Potential of bacteriophages as disinfectants to control of Staphylococcus aureus biofilms

Isolation and characterisation of a novel Silviavirus bacteriophage promising antimicrobial agent against methicillin-resistant Staphylococcus aureus infections

The increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) emphasises the urgent need for novel antimicrobial agents as alternatives to antibiotics. Bacteriophage therapy is one of the most promising antimicrobial strategies. Here, we isolated and comprehensively characterized a novel Staphylococcus phage, vB_SauM_VL10 (VL10), from urban sewage. The VL10 genome displays 141,746 bp of linear double-stranded DNA, containing 193 open reading frames and lacking tRNA, virulence, or antibiotic resistance genes. Phylogenetic analysis categorizes VL10 as a novel species within the Silviavirus genus, Twortvirinae subfamily. VL10 exhibits lytic behaviour characterized by efficient adsorption, a short latent period, and substantial burst size, with environmental stability. It demonstrates lytic activity against 79.06% of tested S. aureus strains, highlighting its species specificity. Additionally, VL10 effectively targets MRSA biofilms, reducing biomass and viable cells. In MRSA-infected G. mellonella larvae, VL10 enhances survival rates, supporting its potential for phage therapy applications. Moreover, the emergence of VL10-resistant S. aureus strains associated with fitness trade-offs, including reduced growth, biofilm formation, and virulence. Altogether, these findings emphasize VL10 as a promising candidate for developing therapeutic agents against MRSA infections, providing insights into phage biology and resistance dynamics.

Emerging Approaches for Mitigating Biofilm-Formation-Associated Infections in Farm, Wild, and Companion Animals

The importance of addressing the problem of biofilms in farm, wild, and companion animals lies in their pervasive impact on animal health and welfare. Biofilms, as resilient communities of microorganisms, pose a persistent challenge in causing infections and complicating treatment strategies. Recognizing and understanding the importance of mitigating biofilm formation is critical to ensuring the welfare of animals in a variety of settings, from farms to the wild and companion animals. Effectively addressing this issue not only improves the overall health of individual animals, but also contributes to the broader goals of sustainable agriculture, wildlife conservation, and responsible pet ownership. This review examines the current understanding of biofilm formation in animal diseases and elucidates the complex processes involved. Recognizing the limitations of traditional antibiotic treatments, mechanisms of resistance associated with biofilms are explored. The focus is on alternative therapeutic strategies to control biofilm, with illuminating case studies providing valuable context and practical insights. In conclusion, the review highlights the importance of exploring emerging approaches to mitigate biofilm formation in animals. It consolidates existing knowledge, highlights gaps in understanding, and encourages further research to address this critical facet of animal health. The comprehensive perspective provided by this review serves as a foundation for future investigations and interventions to improve the management of biofilm-associated infections in diverse animal populations.

Effective elimination of bacteria on hard surfaces by the combined use of bacteriophages and chemical disinfectants

Hospital-acquired infections (HAIs) represent one of the significant causes of morbidity and mortality worldwide, and controlling pathogens in the hospital environment is of great importance. Currently, the standard disinfection method in the hospital environment is chemical disinfection. However, disinfectants are usually not used strictly according to the label, making them less effective in disinfection. Therefore, there is an emergent need to find a better approach that can be used in hospitals to control pathogenic bacteria in the clinical environment. Bacteriophages (phages) are effective in killing bacteria and have been applied in the treatment of bacterial infections but have not received enough attention regarding the control of contamination in the clinical environment. In this study, we found that various phages remain active in the presence of chemical disinfectants. Moreover, the combined use of specific phages and chemical disinfectants is more effective in removing bacterial biofilms and eliminating bacteria on hard surfaces. Thus, this proof-of-concept study indicates that adding phages directly to chemical disinfectants might be an effective and economical approach to enhance clinical environment disinfection.

IMPORTANCE

In this study, we investigated whether the combination of bacteriophages and chemical disinfectants can enhance the efficacy of reducing bacterial contamination on hard surfaces in the clinical setting. We found that specific phages are active in chemical disinfectants and that the combined use of phages and chemical disinfectants was highly effective in reducing bacterial presence on hard surfaces. As a proof-of-concept, we demonstrated that adding specific phages directly to chemical disinfectants is an effective and cost-efficient strategy for clinical environment disinfection.

