Bacteriophages and phage products: Applications in medicine and biotechnological industries, and general concerns

Bacteriophage therapy: a possible alternative therapy against antibiotic-resistant strains of Klebsiella pneumoniae

Klebsiella pneumoniae is a notorious, Gram-negative pathogen and is a leading cause of healthcare settings and community-acquired infections. This is the commensal of human microbiota and can invade and cause infections in different body parts. The global emergence of antibiotic resistance in K. pneumoniae has become a major challenge in the whole medical community. Alternative paths to treat the infections caused by these MDR pathogens are needed as these bacteria become resistant to last-resort antibiotics like colistin. The lytic bacteriophages (phages) are the bacteria's natural predators and can rapidly eliminate the bacterial cells. Phages are abundant in nature and have recently been found to be effective tools in modern biotechnology. They can be used to control the bacterial infectious diseases. They can be manipulated easily and potentially used in therapeutics, biotechnology, and research. Several studies, both in vitro and in vivo, have demonstrated the possible applications of the lytic phages in treating K. pneumoniae superbug strains. Phage endolysins have drawn the scientific world's attention because of their involvement in phage adsorption and bacterial capsules digestion. These phage-encoded enzymes digest the polysaccharide components of bacterial cell walls by recognizing and binding them. Phage lysins, being strong biological agents, are capable of effectively and swiftly eliminating bacteria. This review summarizes the information on phages of K. pneumoniae and phage-based therapies to target their bacterial hosts.

A game of resistance: War between bacteria and phages and how phage cocktails can be the solution

While phages hold promise as an antibiotic alternative, they encounter significant challenges in combating bacterial infections, primarily due to the emergence of phage-resistant bacteria. Bacterial defence mechanisms like superinfection exclusion, CRISPR, and restriction-modification systems can hinder phage effectiveness. Innovative strategies, such as combining different phages into cocktails, have been explored to address these challenges. This review delves into these defence mechanisms and their impact at each stage of the infection cycle, their challenges, and the strategies phages have developed to counteract them. Additionally, we examine the role of phage cocktails in the evolving landscape of antibacterial treatments and discuss recent studies that highlight the effectiveness of diverse phage cocktails in targeting essential bacterial receptors and combating resistant strains.

Effect of Bacteriophages against Biofilms of Escherichia coli on Food Processing Surfaces

The bacterial adhesion to food processing surfaces is a threat to human health, as these surfaces can serve as reservoirs of pathogenic bacteria. Escherichia coli is an easily biofilm-forming bacterium involved in surface contamination that can lead to the cross-contamination of food. Despite the application of disinfection protocols, contamination through food processing surfaces continues to occur. Hence, new, effective, and sustainable alternative approaches are needed. Bacteriophages (or simply phages), viruses that only infect bacteria, have proven to be effective in reducing biofilms. Here, phage phT4A was applied to prevent and reduce E. coli biofilm on plastic and stainless steel surfaces at 25 °C. The biofilm formation capacity of phage-resistant and sensitive bacteria, after treatment, was also evaluated. The inactivation effectiveness of phage phT4A was surface-dependent, showing higher inactivation on plastic surfaces. Maximum reductions in E. coli biofilm of 5.5 and 4.0 log colony-forming units (CFU)/cm2 after 6 h of incubation on plastic and stainless steel, respectively, were observed. In the prevention assays, phage prevented biofilm formation in 3.2 log CFU/cm2 after 12 h. Although the emergence of phage-resistant bacteria has been observed during phage treatment, phage-resistant bacteria had a lower biofilm formation capacity compared to phage-sensitive bacteria. Overall, the results suggest that phages may have applicability as surface disinfectants against pathogenic bacteria, but further studies are needed to validate these findings using phT4A under different environmental conditions and on different materials.

Advancements in the Use of Bacteriophages to Combat the Kiwifruit Canker Phytopathogen Pseudomonas syringae pv. actinidiae

Over the last several decades, kiwifruit production has been severely damaged by the bacterial plant pathogen Pseudomonas syringae pv. actinidiae (Psa), resulting in severe economic losses worldwide. Currently, copper bactericides and antibiotics are the main tools used to control this bacterial disease. However, their use is becoming increasingly ineffective due to the emergence of antibiotic resistance. In addition, environmental issues and the changes in the composition of soil bacterial communities are also concerning when using these substances. Although biocontrol methods have shown promising antibacterial effects on Psa infection under in vitro conditions, the efficiency of antagonistic bacteria and fungi when deployed under field conditions remains unclear. Therefore, it is crucial to develop a phage-based biocontrol strategy for this bacterial pathogen. Due to the specificity of the target bacteria and for the benefit of the environment, bacteriophages (phages) have been widely regarded as promising biological agents to control plant, animal, and human bacterial diseases. An increasing number of studies focus on the use of phages for the control of plant diseases, including the kiwifruit bacterial canker. In this review, we first introduce the characteristics of the Psa-induced kiwifruit canker, followed by a description of the diversity and virulence of Psa strains. The main focus of the review is the description of recent advances in the isolation of Psa phages and their characterization, including morphology, host range, lytic activity, genome characterization, and lysis mechanism, but we also describe the biocontrol strategies together with potential challenges introduced by abiotic factors, such as high temperature, extreme pH, and UV irradiation in kiwifruit orchards. The information presented in this review highlights the potential role of phages in controlling Psa infection to ensure plant protection.

