Anisotropic Silver Nanoparticles Gel Exhibits Antibacterial Action and Reduced Scar Formation on Wounds Contaminated with Methicillin-Resistant Staphylococcus pseudintermedius (MRSP) in a Mice Model

Methicillin-resistant Staphylococcus pseudintermedius: epidemiological changes, antibiotic resistance, and alternative therapeutic strategies

Staphylococcus pseudintermedius is a major opportunistic bacterial pathogen that belongs to the skin and mucosal microbiota of the dog. Since its global emergence around 2006, multidrug - methicillin-resistant S. pseudintermedius (MRSP) clones have become endemic worldwide. MRSP strains pose a significant threat to animal health and make antimicrobial therapy difficult due to their typical multidrug resistance phenotypes. The difficulty to treat MRSP infections using the current antimicrobials licensed for veterinary use has intensified research efforts to develop new treatment strategies and alternative anti-infective approaches to conventional antimicrobial therapy. The present narrative review outlines the latest changes in the epidemiology of MRSP with focus on the geographical distribution variability and antimicrobial resistance profiles in the main MRSP lineages. It also provides an overview of the effectiveness of currently available antimicrobials and the status of anti-infective alternatives to conventional antimicrobials.Recent studies have reported notable changes in the population structure of MRSP, with the emergence of new epidemic lineages, such as ST258, ST123, ST496, and ST551 in European countries and ST45, ST181, ST258, ST496 in non-European countries, which partly or totally replaced those that were initially prevalent, such as ST71 in Europe and ST68 in the US. Due to methicillin resistance often associated with the resistance to a broader number of antimicrobials, treating canine MRSP skin infection is challenging. Several alternative or supplementary treatment options to conventional antibiotics, especially for topical treatment, such as a novel water-soluble hydroxypyridinone-containing iron-chelating 9 kDa polymer (DIBI), antimicrobial peptides (AMPs), nanoparticles, and bacteriophages seem to be particularly interesting from a clinical perspective.

Antimicrobial Strategies Proposed for the Treatment of S. pseudintermedius and Other Dermato-Pathogenic Staphylococcus spp. in Companion Animals: A Narrative Review

The treatment of dermato-pathogenic Staphylococcus spp., particularly Staphylococcus pseudintermedius, in companion animals presents significant challenges due to rising antimicrobial resistance. This review explores innovative strategies to combat these infections. We examined novel antimicrobials and the repurposing of existing drugs to enhance their efficacy against resistant strains. Additionally, we evaluate the potential of natural products, nanomaterials, and skin antiseptics as alternative treatments. The review also investigates the use of antimicrobial peptides and bacteriophages, highlighting their targeted action against staphylococcal pathogens. Furthermore, the role of adjuvants in antibiotic treatments, such as antimicrobial resistance breakers, is discussed, emphasizing their ability to enhance therapeutic outcomes. Our analysis underscores the importance of a multifaceted approach in developing effective antimicrobial strategies for companion animals, aiming to mitigate resistance and improve clinical management of staphylococcal skin infections.

Superior In Vivo Wound-Healing Activity of Biosynthesized Silver Nanoparticles with Nepeta cataria (Catnip) on Excision Wound Model in Rat

Silver nanoparticles were biosynthesized with Nepeta cataria plant extract. It was determined that the synthesized Nc-AgNPs gave a strong absorbance peak at 438 nm wavelength in the UV-vis spectrophotometer. SEM and TEM analyses of Nc-AgNPs showed that the synthesized nanoparticles had a spherical morphology. Based on XRD analysis, the average crystallite size of Nc-AgNPs was calculated at 15.74 nm. At the same time, EDS spectrum analysis exhibited dominant emission energy at 3 keV, indicative of Nc-AgNPs. Nc-AgNPs showed an inhibition zone of 12 nm in gram-negative Escherichia coli, 10 nm in gram-positive Enterococcus faecalis, and 11 nm in Staphylococcus aureus. Nc-AgNPs showed high antioxidant properties, with 63% at 5000 μg/mL. The wound-healing properties of Nc-AgNPs were evaluated in vivo in wound models created in a total of 20 Wistar albino male rats, divided into four groups. After 10 days of treatment, the highest wound closure rate was seen in the Nc-AgNP + Vaseline (Group IV) treatment group, at 94%. It was observed that Nc-AgNP + Vaseline nanoformulation significantly increased wound healing, similar to Silverdin®, and Vaseline alone supported healing but did not result in complete closure. Histopathological examination revealed an increase in mature Type 1 collagen in Group IV and positive control (Group II), with better collagen maturation in vehicle control (Group III) compared to negative control (Group I). Immunohistochemical analysis showed complete epithelialization in Group IV and Group II, with distinct cytokeratin expressions, while Group III exhibited mild expressions.

