Isolation and Molecular Characterization of a Novel Lytic Bacteriophage That Inactivates MDR Klebsiella pneumoniae Strains

Revisiting therapeutic options against resistant klebsiella pneumoniae infection: Phage therapy is key

Multi-drug resistant and carbapenem-resistant hypervirulent Klebsiella pneumoniae strains are spreading globally at an alarming rate, emerging as one of the most serious threats to global public health. The formidable challenges posed by the current arsenal of antimicrobials highlight the urgent need for novel strategies to combat K. pneumoniae infections. This review begins with a comprehensive analysis of the global dissemination of virulence factors and critical resistance profiles in K. pneumoniae, followed by an evaluation of the accessibility of novel therapeutic approaches for treating K. pneumoniae in clinical settings. Among these, phage therapy stands out for its considerable potential in addressing life-threatening K. pneumoniae infections. We critically examine the existing preclinical and clinical evidence supporting phage therapy, identifying key limitations that impede its broader clinical adoption. Additionally, we rigorously explore the role of genetic engineering in expanding the host range of K. pneumoniae phages, and discuss the future trajectory of this technology. In light of the 'Bad Bugs, No Drugs' era, we advocate leveraging artificial intelligence and deep learning to optimize and expand the application of phage therapy, representing a crucial advancement in the fight against the escalating threat of K. pneumoniae infections.

Analysis of a novel phage as a promising biological agent targeting multidrug resistant Klebsiella pneumoniae

The rise of deaths by resistant bacteria is a global threat to public health systems. Klebsiella pneumoniae is a virulent pathogen that causes serious nosocomial infections. The major obstacle to bacterial treatment is antibiotic resistance, which necessitates the introducing of alternative therapies. Phage therapy has been regarded as a promising avenue to fight multidrug-resistant (MDR) pathogens. In the current study, a novel phage vB_KpnP_KP17 was isolated from sewage, and its lytic potential was investigated against K. pneumoniae. The isolated phage vB_KpnP_kP17 was lytic to 17.5% of tested K. pneumoniae isolates. One step growth curve indicated a virulent phage with a short latent period (20 min) and large burst size (331 PFU/cell). Additionally, vB_KpnP_kP17 maintained its activity against planktonic cells over a wide range of pH, temperature and UV irradiation intervals. The potential of vB_KpnP_KP17 as antibiofilm agent was revealed by the biofilm inhibition assay. The isolated phage vB_KpnP_KP17 at multiplicity of infection (MOI) of 10 inhibited more than 50% of attached biofilms of tested K. pneumoniae isolates. The genome of vB_KpnP_kP17 was characterized and found to be a linear dsDNA of 39,936 bp in length and GC content of 52.85%. Additionally, the absence of toxicity, virulence and antibiotic resistance genes further confirms the safety of vB_KpnP_KP17 for clinical applications. These characteristics make vB_KpnP_KP17 of a potential therapeutic value to manage MDR K. pneumoniae infections. Additionally, the formulation of vB_KpnP_KP17 in a cocktail with other lytic phages or with antibiotics could be applied to further limit biofilm-producing K. pneumoniae infections.

Potential of a newly isolated lytic bacteriophage to control Pseudomonas coronafaciens pv. garcae in coffee plants: Molecular characterization with in vitro and ex vivo experiments

Traditionally, control of coffee plant bacterial halo blight (BHB) caused by the phytopathogen Pseudomonas coronafaciens pv. garcae (Pcg) involves frequent spraying of coffee plantations with non-environmentally friendly and potentially bacterial resistance-promoting copper products or with kasugamycin hydrochloride. In this study we report a leap forward in the quest for a new ecofriendly approach, characterizing (both physicochemically and biologically) and testing both in vitro and ex vivo a new lytic phage for Pcg. An in-depth molecular (genomic and DNA structural features) characterization of the phage was also undertaken. Phage PcgS01F belongs to the class Caudoviricetes, Drexlerviridae family and genus Guelphvirus, and presents a siphovirus-like morphotype. Phage PcgS01F showed a latency period of 40 min and a burst size of 46 PFU/host cell, allowing to conclude that it replicates well in Pcg IBSBF-158. At Multiplicity Of Infection (MOI, or the ratio of phage to bacteria) 1000, the performance of phage PcgS01F was much better than at MOI 10, promoting increasing bacterial reductions until the end of the in vitro inactivation assays, stabilizing at a significant 82 % bacterial load reduction. Phage PcgS01F infected and killed Pcg cells ex vivo in coffee plant leaves artificially contaminated, with a maximum of Pcg inactivation of 7.66 log CFU/mL at MOI 1000 after 36 h of incubation. This study provides evidence that the isolated phage is a promising candidate against the causative agent of BHB in coffee plants.

