Isolation and Characterization of a Novel myovirus Infecting Shigella dysenteriae from the Aeration Tank Water

Bacteriophages as a potential substitute for antibiotics: A comprehensive review

Over the years, the administration of antibiotics for the purpose of addressing bacterial infections has become increasingly challenging due to the increased prevalence of antimicrobial resistance exhibited by various strains of bacteria. Multidrug-resistant (MDR) bacterial species are rising due to the unavailability of novel antibiotics, leading to higher mortality rates. With these conditions, there is a need for alternatives in which phage therapy has made promising results. Phage-derived endolysins, phage cocktails, and bioengineered phages are effective and have antimicrobial properties against MDR and extensively drug-resistant strains. Despite these, it has been observed that phages can give antimicrobial activity to more than one bacterial species. Thus, phage cocktail against resistant strains provides broad spectrum treatment and magnitude of effectivity, which is many folds higher than antibiotics. Many commercially available endolysins such as Staphefekt SA.100, Exebacase (CF-301), and N-Rephasin®SAL200 are used in biofilm penetration and treating plant diseases. The role of CMP1 phage endolysin in transgenic tomato plants in preventing Clavibacter michiganensis infection and the effectiveness of phage in protecting Atlantic salmon from vibriosis have been reported. Furthermore, phage-derived endolysin therapy, such as TSPphg phage exogenous treatment, can aid in disrupting cell walls, leading to bacterial cell lysis. As animals in aquaculture and slaughterhouses are highly susceptible to bacterial infections, effective phage therapy instead of antibiotics can help treat poultry animals, preserve them, and facilitate disease-free trade. Using bioengineered phages and phage cocktails enhances the effectiveness by providing a broad spectrum of phages and target specificity. Research is currently being conducted on clinical trials to confirm the efficacy of engineered phages and phage cocktails in humans. Although obtaining commercial approval may be time-consuming, it will be beneficial in the postantibiotic era. This review provides an overview of the significance of phage therapy as a potential alternative to antibiotics in combating resistant bacterial strains and its application to various fields and emphasizes the importance of safeguarding and ensuring treatment efficacy.

Synergistic action of phages and lytic proteins with antibiotics: a combination strategy to target bacteria and biofilms

BACKGROUND

Multidrug-resistant bacteria continue to emerge owing to the abuse of antibiotics and have a considerable negative impact on people and the environment. Bacteria can easily form biofilms to improve their survival, which reduces the efficacy of antibacterial drugs. Proteins such as endolysins and holins have been shown to have good antibacterial activity and effectively removal bacterial biofilms and reduce the production of drug-resistant bacteria. Recently, phages and their encoded lytic proteins have attracted attention as potential alternative antimicrobial agents. The aim of the present study was to investigate the sterilising efficacy of phages (SSE1, SGF2, and SGF3) and their encoded lytic proteins (lysozyme and holin), and to further explore their potential in combination with antibiotics. To the ultimate aim is to reduce or replace the use of antibiotics and provide more materials and options for sterilisation.

RESULTS

Phages and their encoded lytic proteins were confirmed to have great advantages in sterilisation, and all exhibited significant potential for reducing bacterial resistance. Previous studies on the host spectrum demonstrated the bactericidal efficacy of three Shigella phages (SSE1, SGF2, and SGF3) and two lytic proteins (LysSSE1 and HolSSE1). In this study, we investigated the bactericidal effects on planktonic bacteria and bacterial biofilms. A combined sterilisation application of antibiotics, phages, and lytic proteins was performed. The results showed that phages and lytic proteins had better sterilisation effects than antibiotics with 1/2 minimum inhibitory concentrations (MIC) and their effect was further improved when used together with antibiotics. The best synergy was shown when combined with β- lactam antibiotics, which might be related to their mechanism of sterilising action. This approach ensures a bactericidal effect at low antibiotic concentrations.

CONCLUSIONS

This study strengthens the idea that phages and lytic proteins can significantly sterilise bacteria in vitro and achieve synergistic sterilisation effects with specific antibiotics. Therefore, a suitable combination strategy may decrease the risk of drug resistance.

Recent Advances in the Application of Bacteriophages against Common Foodborne Pathogens

Bacteriophage potential in combating bacterial pathogens has been recognized nearly since the moment of discovery of these viruses at the beginning of the 20th century. Interest in phage application, which initially focused on medical treatments, rapidly spread throughout different biotechnological and industrial fields. This includes the food safety sector in which the presence of pathogens poses an explicit threat to consumers. This is also the field in which commercialization of phage-based products shows the greatest progress. Application of bacteriophages has gained special attention particularly in recent years, presumably due to the potential of conventional antibacterial strategies being exhausted. In this review, we present recent findings regarding phage application in fighting major foodborne pathogens, including Salmonella spp., Escherichia coli, Yersinia spp., Campylobacter jejuni and Listeria monocytogenes. We also discuss advantages of bacteriophage use and challenges facing phage-based antibacterial strategies, particularly in the context of their widespread application in food safety.