Cross-linked chitosan/lysozyme hydrogels with inherent antibacterial activity and tuneable drug release properties for cutaneous drug administration

Gels with high drug release sustainability and intrinsic antibacterial properties are of high practical potential for cutaneous drug administration, particularly for wound care and skin disease treatment. This study reports the generation and characterization of gels formed by 1,5-pentanedial-mediated crosslinking between chitosan and lysozyme for cutaneous drug delivery. Structures of the gels are characterized by using scanning electron microscopy, X-ray diffractometry and Fourier-transform infrared spectroscopy. An increase in the mass percentage of lysozyme leads to an increase in the swelling ratio and erosion susceptibility of the resulting gels. The drug delivery performance of the gels can be changed simply by manipulating the chitosan/lysozyme mass-to-mass ratio, with an increase in the mass percentage of lysozyme leading to a decline in the encapsulation efficiency and drug release sustainability of the gels. Not only do all gels tested in this study show negligible toxicity in NIH/3T3 fibroblasts, they also demonstrate intrinsic antibacterial effects against both Gram-negative and Gram-positive bacteria, with the magnitude of the effect being positively related to the mass percentage of lysozyme. All these warrant the gels to be further developed as intrinsically antibacterial carriers for cutaneous drug administration.

Silver nanoparticles enhance the efficacy of aminoglycosides against antibiotic-resistant bacteria

As the threat of antimicrobial-resistant bacteria compromises the safety and efficacy of modern healthcare practices, the search for effective treatments is more urgent than ever. For centuries, silver (Ag) has been known to have antibacterial properties and, over the past two decades, Ag-based nanoparticles have gained traction as potential antimicrobials. The antibacterial efficacy of Ag varies with structure, size, and concentration. In the present study, we examined Ag nanoparticles (AgNPs) for their antimicrobial activity and safety. We compared different commercially-available AgNPs against gram-negative Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and gram-positive Staphylococcus aureus methicillin-resistant and susceptible strains. The most effective formula of AgNPs tested had single-digit (μg/mL) minimum inhibitory concentrations against gram-negative multidrug-resistant clinical bacterial isolates with novel and emerging mechanisms of resistance. The mode of killing was assessed in E. coli and was found to be bactericidal, which is consistent with previous studies using other AgNP formulations. We evaluated cytotoxicity by measuring physiological readouts using the Caenorhabditis elegans model and found that motility was affected, but not the lifespan. Furthermore, we found that at their antibacterial concentrations, AgNPs were non-cytotoxic to any of the mammalian cell lines tested, including macrophages, stem cells, and epithelial cells. More interestingly, our experiments revealed synergy with clinically relevant antibiotics. We found that a non-toxic and non-effective concentration of AgNPs reduced the minimum inhibitory concentrations of aminoglycoside by approximately 22-fold. Because both aminoglycosides and Ag are known to target the bacterial ribosome, we tested whether Ag could also target eukaryotic ribosomes. We measured the rate of mistranslation at bactericidal concentration and found no effect, indicating that AgNPs are not proteotoxic to the host at the tested concentrations. Collectively, our results suggest that AgNPs could have a promising clinical application as a potential stand-alone therapy or antibiotic adjuvants.

Comparison of antimicrobial and wound-healing effects of silver nanoparticle and chlorhexidine mouthwashes: an in vivo study in rabbits

The objective is to formulate a silver nanoparticle mouthwash and then evaluate its antimicrobial and wound-healing effects in rabbit animal models. Microbial samples were collected from the oral cavity of 60 rabbits. Thereafter, standardized wounds were created in the lateral border of the tongue on the right side for all rabbits. After surgery, digital photographs were obtained from the wounds with standardized settings. To characterize the silver nanoparticles used in the synthetic mouthwash, transmission electron microscopy (TEM) and digital light scattering analysis were used. The animal models were then randomly divided into 4 groups: group 1 received 9.80 wt% silver nanoparticle mouthwash; group 2 received all the ingredients of the formulated mouthwash except for silver nanoparticles; group 3 received chlorhexidine 2.0% mouthwash; and the negative control group did not receive any postoperative mouthwash. Microbial samples were collected from oral cavity of the rabbits each day for four postoperative days. Colony-forming unit (CFU) counts were compared post-operatively with the pre-operative counts. In addition, standardized digital photographs were taken each day from the wounds and the area of the wounds was compared in postoperative and pre-operative images. Data were statistically analyzed using one-way ANOVA and repeated measures variance analysis (α = 0.05). TEM revealed spherical morphology of silver nanoparticles and digital light scattering showed an average size of 5 nm and optimal distribution of the nanoparticles. CFU count significantly decreased in groups 1 and 3 (P < 0.001), while it significantly increased in groups 2 and 4 (P < 0.001). Moreover, a significant difference was observed between the experimental groups (P < 0.001). In addition, wound area decreased significantly in all groups (P < 0.001). However, the difference between wound areas in the groups was not significant, except for the 4th postoperative day (P < 0.001). However, the antibacterial effects and the wound-healing characteristics of the synthetic silver nanoparticle and chlorhexidine mouthwashes were not significantly different (P > 0.05). Silver nanoparticle mouthwash possesses favorable antibacterial and wound-healing effects. The formulated 9.80 wt% silver nanoparticle mouthwash with a particle size of 5 nm can be a promising alternative for application after oral surgical procedures.