Isolation and Partial Characterization of Salmonella Gallinarum Bacteriophage

Infections caused by Salmonella remain a major public health problem worldwide. Animal food products, including poultry meat and eggs, are considered essential components in the individual’s daily nutrition. However, chicken continues to be the main reservoir for Salmonella spp.

Poultry farmers use several types of antibiotics to treat pathogens. This can pose a health risk as pathogens can build antibiotic resistance in addition to the possibility of accumulation of these antibiotics in food products. The use of phages in treating poultry pathogens is increasing worldwide due to its potential use as an effective alternative to antibiotics. Phages have several advantages over antibiotics; phages are very specific to target bacteria, less chances of developing secondary infections, and they only replicate at the site of infection.

Here we report the isolation of a bacteriophage from chicken feces. The isolated bacteriophage hosts on Salmonella Gallinarum, a common zoonotic infection that causes fowl typhoid, known to cause major losses to poultry sector. The isolated bacteriophage was partially characterized as a DNA virus resistant to RNase digestion with approximately 20 Kb genome. SDS-PAGE analysis of total viral proteins showed at least five major bands (21, 28, 42, 55 and 68 kDa), indicating that this virus is relatively small compared to other known poultry phages. The isolated bacteriophage has the potential to be an alternative to antibiotics and possibly reducing antibiotic resistance in poultry farms.

Bacteriophages in the Control of Aeromonas sp. in Aquaculture Systems: An Integrative View

Aeromonas species often cause disease in farmed fish and are responsible for causing significant economic losses worldwide. Although vaccination is the ideal method to prevent infectious diseases, there are still very few vaccines commercially available in the aquaculture field. Currently, aquaculture production relies heavily on antibiotics, contributing to the global issue of the emergence of antimicrobial-resistant bacteria and resistance genes. Therefore, it is essential to develop effective alternatives to antibiotics to reduce their use in aquaculture systems. Bacteriophage (or phage) therapy is a promising approach to control pathogenic bacteria in farmed fish that requires a heavy understanding of certain factors such as the selection of phages, the multiplicity of infection that produces the best bacterial inactivation, bacterial resistance, safety, the host’s immune response, administration route, phage stability and influence. This review focuses on the need to advance phage therapy research in aquaculture, its efficiency as an antimicrobial strategy and the critical aspects to successfully apply this therapy to control Aeromonas infection in fish.

Kiwifruit bacterial canker: an integrative view focused on biocontrol strategies

Phage-based biocontrol strategies can be an effective alternative to control Psa-induced bacterial canker of kiwifruit. The global production of kiwifruit has been seriously affected by Pseudomonas syringae pv. actinidiae (Psa) over the last decade. Psa damages both Actinidia chinensis var. deliciosa (green kiwifruit) but specially the susceptible Actinidia chinensis var. chinensis (gold kiwifruit), resulting in severe economic losses. Treatments for Psa infections currently available are scarce, involving frequent spraying of the kiwifruit plant orchards with copper products. However, copper products should be avoided since they are highly toxic and lead to the development of bacterial resistance to this metal. Antibiotics are also used in some countries, but bacterial resistance to antibiotics is a serious worldwide problem. Therefore, it is essential to develop new approaches for sustainable agriculture production, avoiding the emergence of resistant Psa bacterial strains. Attempts to develop and establish highly accurate approaches to combat and prevent the occurrence of bacterial canker in kiwifruit plants are currently under study, using specific viruses of bacteria (bacteriophages, or phages) to eliminate the Psa. This review discusses the characteristics of Psa-induced kiwifruit canker, Psa transmission pathways, prevention and control, phage-based biocontrol strategies as a new approach to control Psa in kiwifruit orchards and its advantages over other therapies, together with potential ways to bypass phage inactivation by abiotic factors.

Essential Oils: An Impending Substitute of Synthetic Antimicrobial Agents to Overcome Antimicrobial Resistance

Antimicrobial resistance (AMR) is an emerging problem in the world that has a significant impact on our society. AMR made conventional drugs futile against microorganisms and diseases untreatable. Plant-derived medicines are considered to be safe alternatives as compared to synthetic drugs. Active ingredients and the mixtures of these natural medicines have been used for centuries, due to their easy availability, low cost, and negligible side effects. Essential oils (EOs) are the secondary metabolites that are produced by aromatic plants to protect them from microorganisms. However, these EOs and their constituents have shown good fighting potential against drug-resistant pathogens. These oils have been proved extremely effective antimicrobial agents in comparison to antibiotics. Also, the combination of synthetic drugs with EOs or their components improve their efficacy. So, EOs can be established as an alternative to synthetic antimicrobial agents to eradicate tough form of infectious microorganisms. EO's can interact with multiple target sites, like the destruction of cytoplasm membrane or inhibition of protein synthesis and efflux pump, etc. The purpose of this review is to provide information about the antimicrobial activity of EOs attained from different plants, their combination with synthetic antimicrobials. In addition, mechanism of antimicrobial activity of several EOs and their constituents was reported.