The current state of phage therapy in livestock and companion animals

In a global context, bacterial diseases caused by pathogenic bacteria have inflicted sustained damage on both humans and animals. Although antibiotics initially appeared to offer an easy treatment for most bacterial infections, the recent rise of multidrug-resistant bacteria, stemming from antibiotic misuse, has prompted regulatory measures to control antibiotic usage. Consequently, various alternatives to antibiotics are being explored, with a particular focus on bacteriophage (phage) therapy for treating bacterial diseases in animals. Animals are broadly categorized into livestock, closely associated with human dietary habits, and companion animals, which have attracted increasing attention. This study highlights phage therapy cases targeting prominent bacterial strains in various animals. In recent years, research on bacteriophages has gained considerable attention, suggesting a promising avenue for developing alternative substances to antibiotics, particularly crucial for addressing challenging bacterial diseases in the future.

Fighting antibiotic resistance in the local management of bovine mastitis

Bovine mastitis is a widespread infectious disease with a significant economic burden, accounting for 80 % of the antibiotic usage in dairy animals. In recent years, extensive research has focused on using biomimetic approaches such as probiotics, bacteriocins, bacteriophages, or phytochemicals as potential alternatives to antibiotics. The local administration of therapeutic molecules through the intramammary route is one of the most commonly strategies to manage bovine mastitis. This review highlights the most important findings in this field and discusses their local application in mastitis therapy. In contrast to antibiotics, the proposed alternatives are not limited to promote bacterial death but consider other factors associated to the host microenvironments. To this end, the proposed biomimetic strategies can modulate different stages of infection by modifying the local microbiota, preventing oxidative stress, reducing bacterial adhesion to epithelial cells, modulating the immune response, or mediating the inflammatory process. Numerous in vitro studies support the antimicrobial, antibiofilm or antioxidant properties of these alternatives. However, in vivo studies incorporating these components within pharmaceutical formulations with potential clinical application are limited. The development of secure, stable, and effective drug delivery systems based on the proposed options is necessary to achieve real alternatives to antibiotics in the clinic.

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.

Myriad applications of bacteriophages beyond phage therapy

Bacteriophages are the most abundant biological entity on the planet, having pivotal roles in bacterial ecology, animal and plant health, and in the biogeochemical cycles. Although, in principle, phages are simple entities that replicate at the expense of their bacterial hosts, due the importance of bacteria in all aspects of nature, they have the potential to influence and modify diverse processes, either in subtle or profound ways. Traditionally, the main application of bacteriophages is phage therapy, which is their utilization to combat and help to clear bacterial infections, from enteric diseases, to skin infections, chronic infections, sepsis, etc. Nevertheless, phages can also be potentially used for several other tasks, including food preservation, disinfection of surfaces, treatment of several dysbioses, and modulation of microbiomes. Phages may also be used as tools for the treatment of non-bacterial infections and pest control in agriculture; moreover, they can be used to decrease bacterial virulence and antibiotic resistance and even to combat global warming. In this review manuscript we discuss these possible applications and promote their implementation.

Exploring the Benefits of Metal Ions in Phage Cocktail for the Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA) Infection

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is an important zoonotic pathogen worldwide. Infections due to MRSA are associated with higher mortality rates compared with methicillin-susceptible S. aureus. Meanwhile, bacteriophages have been shown to overcome the emergence of MRSA.

Methods

Phage PHB22a, PHB25a, PHB38a, and PHB40a were isolated. Here, we evaluated the ability of a phage cocktail containing phages PHB22a, PHB25a, PHB38a, and PHB40a against MRSA S-18 strain in vivo and in vitro. Phage whole-genome sequencing, host-range determination, lytic activity, and biofilm clearance experiments were performed in vitro. Galleria mellonella larvae and a mouse systemic infection model to evaluate the efficacy of phage therapy in vivo.

