Isolation and evaluation of the efficacy of bacteriophages against multidrug-resistant (MDR), methicillin-resistant (MRSA) and biofilm-producing strains of Staphylococcus aureus recovered from bovine mastitis

Immunomodulation in Non-traditional Therapies for Methicillin-resistant Staphylococcus aureus (MRSA) Management

The rise of methicillin-resistant Staphylococcus aureus (MRSA) poses a significant challenge in clinical settings due to its ability to evade conventional antibiotic treatments. This overview explores the potential of immunomodulatory strategies as alternative therapeutic approaches to combat MRSA infections. Traditional antibiotics are becoming less effective, necessitating innovative solutions that harness the body's immune system to enhance pathogen clearance. Recent advancements in immunotherapy, including the use of antimicrobial peptides, phage therapy, and mechanisms of immune cells, demonstrate promise in enhancing the body's ability to clear MRSA infections. However, the exact interactions between these therapies and immunomodulation are not fully understood, underscoring the need for further research. Hence, this review aims to provide a broad overview of the current understanding of non-traditional therapeutics and their impact on immune responses, which could lead to more effective MRSA treatment strategies. Additionally, combining immunomodulatory agents with existing antibiotics may improve outcomes, particularly for immunocompromised patients or those with chronic infections. As the landscape of antibiotic resistance evolves, the development of effective immunotherapeutic strategies could play a vital role in managing MRSA infections and reducing reliance on traditional antibiotics. Future research must focus on optimizing these approaches and validating their efficacy in diverse clinical populations to address the urgent need for effective MRSA management strategies.

Prevalence and Phage-Based Biocontrol of Methicillin-Resistant Staphylococcus aureus Isolated from Raw Milk of Cows with Subclinical Mastitis in Vietnam

S. aureus, particularly methicillin-resistant S. aureus, has been recognized as a main cause of bovine mastitis and food poisoning. This study investigated the prevalence, antibiotic resistance, and phage-based biocontrol of S. aureus and methicillin-resistant S. aureus isolated from raw milk of cows with subclinical mastitis. The results showed that the prevalence of S. aureus and methicillin-resistant S. aureus was 12% (48/400) and 1.5% (6/400), respectively. The S. aureus isolates were highly resistant to penicillin (72.92%), erythromycin (43.75%), and tetracycline (39.58%). Out of 48 S. aureus isolates, 6 were identified as methicillin-resistant strains. Among them, one isolate was found to harbor the sea gene. A total of 5 phages were recovered from 50 pork and 50 chicken meat samples, 1 from pork and 4 from chicken meat samples. Phage PSA2 capable of lysing all 6 methicillin-resistant isolates was selected for characterization. The use of phage PSA2 completely inactivated methicillin-resistant S. aureus SA33 in raw milk at both 24 °C and 4 °C, indicating its potential as a promising antibacterial agent in controlling methicillin-resistant S. aureus in raw milk and treating bovine mastitis.

When the solution becomes the problem: a review on antimicrobial resistance in dairy cattle

Antibiotics' action, once a 'magic bullet', is now hindered by widespread microbial resistance, creating a global antimicrobial resistance (AMR) crisis. A primary driver of AMR is the selective pressure from antimicrobial use. Between 2000 and 2015, antibiotic consumption increased by 65%, reaching 34.8 billion tons, 73% of which was used in animals. In the dairy cattle sector, antibiotics are crucial for treating diseases like mastitis, posing risks to humans, animals and potentially leading to environmental contamination. To address AMR, strategies like selective dry cow therapy, alternative treatments (nanoparticles, phages) and waste management innovations are emerging. However, most solutions are in development, emphasizing the urgent need for further research to tackle AMR in dairy farms.

A simplified method of bacteriophage preparation for transmission electron microscope

Bacteriophages are viruses that infect bacteria. Researchers use different methods to study the characteristics of bacteriophages. Transmission electron microscope (TEM) is considered the best method to analyze these characteristics. However, the quality of TEM micrographs is significantly influenced by the preparation methods used to prepare the bacteriophages sample. In this study, researchers compared two different methods for preparing the bacteriophage samples. In one method was used SM buffer, while in the other used deionized water. The results were analyzed by TEM and compared with each other. Additionally, the viability of bacteriophage in deionized water and SM buffer at 4°C was determined through plaque assay within 72 hours. TEM micrographs showed that the quality of bacteriophage sample prepared with deionized water is superior to those prepared with SM buffer. Furthermore, the titer of the bacteriophages did not show a significant reduction during 72 hours in both SM and deionized water. In conclusion, the results suggested that preparation method can significantly impact the quality of TEM micrographs. Using sterile deionized water for the preparation of bacteriophages is a simple way to improve the quality of TEM micrographs and it is advisable to send the samples to the laboratory within 72 hours.