Isolation and characterization of SGF3, a novel Microviridae phage infecting Shigella flexneri

In the context of widespread bacterial contamination and the endless emergence of antibiotic-resistant bacteria, more effective ways to control pathogen infection are urgently needed. Phages become potential bactericidal agents due to their bactericidal specificity and not easy resistance to bacteria. But an important factor limiting its development is the lack of phage species. Therefore, the isolation of more new phages and studying their biological and genomic characteristics is of great significance for subsequent applications. So, in this study, SGF3, a Microviridae phage, which has shown lytic activity against Shigella flexneri, was isolated, purified, and characterized. Morphological and phylogenetic analyses identified it as a phiX174 species belonging to the Microviridae family. The latent period of phage SGF3 was 20 min, with an average burst size of approximately 7.1. Host spectrum experiments indicated its strong host specificity. Furthermore, the biofilm removal efficiency was increased by 20%-25% when SGF3 was coupled with other phages. In conclusion, the phage SGF3 found in this study was a lytic phage belonging to the Microviral family, and could be added as an auxiliary material in the phage cocktail. Studies of its characteristics and bactericidal properties had enriched the germplasm resources of microphages, provided more potential material in fighting against emerging and existing multidrug-resistant bacteria.

Molecular Characteristics of Novel Phage vB_ShiP-A7 Infecting Multidrug-Resistant Shigella flexneri and Escherichia coli, and Its Bactericidal Effect in vitro and in vivo

In recent years, increasing evidence has shown that bacteriophages (phages) can inhibit infection caused by multidrug-resistant (MDR) bacteria. Here, we isolated a new phage, named vB_ShiP-A7, using MDR Shigella flexneri as the host. vB_ShiP-A7 is a novel member of Podoviridae, with a latency period of approximately 35 min and a burst size of approximately 100 phage particles/cell. The adsorption rate constant of phage vB_ShiP-A7 to its host S. flexneri was 1.405 × 10^–8 mL/min. The vB_ShiP-A7 genome is a linear double-stranded DNA composed of 40,058 bp with 177 bp terminal repeats, encoding 43 putative open reading frames. Comparative genomic analysis demonstrated that the genome sequence of vB_ShiP-A7 is closely related to 15 different phages, which can infect different strains. Mass spectrometry analysis revealed that 12 known proteins and 6 hypothetical proteins exist in the particles of phage vB_ShiP-A7. Our results confirmed that the genome of vB_ShiP-A7 is free of lysogen-related genes, bacterial virulence genes, and antibiotic resistance genes. vB_ShiP-A7 can significantly disrupt the growth of some MDR clinical strains of S. flexneri and Escherichia coli in liquid culture and biofilms in vitro. In addition, vB_ShiP-A7 can reduce the load of S. flexneri by approximately 3–10 folds in an infection model of mice. Therefore, vB_ShiP-A7 is a stable novel phage with the potential to treat infections caused by MDR strains of S. flexneri and E. coli.

Activity of the lyases LysSSE1 and HolSSE1 against common pathogenic bacteria and their antimicrobial efficacy in biofilms

Bacillary dysentery is a common foodborne disease with an exaggerated mortality rate because of Shigella infection. With the increasing severity of Shigella infection, lyase has been considered as the most promising alternative to antimicrobial agents, owing to the emergence of resistant bacteria and the difficulty in disrupting and eliminating bacterial biofilms. In this study, we cloned and characterised HolSSE1 and LysSSE1, holin, and lysozyme from the S. dysenteriae phage SSE1 with extended bacterial host range against common gram-negative and gram-positive bacteria. In addition, the efficacy of HolSSE1 and LysSSE1 in removing bacterial biofilms was observed on polystyrene surfaces. Moreover, synergistic bacteriostasis was observed when they were used together. Alignment and structural model analysis showed that both HolSSE1 and LysSSE1 are T4 phage proteins that have not yet been identified. Therefore, HolSSE1 and LysSSE1 can be promising biocontrol agents for the prevention and treatment of various pathogenic infections.

Wastewater as a fertility source for novel bacteriophages against multi-drug resistant bacteria

Antibiotic resistance is a common and serious public health worldwide. As an alternative to antibiotics, bacteriophage (phage) therapy offers one of the best solutions to antibiotic resistance. Bacteriophages survive where their bacterial hosts are found; thus, they exist in almost all environments and their applications are quite varied in the medical, environmental, and industrial fields. Moreover, a single phage or a mixture of phages can be used in phage therapy; mixed phages tend to be more effective in reducing the number and/or activity of pathogenic bacteria than that of a single phage.

Isolation and Characterization of a Novel myovirus Infecting Shigella dysenteriae from the Aeration Tank Water

The genome sequence, morphology, and genetic features of a novel phage, named SSE1, is reported here. Phage SSE1 that infects Shigella dysenteriae (China General Microbiological Culture Collection Center number: 1.1869) was isolated from the aeration tank water of a sewage treatment plant. SSE1 showed morphological features associated with those of phages in Myoviridae. The whole genome sequence of phage SSE1 is composed of 169,744 bp with the GC content of 37.51%. The double-stranded DNA of SSE1 contains 270 open reading frameworks (ORFs). Phylogenetically, phage SSE1 showed a stronger homology (whole genome and terminase large subunit protein sequence) to Escherichia phages than other Shigella phages in the NCBI database, but SSE1 did not infect Escherichia stains. This indicates that phage SSE1 should be a novel phage infecting Shigella dysenteriae. Besides, the result of this study provided a new idea for phage therapy. SSE1 may become a candidate for potential therapy against Shigella dysenteriae infection in clinical applications.