Results

The phage cocktail exhibited enhanced antibacterial and anti-biofilm effects compared to the single phage. Phage cocktail contained with Ca²⁺/Zn²⁺ significantly reduced the number of viable bacteria (24-h or 48-h biofilm) by more than 0.81-log compared to the phage cocktail alone. Furthermore, we demonstrated that the addition of Ca²⁺ and Zn²⁺ phage cocktail could increase the survival rate of G. mellonella larvae infected with S. aureus by 10% compared with phage cocktail alone. This was further confirmed in the mouse model, which showed a 2.64-log reduction of host bacteria S-18, when Ca²⁺ and Zn²⁺ were included in the cocktail compared with the phage cocktail alone.

Conclusion

Our results indicated that phage cocktail supplemented with Ca²⁺/Zn²⁺ could effectively remove bacteria in biofilms and mice tissues infected with S. aureus.

Renaissance for Phage-Based Bacterial Control

Bacteriophages (phages) are an underutilized biological resource with vast potential for pathogen control and microbiome editing. Phage research and commercialization have increased rapidly in biomedical and agricultural industries, but adoption has been limited elsewhere. Nevertheless, converging advances in DNA sequencing, bioinformatics, microbial ecology, and synthetic biology are now poised to broaden phage applications beyond pathogen control toward the manipulation of microbial communities for defined functional improvements. Enhancements in sequencing combined with network analysis make it now feasible to identify and disrupt microbial associations to elicit desirable shifts in community structure or function, indirectly modulate species abundance, and target hub or keystone species to achieve broad functional shifts. Sequencing and bioinformatic advancements are also facilitating the use of temperate phages for safe gene delivery applications. Finally, integration of synthetic biology stands to create novel phage chassis and modular genetic components. While some fundamental, regulatory, and commercialization barriers to widespread phage use remain, many major challenges that have impeded the field now have workable solutions. Thus, a new dawn for phage-based (chemical-free) precise biocontrol and microbiome editing is on the horizon to enhance, suppress, or modulate microbial activities important for public health, food security, and more sustainable energy production and water reuse.

Prospects of bacteriophage collections in disinfectant applications

Background and Aim:

The search and development of disinfectants is promising worldwide. However, there are currently no international regulations governing the testing and registration of germicidal agents. Moreover, the number of safety requirements for disinfectants for human, animal, and environmental health has increased. This research aimed to evaluate the prospects of using a collection of bacteriophages for disinfectant purposes.

Materials and Methods:

The objects of research were bacteriophages isolated from a total of 129 environmental samples obtained from seven sources in and around livestock buildings: (1) Feed residues from feeders and automatic drinkers; (2) washouts from floors, walls, and posts; (3) soil from underneath floors; (4) bedding; (5) sewage; (6) ponds; and (7) soil from paddocks. The corresponding strains were used as indicator test cultures for bacteriophages. The authors employed the following methods to work with bacteriophages: (a) Bacteriophage isolation methods, (b) the Appelman method (i.e., serial dilutions), (c) the Grazia method (i.e., agar layers), (d) phage titration on solid media, and (e) the bacterial phagotyping method.

Results:

The results of the analysis on the bacteria of the Enterobacteriaceae family isolated 11 bacteriophages; one bacteriophage is specific to Pseudomonas aeruginosa, and another one is specific to Brucella abortus. The results also indicate that all bacteriophage strains of the Enterobacteriaceae family demonstrate lysis at a pH of 7.0. In addition, this polyphage lyses all strains of sensitive bacterial cultures. The optimum temperature for the cultivation of bacteriophages is 35°C. While using electron microscopy to study the consortium of bacteriophages, clearly distinguishable virions of bacteriophages were found in the microscope field of view.

Conclusion:

The main parameters for the production of polyphages include the ratio of the bacteriophage and its corresponding bacteriophage-sensitive culture, the pH of the cultivation medium, and the cultivation time of the bacteriophage system as well as the sensitive bacterium. With regard to the aforementioned parameters, the results indicate that the average value for all bacteriophages is 1:2, and the average cultivation medium pH is 7.0 for all bacteriophages. The average cultivation time for all bacteriophages is 18-24 h.