Combating enteropathogenic and multidrug resistant Escherichia coli using the lytic bacteriophage vB_EcoM_ECO78, which disrupts bacterial biofilm formation and exhibits a remarkable environmental stability

AIM

The current study aimed to establish a phenotypic and genotypic characterization record of a novel lytic bacteriophage (phage) against multidrug-resistant (MDR) Escherichia coli (E. coli) infections.

METHODS AND RESULTS

Phenotypic characterization of the isolated phage included the assessment of phage morphology, host range, stability, and antibiofilm activity. The isolated phage vB_EcoM_ECO78 demonstrated a high lytic activity against MDR E. coli and E. coli serotypes O78: K80: H12 and O26: H11. Additionally, it showed a marked antibiofilm activity and high physical stability at a wide range of temperatures and pH. Genotypic investigations identified a double-stranded DNA genome of 165 912 base pairs (bp) spanning 258 open reading frames (ORFs), out of which 149 ORFs were identified and annotated. In vivo analysis further confirmed the therapeutic potential of vB_EcoM_ECO78 which effectively increased the survival of mice infected with MDR E. coli.

CONCLUSION

The isolated phage vB_EcoM_ECO78 exhibits considerable stability and antibiofilm activity against MDR E. coli isolates, supported by notable environmental fitness and in vivo antibacterial capability.

High activity and specificity of bacteriophage cocktails against carbapenem-resistant Klebsiella pneumoniae belonging to the high-risk clones CG258 and ST307

Introduction

The widespread clinical and environmental dissemination of successful clones of carbapenem-resistant Klebsiella pneumoniae (CRKP) represents a serious global public health threat. In this context, lytic bacteriophages have emerged as a promising alternative for controlling these pathogens. This study describes the biological, structural, and genomic characteristics of lytic bacteriophages against the high-risk CRKP clones CG258 and ST307 and describes their performance in combination.

Methods

An experimental study was carried out. Bacteriophages were isolated from hospital wastewater and from wastewater treatment plants (WWTP). Bacteriophages were isolated using the double layer agar technique and their characterization included host range (individual and cocktail), plating efficiency (EOP), infection or bacterial killing curve, one-step curve, bacteriophage stability at pH and temperature conditions, transmission electron microscopy (TEM) and whole genome sequencing.

Results

After purification, five active bacteriophages against CRKP were obtained, three bacteriophages (FKP3, FKP4 and FKP14) had targeted activities against CG258 CRKP and two (FKP10 and FKP12) against ST307 isolates. Seven cocktails were prepared, of which Cocktail 2, made up of the bacteriophages FKP3, FKP10, and FKP14, showed the best activity against 85.7% (n = 36/42) of CRKP isolates belonging to both clones, CG258 (80.8%; n = 21/26) and ST307 (93.8%, n = 15/16). The efficiency of the plating (EOP), infection curve, and one-step growth curve showed that the cocktail phages efficiently infected other CRKP isolates (EOP ≥ 0.5), controlled bacterial growth up to 73.5%, and had short latency periods, respectively, (5-10 min). In addition, they were stable at temperatures between 4°C and 50°C and pH between 4 and 10. All bacteriophages belonged to the Caudoviricetes class, and no genes associated with virulence factors or antibiotic resistance were detected.

Conclusion

These findings showed bacteriophages and phage cocktails with high specificity against CRKP belonging to the successful clones CG258 and ST307 with promising characteristics, making them an alternative for controlling these clones in different environmental or health settings, biocontrol agents, or disinfectants in industry and in the field of diagnosis.