Bacteriophages for Controlling Staphylococcus spp. Pathogens on Dairy Cattle Farms: In Vitro Assessment

Pathogenic Staphylococcus spp. strains are significant agents involved in mastitis and in skin and limb infections in dairy cattle. The aim of this study was to assess the antibacterial effectiveness of bacteriophages isolated from dairy cattle housing as potential tools for maintaining environmental homeostasis. The research will contribute to the use of phages as alternatives to antibiotics. The material was 56 samples obtained from dairy cows with signs of limb and hoof injuries. Staphylococcus species were identified by phenotypic, MALDI-TOF MS and PCR methods. Antibiotic resistance was determined by the disc diffusion method. Phages were isolated from cattle housing systems. Phage activity (plaque forming units, PFU/mL) was determined on double-layer agar plates. Morphology was examined using TEM microscopy, and molecular characteristics were determined with PCR. Among 52 strains of Staphylococcus spp., 16 were used as hosts for bacteriophages. Nearly all isolates (94%, 15/16) showed resistance to neomycin, and 87% were resistant to spectinomycin. Cefuroxime and vancomycin were the most effective antibiotics. On the basis of their morphology, bacteriophages were identified as class Caudoviricetes, formerly Caudovirales, families Myoviridae-like (6), and Siphoviridae-like (9). Three bacteriophages of the family Myoviridae-like, with the broadest spectrum of activity, were used for further analysis. This study showed a wide spectrum of activity against the Staphylococcus spp. strains tested. The positive results indicate that bacteriophages can be used to improve the welfare of cattle.

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 entrapped chitosan microgel for the treatment of biofilm-mediated polybacterial infection in burn wounds

Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria are most commonly present in burn wound infections. Multidrug resistance (MDR) and biofilm formation make it difficult to treat these infections. Bacteriophages (BPs) are proven as an effective therapy against MDR as well as biofilm-associated wound infections. In the present work, a naturally inspired bacteriophage cocktail loaded chitosan microparticles-laden topical gel has been developed for the effective treatment of these infections. Bacteriophages against MDR S. aureus (BPSAФ1) and P. aeruginosa (BPPAФ1) were isolated and loaded separately and in combination into the chitosan microparticles (BPSAФ1-CHMPs, BPPAФ1-CHMPs, and MBP-CHMPs), which were later incorporated into the SEPINEO™ P 600 gel (BPSAФ1-CHMPs-gel, BPPAФ1-CHMPs-gel, and MBP-CHMPs-gel). BPs were characterized for their morphology, lytic activity, burst size, and hemocompatibility, and BPs belongs to Caudoviricetes class. Furthermore, BPSAФ1-CHMPs, BPPAФ1-CHMPs, and MBP-CHMPs had an average particle size of 1.19 ± 0.11, 1.42 ± 0.21, and 2.84 ± 0.28 μm, respectively, and expressed promising in vitro antibiofilm eradication potency. The ultrasound and photoacoustic imaging in infected burn wounds demonstrated improved wound healing reduced inflammation and increased oxygen saturation following treatment with BPs formulations. The obtained results suggested that the incorporation of the BPs in the MP-gel protected the BPs, sustained the BPs release, and improved the antibacterial activity.

A Bacteriophage-Loaded Microparticle Laden Topical Gel for the Treatment of Multidrug-Resistant Biofilm-Mediated Burn Wound Infection

Klebsiella pneumoniae is regarded as one of the most profound bacteria isolated from the debilitating injuries caused by burn wounds. In addition, the multidrug resistance (MDR) and biofilm formation make treating burn patients with clinically available antibiotics difficult. Bacteriophage therapy has been proven an effective alternative against biofilm-mediated wound infections caused by MDR bacterial strains. In the current study, the bacteriophage (BPKPФ1) against MDR Klebsiella pneumoniae was isolated and loaded into the chitosan microparticles (CHMPs), which was later incorporated into the Sepineo P 600 to convert into a gel (BPKPФ1-CHMP-gel). BPKPФ1 was characterized for lytic profile, morphological class, and burst size, which revealed that the BPKPФ1 belongs to the family Siphoviridae. Moreover, BPKPФ1 exhibited a narrow host range with 128 PFU/host cell of burst size. The BPKPФ1-loaded CHMPs showed an average particle size of  1.96 ± 0.51 μm, zeta potential 32.16 ± 0.41 mV, and entrapment efficiency in the range of 82.44 ± 1.31%. Further, the in vitro antibacterial and antibiofilm effectiveness of BPKPФ1-CHMPs-gel were examined. The in vivo potential of the BPKPФ1-CHMPs-gel was assessed using a rat model with MDR Klebsiella pneumoniae infected burn wound, which exhibited improved wound contraction (89.22 ± 0.48%) in 28 days with reduced inflammation, in comparison with different controls. Data in hand suggest the potential of bacteriophage therapy to be developed as personalized therapy in case of difficult-to-treat bacterial infections.

Alternatives to antibiotics for treatment of mastitis in dairy cows

Mastitis is considered the costliest disease on dairy farms and also adversely affects animal welfare. As treatment (and to a lesser extent prevention) of mastitis rely heavily on antibiotics, there are increasing concerns in veterinary and human medicine regarding development of antimicrobial resistance. Furthermore, with genes conferring resistance being capable of transfer to heterologous strains, reducing resistance in strains of animal origin should have positive impacts on humans. This article briefly reviews potential roles of non-steroidal anti-inflammatory drugs (NSAIDs), herbal medicines, antimicrobial peptides (AMPs), bacteriophages and their lytic enzymes, vaccination and other emerging therapies for prevention and treatment of mastitis in dairy cows. Although many of these approaches currently lack proven therapeutic efficacy, at least some may gradually replace antibiotics, especially as drug-resistant bacteria are proliferating globally.