Improved bactericidal efficacy and thermostability of Staphylococcus aureus-specific bacteriophage SA3821 by repeated sodium pyrophosphate challenges

As antibiotic resistance is being a threat to public health worldwide, bacteriophages are re-highlighted as alternative antimicrobials to fight with pathogens. Various wild-type phages isolated from diverse sources have been tested, but potential mutant phages generated by genome engineering or random mutagenesis are drawing increasing attention. Here, we applied a chelating agent, sodium pyrophosphate, to the staphylococcal temperate Siphoviridae phage SA3821 to introduce random mutations. Through 30 sequential sodium pyrophosphate challenges and random selections, the suspected mutant phage SA3821^M was isolated. SA3821^M maintained an intact virion morphology, but exhibited better bactericidal activity against its host Staphylococcous aureus CCARM 3821 for up to 17 h and thermostability than its parent, SA3821. Sodium pyrophosphate-mediated mutations in SA3821^M were absent in lysogenic development genes but concentrated (83.9%) in genes related to the phage tail, particularly in the tail tape measure protein, indicating that changes in the tail module might have been responsible for the altered traits. This intentional random mutagenesis through controlled treatments with sodium pyrophosphate could be applied to other phages as a simple but potent method to improve their traits as alternative antimicrobials.

Bacterial Biofilm Destruction: A Focused Review On The Recent Use of Phage-Based Strategies With Other Antibiofilm Agents

Biofilms are bacterial communities that live in association with biotic or abiotic surfaces and enclosed in an extracellular polymeric substance. Their formation on both biotic and abiotic surfaces, including human tissue and medical device surfaces, pose a major threat causing chronic infections. In addition, current antibiotics and antiseptic agents have shown limited ability to completely remove biofilms. In this review, the authors provide an overview on the formation of bacterial biofilms and its characteristics, burden and evolution with phages. Moreover, the most recent possible use of phages and phage-derived enzymes to combat bacteria in biofilm structures is elucidated. From the emerging results, it can be concluded that despite successful use of phages and phage-derived products in destroying biofilms, they are mostly not adequate to eradicate all bacterial cells. Nevertheless, a combined therapy with the use of phages and/or phage-derived products with other antimicrobial agents including antibiotics, nanoparticles, and antimicrobial peptides may be effective approaches to remove biofilms from medical device surfaces and to treat their associated infections in humans.

Bacteriophage treatment before chemical disinfection can enhance removal of plastic surface-associated Pseudomonas aeruginosa

Opportunistic pathogens can linger on surfaces in hospital and building plumbing environments, leading to infections in at-risk populations. Further, biofilm-associated bacteria are protected from removal and inactivation protocols, such as disinfection. Bacteriophages show promise as tools to treat antibiotic resistant infections. As such, phages may also be useful in environmental applications to prevent newly acquired infections. In the current study, the potential of synergies between bacteriophage and chemical disinfection of the opportunistic pathogen Pseudomonas aeruginosa was assessed under various conditions. Specifically, surface-associated P. aeruginosa was treated with various concentrations of phages (P1 or JG004), chemical disinfectant (sodium hypochlorite or benzalkonium chloride), or combined sequential treatments under three distinct attachment models (spot inoculations, dry biofilms, and wet biofilms). Phages were very effective at removing bacteria in spot inoculation (>3.2 log₁₀ removal) and wet biofilms (up to 2.6 log₁₀ removal), while phages prevented regrowth of dry biofilms in the application time. In addition, phage treatment followed by chemical disinfection inactivated more P. aeruginosa under wet biofilm conditions better than either treatment alone. This effect was hindered when chemical disinfection was applied first, followed by phage treatment, suggesting additive benefits of combination treatments are lost when phage is applied last. Further, we confirm prior evidence of greater phage tolerance to benzalkonium chloride relative to sodium hypochlorite, informing choices for combination phage-disinfectant approaches. Overall, this paper further supports the potential of using combination phage and chemical disinfectant treatments to improve inactivation of surface-associated P. aeruginosa. Importance Phages are already utilized in the healthcare industry to treat antibiotic resistant infections, such as on implant-associated biofilms and in compassionate care cases. Phage treatment could also be a promising new tool to control pathogens in the built environment, preventing infections from occurring. This study shows that phage can be combined effectively with chemical disinfectants to improve removal of wet biofilms and bacteria spotted onto surfaces while preventing regrowth in dry biofilms. This has the potential to improve pathogen containment within the built environment and drinking water infrastructure to prevent infections of opportunistic pathogens.