A New Casjensviridae Bacteriophage Isolated from Hospital Sewage for Inactivation of Biofilms of Carbapenem Resistant Klebsiella pneumoniae Clinical Isolates

Klebsiella pneumoniae, a member of the ESKAPE pathogen group, is a prominent cause of hospital-acquired infections. The WHO has recognized carbapenem-resistant K. pneumoniae as a critical-one priority pathogen. These resilient superbugs have the ability to form biofilms and present a significant global threat. In the present study, we isolated and characterized a bacteriophage SAKp02, from hospital sewage, infectious to carbapenem-resistant K. pneumoniae patient isolates. SAKp02 could infect 43 of 72 clinical isolates, indicating a broad host spectrum. Whole genome analysis classified SAKp02 within the family Casjensviridae, with a 59,343 bp genome encoding 82 ORFs. Comparative genomic analysis revealed significant differences between SAKp02 and its closest viruses, indicating a distinct genetic makeup positioning it as a novel phage strain within the lineage. The SAKp02 genome comprises bacteriolytic enzymes, including holin, endolysin, and phage depolymerase, crucial for bacterial lysis and biofilm disruption. It reduced biofilm biomass by over threefold compared to the control and eradicated 99% of viable cells within a 4 h treatment period. Scanning electron microscopy corroborated the ability of the phage to dismantle biofilm matrices and lyse bacterial cells. Safe and effective treatments are warranted, and hence, the fully characterized lytic phages with therapeutic potential against drug-resistant clinical isolates of bacteria are needed. Our study is the first to report the antibacterial and antibiofilm activity of Casjensviridae phages, and our discovery of a novel K. pneumoniae phage broadens the arsenal against the bacteria.

Analysis of a new phage, KZag1, infecting biofilm of Klebsiella pneumoniae: genome sequence and characterization

BACKGROUND

This study investigates the effectiveness of the bacteriophage KZag1 against drug-resistant Klebsiella pneumoniae, aiming to assess its potential as a therapeutic agent. The novelty lies in the characterization of KZag1, a Myovirus with specific efficacy against multidrug-resistant K. pneumoniae strains. This highlights the significance of exploring alternative strategies, particularly phage therapy, in addressing biofilm-associated infections.

METHODS

KZag1, characterized by a typical Myovirus structure with a 75 ± 5 nm diameter icosahedral head and a 15 ± 5 nm short tail, was evaluated in experimental trials against 15 strains of K. pneumoniae. The infection cycle duration was determined to be 50 min, resulting in an estimated burst size of approximately 83 plaque-forming units per colony-forming unit (PFU/CFU). Stability assessments were conducted within a pH range of 4 to 12 and temperatures ranging from 45°C to 60°C. Biofilm biomass reduction was observed, particularly at a multiplicity of infection (MOI) of 10.

RESULTS

KZag1 demonstrated infection efficacy against 12 out of 15 tested K. pneumoniae strains. The phage exhibited stability across a broad pH range and at elevated temperatures. Notably, treatment with KZag1 significantly reduced K. pneumoniae biofilm biomass, emphasizing its potential in combating biofilm formation. Genomic analysis revealed a complete genome of 157,089 base pairs with a GC content of 46.38%, encompassing 203 open reading frames (ORFs) and a cysteine-specific tRNA sequence. Comparison with phage GP4 highlighted similarities, with KZag1 having a longer genome by approximately 4829 base pairs and a higher GC content by approximately 0.93%. Phylogenetic analysis classified KZag1 within the Myoviridae family.

CONCLUSION

The efficacy of KZag1 against K. pneumoniae biofilm suggests its potential as a therapeutic candidate, especially for drug-resistant infections. Further clinical research is warranted to explore its synergy with other treatments, elucidate genomic traits, compare with Myoviridae phages, and understand its host interactions. These findings underscore the promising role of KZag1 in addressing drug-resistant bacterial infections.

