co-culturing against this pathogen resulted in a significant growth reduction even at less MOIs 0.1 and 1. These results suggest that the phage could be a promising candidate for the control of V. alginolyticus infections.

Genomic and proteomic characterization of SE-I, a temperate bacteriophage infecting Erysipelothrix rhusiopathiae

A bacteriophage infecting pathogenic Erysipelothrix rhusiopathiae was isolated from a swine farm experiencing an outbreak of acute swine erysipelas; we designated this phage SE-I. SE-I has an icosahedral head, a long tail and a double-stranded DNA genome. The 34,997-bp genome has a GC content of 34 % and contains 43 open reading frames (ORFs) encoding packaging, structural, lysin-holin, and hypothetical proteins. Components of purified SE-I were separated using SDS-PAGE and analyzed using liquid chromatography-mass spectrometry. Nine proteins were identified, encoded by ORF9, ORF15, ORF23, ORF30, ORF31, ORF33, ORF39, ORF40 and ORF 42. A phylogenetic tree constructed based on the sequence of the large terminase subunit revealed that SE-I is closely related to Staphylococcus phages P954 and phi3396. The CHAP-domain-containing protein encoded by ORF25 was expressed in E. coli and which was able to inactivate host bacteria. SE-I was able to infect 7 of 13 E. rhusiopathiae strains, but was unable to infect Salmonella, Streptococcus suis, and Staphylococcus aureus. This is the first report of the isolation, characterization, and genomic and proteomic analysis of a temperate phage infecting E. rhusiopathiae, and it might lead to the development of new anti- E. rhusiopathiae agents.