Potential of an Isolated Bacteriophage to Inactivate Klebsiella pneumoniae: Preliminary Studies to Control Urinary Tract Infections

Urinary tract infections (UTIs) caused by resistant Klebsiella pneumoniae can lead to severe clinical complications and even death. An alternative treatment option for infected patients is using bacteriophages. In the present study, we isolated phage VB_KPM_KP1LMA (KP1LMA) from sewage water using a K. pneumoniae strain as a host. Whole-genome analysis indicated that the genome was a double-stranded linear 176,096-bp long DNA molecule with 41.8% GC content and did not contain virulence or antibiotic resistance genes. The inactivation potential of phage KP1LMA was assessed in broth at an MOI of 1 and 10, and a maximum inactivation of 4.9 and 5.4 log CFU/mL, respectively, was observed after 9 h. The efficacy at an MOI of 10 was also assessed in urine to evaluate the phage's performance in an acidic environment. A maximum inactivation of 3.8 log CFU/mL was observed after 9 h. The results suggest that phage KP1LMA could potentially control a UTI caused by this strain of K. pneumoniae, indicating that the same procedure can be used to control UTIs caused by other strains if new specific phages are isolated. Although phage KP1LMA has a narrow host range, in the future, efforts can be made to expand its spectrum of activity and also to combine this phage with others, potentially enabling its use against other K. pneumoniae strains involved in UTIs.

Molecular Characterization and Genome Mechanical Features of Two Newly Isolated Polyvalent Bacteriophages Infecting Pseudomonas syringae pv. garcae

Coffee plants have been targeted by a devastating bacterial disease, a condition known as bacterial blight, caused by the phytopathogen Pseudomonas syringae pv. garcae (Psg). Conventional treatments of coffee plantations affected by the disease involve frequent spraying with copper- and kasugamycin-derived compounds, but they are both highly toxic to the environment and stimulate the appearance of bacterial resistance. Herein, we report the molecular characterization and mechanical features of the genome of two newly isolated (putative polyvalent) lytic phages for Psg. The isolated phages belong to class Caudoviricetes and present a myovirus-like morphotype belonging to the genuses Tequatrovirus (PsgM02F) and Phapecoctavirus (PsgM04F) of the subfamilies Straboviridae (PsgM02F) and Stephanstirmvirinae (PsgM04F), according to recent bacterial viruses' taxonomy, based on their complete genome sequences. The 165,282 bp (PsgM02F) and 151,205 bp (PsgM04F) genomes do not feature any lysogenic-related (integrase) genes and, hence, can safely be assumed to follow a lytic lifestyle. While phage PsgM02F produced a morphogenesis yield of 124 virions per host cell, phage PsgM04F produced only 12 virions per host cell, indicating that they replicate well in Psg with a 50 min latency period. Genome mechanical analyses established a relationship between genome bendability and virion morphogenesis yield within infected host cells.

Bacteriophages: Vectors of or weapons against the transmission of antibiotic resistance genes in hospital wastewater systems?

Antimicrobial resistance poses a serious threat to human health and is responsible for the death of millions of people annually. Hospital wastewater is an important hotspot for antibiotic-resistance genes (ARGs) and antibiotic-resistant bacteria (ARB). However, little is known about the relationship between phages and ARGs in hospital wastewater systems (HWS). In the present study, the viral diversity of 12 HWSs using data from public metagenomic databases was investigated. Viruses were widely found in both the influent and effluent of each HWS. A total of 45 unique ARGs were carried by 85 viral contigs, which accounted for only 0.14% of the total viral populations, implying that ARGs were not commonly present in phages. Three efflux pump genes were identified as shared between phages and bacterial genomes. However, the predominant types of ARGs in HWS such as aminoglycoside- and beta-lactam-resistance genes were rarely found in phages. Based on CRISPR spacer and tRNA matches, interactions between 171 viral contigs and 60 antibiotic-resistant genomes were predicted, including interactions involving phages and vancomycin-resistant Enterococcus_B faecium or beta-lactam-resistant Klebsiella pneumoniae. More than half (56.1%) of these viral contigs indicated lytic and none of them carried ARGs. As the vOTUs in this study had few ARGs and were primarily lytic, HWS may be a valuable source for phage discovery. Future studies will be able to experimentally validate these sequence-based results to confirm the suitability of HWS phages for pathogen control measures in wastewater.

Newly isolated phages preying on Pseudomonas syringae pv. garcae: In vitro and ex vivo inactivation studies in coffee plant leafs

Coffee canker, or bacterial halo blight (BHB) of coffee, is a disease caused by the phytopathogenic bacterium Pseudomonas syringae pv. garcae (Psg), having been found for the first time in 1955, in the Garça region (State of São Paulo), and which has stood out in the Brazilian coffee plantations in recent years, leading to severe economic losses that seriously affect coffee trade. The treatments available are still scarce, involving frequent spraying of coffee plantations with either copper derivatives or the antibiotic kasugamycin. However, these compounds should be avoided due to environmental toxicity and the development of bacterial resistances. Herein we report the isolation and physical/biological characterisation of two novel lytic phages and their efficacy in the control of Psg. Phages ph002F and ph004F were isolated from coffee plant leaves in Brazil (Sorocaba/SP and Itu/SP cities), using Psg IBSBF-158 as the host. According to the transmission electron microscopy analyses, both phages belong to the class Caudoviricetes and present myovirus-like morphotypes. Phages ph002F and ph004F showed eclipse times of 5 min and 20 min, respectively, and a burst size of 123 PFU/host cell and 12 PFU/host cell, respectively, allowing to conclude they replicate well in Psg IBSBF-158 with latency periods of 50 min. Phage ph002F (reduction of 4.59 log CFU/mL, compared to uninfected culture) was more effective in inactivating Psg than phage ph004F (reduction of 3.85 log CFU/mL) after 10 h of incubation at a MOI of 10. As a cocktail, the two phages were highly effective in reducing the bacterial load (reduction of 5.26 log CFU/mL at a MOI of 0.1 or reduction of 5.03 log CFU/mL at a MOI of 10, relative to untreated culture), after 12 h of treatment. This study provides evidence that the isolated phages are promising candidates against the causative agent of BHB in coffee plants.

Newly Isolated Virulent Salmophages for Biocontrol of Multidrug-Resistant Salmonella in Ready-to-Eat Plant-Based Food

Due to irrational antibiotic stewardship, an increase in the incidence of multidrug resistance of bacteria has been observed recently. Therefore, the search for new therapeutic methods for pathogen infection treatment seems to be necessary. One of the possibilities is the utilization of bacteriophages (phages)—the natural enemies of bacteria. Thus, this study is aimed at the genomic and functional characterization of two newly isolated phages targeting MDR Salmonella enterica strains and their efficacy in salmonellosis biocontrol in raw carrot–apple juice. The Salmonella phage vB_Sen-IAFB3829 (Salmonella phage strain KKP 3829) and Salmonella phage vB_Sen-IAFB3830 (Salmonella phage strain KKP 3830) were isolated against S. I (6,8:l,-:1,7) strain KKP 1762 and S. Typhimurium strain KKP 3080 host strains, respectively. Based on the transmission electron microscopy (TEM) and whole-genome sequencing (WGS) analyses, the viruses were identified as members of tailed bacteriophages from the Caudoviricetes class. Genome sequencing revealed that these phages have linear double-stranded DNA and sizes of 58,992 bp (vB_Sen-IAFB3829) and 50,514 bp (vB_Sen-IAFB3830). Phages retained their activity in a wide range of temperatures (from −20 °C to 60 °C) and active acidity values (pH from 3 to 11). The exposure of phages to UV radiation significantly decreased their activity in proportion to the exposure time. The application of phages to the food matrices significantly reduced the level of Salmonella contamination compared to the control. Genome analysis showed that both phages do not encode virulence or toxin genes and can be classified as virulent bacteriophages. Virulent characteristics and no possible pathogen factors make examined phages feasible to be potential candidates for food biocontrol.

New Bacteriophages Members of the Ackermannviridae Family Specific for Klebsiella pneumoniae ST258

Background

Carbapenem-resistant Klebsiella pneumoniae, particularly isolates classified as sequence-type 258 (ST258), are multidrug-resistant strains that are strongly associated with poor-prognosis nosocomial infections, as current therapeutic options are limited and ineffective. In recent years, phage therapy has emerged as a promising treatment option for these scenarios.

Methodology and Results

We report the isolation and characterization of three new phages against Klebsiella pneumoniae ST258 strains recovered from Machángara river wastewater. These new members of the Ackermannviridae family showed stability over a wide temperature and pH range and burst sizes ranging from 6 to 44 plaque-forming units per bacteria. Their genomes were about 157 kilobases, with an average guanine-cytosine content of 46.4% and showed presence of several transfer RNAs, which also allowed us to predict in silico a lytic replicative cycle due to the presence of endolysins and lysozymes.

Conclusion

Three lytic phages of Ackermannviridae family were recovered against Klebsiella pneumoniae ST258 strains from sewage; however, further characterization is needed for future consideration as therapeutic alternatives.

An Edible Biopolymeric Microcapsular Wrapping Integrating Lytic Bacteriophage Particles for Salmonella enterica: Potential for Integration into Poultry Feed

This research work aimed at developing an edible biopolymeric microcapsular wrapping (EBMW) integrating lytic bacteriophage particles for Salmonella enterica, with potential application in poultry feed for biocontrol of that pathogen. This pathogen is known as one of the main microorganisms responsible for contamination in the food industry and in foodstuff. The current techniques for decontamination and pathogen control in the food industry can be very expensive, not very selective, and even outdated, such as the use of broad-spectrum antibiotics that end up selecting resistant bacteria. Hence, there is a need for new technologies for pathogen biocontrol. In this context, bacteriophage-based biocontrol appears as a potential alternative. As a cocktail, both phages were able to significantly reduce the bacterial load after 12 h of treatment, at either multiplicity of infection (MOI) 1 and 10, by 84.3% and 87.6%, respectively. Entrapment of the phage virions within the EBMW matrix did not exert any deleterious effect upon their lytic activity. The results obtained showed high promise for integration in poultry feed aiming at controlling Salmonella enterica, since the edible biopolymeric microcapsular wrapping integrating lytic bacteriophage particles developed was successful in maintaining lytic phage viability while fully stabilizing the phage particles.

The Lytic Activity of Bacteriophage ZCSE9 against Salmonella enterica and Its Synergistic Effects with Kanamycin

Salmonella, the causative agent of several diseases in humans and animals, including salmonellosis, septicemia, typhoid fever, and fowl typhoid, poses a serious threat to global public health and food safety. Globally, reports of therapeutic failures are increasing because of the increase in bacterial antibiotic resistance. Thus, this work highlights the combined phage–antibiotic therapy as a promising approach to combating bacterial resistance. In this manner, the phage ZCSE9 was isolated, and the morphology, host infectivity, killing curve, combination with kanamycin, and genome analysis of this phage were all examined. Morphologically, phage ZCSE9 is a siphovirus with a relatively broad host range. In addition, the phage can tolerate high temperatures until 80 °C with one log reduction and a basic environment (pH 11) without a significant decline. Furthermore, the phage prevents bacterial growth in the planktonic state, according to the results of the time-killing curve. Moreover, using the phage at MOI 0.1 with kanamycin against five different Salmonella serotypes reduces the required antibiotics to inhibit the growth of the bacteria. Comparative genomics and phylogenetic analysis suggested that phage ZCSE9, along with its close relatives Salmonella phages vB_SenS_AG11 and wksl3, belongs to the genus Jerseyvirus. In conclusion, phage ZCSE9 and kanamycin form a robust heterologous antibacterial combination that enhances the effectiveness of a phage-only approach for combating Salmonella.

Characterization and comprehensive genome analysis of novel bacteriophage, vB_Kpn_ZCKp20p, with lytic and anti-biofilm potential against clinical multidrug-resistant Klebsiella pneumoniae

Introduction

The rise of infections by antibiotic-resistant bacterial pathogens is alarming. Among these, Klebsiella pneumoniae is a leading cause of death by hospital-acquired infections, and its multidrug-resistant strains are flagged as a global threat to human health, which necessitates finding novel antibiotics or alternative therapies. One promising therapeutic alternative is the use of virulent bacteriophages, which specifically target bacteria and coevolve with them to overcome potential resistance. Here, we aimed to discover specific bacteriophages with therapeutic potential against multiresistant K. pneumoniae clinical isolates.

Methods and Results

Out of six bacteriophages that we isolated from urban and medical sewage, phage vB_Kpn_ZCKp20p had the broadest host range and was thus characterized in detail. Transmission electron microscopy suggests vB_Kpn_ZCKp20p to be a tailed phage of the siphoviral morphotype. In vitro evaluation indicated a high lytic efficiency (30 min latent period and burst size of ∼100 PFU/cell), and extended stability at temperatures up to 70°C and a wide range of (2-12) pH. Additionally, phage vB_Kpn_ZCKp20p possesses antibiofilm activity that was evaluated by the crystal violet assay and was not cytotoxic to human skin fibroblasts. The whole genome was sequenced and annotated, uncovering one tRNA gene and 33 genes encoding proteins with assigned functions out of 85 predicted genes. Furthermore, comparative genomics and phylogenetic analysis suggest that vB_Kpn_ZCKp20p most likely represents a new species, but belongs to the same genus as Klebsiella phages ZCKP8 and 6691. Comprehensive genomic and bioinformatics analyses substantiate the safety of the phage and its strictly lytic lifestyle.

Conclusion

Phage vB_Kpn_ZCKp20p is a novel phage with potential to be used against biofilm-forming K. pneumoniae and could be a promising source for antibacterial and antibiofilm products, which will be individually studied experimentally in future studies.

Isolation and Molecular Characterization of Two Novel Lytic Bacteriophages for the Biocontrol of Escherichia coli in Uterine Infections: In Vitro and Ex Vivo Preliminary Studies in Veterinary Medicine

E. coli is one of the etiological agents responsible for pyometra in female dogs, with conventional treatment involving ovariohysterectomy. Here, we report the isolation and full characterization of two novel lytic phages, viz. vB_EcoM_Uniso11 (ph0011) and vB_EcoM_Uniso21 (ph0021). Both phages belong to the order Caudovirales and present myovirus-like morphotypes, with phage ph0011 being classified as Myoviridae genus Asteriusvirus and phage ph0021 being classified as Myoviridae genus Tequatrovirus, based on their complete genome sequences. The 348,288 bp phage ph0011 and 165,222 bp phage ph0021 genomes do not encode toxins, integrases or antimicrobial resistance genes neither depolymerases related sequences. Both phages were shown to be effective against at least twelve E. coli clinical isolates in in vitro antibacterial activity assays. Based on their features, both phages have potential for controlling pyometra infections caused by E. coli. Phage ph0011 (reduction of 4.24 log CFU/mL) was more effective than phage ph0021 (reduction of 1.90 log CFU/mL) after 12 h of incubation at MOI 1000. As a cocktail, the two phages were highly effective in reducing the bacterial load (reduction of 5.57 log CFU/mL) at MOI 100, after 12 h of treatment. Both phages were structurally and functionally stabilized in vaginal egg formulations.

A Phage Cocktail To Control Surface Colonization by Proteus mirabilis in Catheter-Associated Urinary Tract Infections

Proteus mirabilis is a biofilm-forming bacterium and one of the most common causes of catheter-associated urinary tract infections (CAUTIs). The rapid spread of multidrug-resistant P. mirabilis represents a severe threat to management of nosocomial infections. This study aimed to isolate a potent phage cocktail and assess its potential to control urinary tract infections caused by biofilm-forming P. mirabilis. Two lytic phages, Isf-Pm1 and Isf-Pm2, were isolated and characterized by proteome analysis, transmission electron microscopy, and whole-genome sequencing. The host range and effect of the phage cocktail to reduce the biofilm formation were assessed by a cell adhesion assay in Vero cells and a phantom bladder model. The samples treated with the phage cocktail showed a significant reduction (65%) in the biofilm mass. Anti-quorum sensing and quantitative real-time PCR assays were also used to assess the amounts of transcription of genes involved in quorum sensing and biofilm formation. Furthermore, the phage-treated samples showed a downregulation of genes involved in the biofilm formation. In conclusion, these results highlight the efficacy of two isolated phages to control the biofilms produced by P. mirabilis CAUTIs. IMPORTANCE The rapid spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) bacterial strains and biofilm formation of bacteria have severely restricted the use of antibiotics and become a challenging issue in hospitals. Therefore, there is a necessity for alternative or complementary treatment measures, such as the use of virulent bacteriophages (phages), as effective therapeutic strategies.