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Staphylococcus pseudintermedius is an opportunistic pathogen commonly found in canines, and has garnered escalating interest due to its potential for zoonotic transmission and increasing antimicrobial resistance. However, the excessive use of antibiotics and the characteristic of S. pseudintermedius forming biofilms make treatment challenging. In this study, the in vivo and in vitro antimicrobial activity and mechanisms of action of NZ2114, a plectasin-derived peptide, against S. pseudintermedius were investigated. NZ2114 exhibited potent antibacterial activity towards S. pseudintermedius (minimum inhibitory concentration, MIC = 0.23 μM) with a lower probability of inducing drug-resistant mutations and efficient bactericidal action, which was superior to those of mopirucin (MIC = 0.25–0.5 μM) and lincomycin (MIC = 4.34–69.41 μM). The results of electron microscopy and flow cytometry showed that NZ2114 disrupted S. pseudintermedius' cell membrane, resulting in cellular content leakage, cytoplasmic membrane shrinkage, and, eventually, cell death. The intracellular ROS activity and Alamar Blue detection showed that NZ2114 interferes with intracellular metabolic processes. In addition, NZ2114 effectively inhibits biofilm formation, and confocal laser scanning microscopy further revealed its antibacterial and anti-biofilm activity (biofilm thickness reduced to 6.90–17.70 μm). The in vivo therapy of NZ2114 in a mouse pyoderma model showed that it was better than lincomycin in effectively decreasing the number of skin bacteria, alleviating histological damage, and reducing the skin damage area. These results demonstrated that NZ2114 may be a promising antibacterial candidate against S. pseudintermedius infections. [ABSTRACT FROM AUTHOR]

Staphylococcus pseudintermedius (S. pseudintermedius) is the main pathogen causing pyoderma of canines. With the emergence of drug-resistant bacteria, traditional antibiotic treatments are limited. As a potential antibacterial agent, NZ2114 was effective against S. pseudintermedius, including drug-resistant strains. Its bactericidal efficacy was superior to mupiroxacin, ofloxacin and lincomycin. To facilitate the transcutaneous delivery of NZ2114 for the treatment of superficial pyoderma, chemical permeation enhancers were added since water-soluble NZ2114 does not easily penetrate the skin lipid layer. Two different NZ2114 sprays were prepared by combining 1% Azone + 10% propylene glycol (PG) or 5% N-methylpyrrolidone (NMP) + 10% PG with NZ2114 after screening. The cumulative permeability of NZ2114 sprays were 244.149 and 405.245 μg/cm2 at 24 h with an in vitro percutaneous assay of mice skin, which showed a 244% and 405% increase in skin permeability than NZ2114, respectively. In addition, the efficacy of NZ2114 sprays in reducing skin bacteria colonisation was demonstrated in a mouse model of superficial pyoderma (24 mice, 3 mice/group) induced by S. pseudintermedius, and the 5% NMP + 10% PG + NZ2114 group had the best therapeutic effect compared to the other groups. This preparation did not cause any skin irritation, laying the foundation for the development of an effective and non-toxic topical product. [ABSTRACT FROM AUTHOR]

In the present study, we aimed to investigate the antibacterial activity and mechanisms of plectasin-derived peptide NZ2114 in vitro and its therapeutic effects in vivo on broilers challenged with Clostridium perfringens. In vitro assay showed that NZ2114 had potent (minimal inhibitory concentration, 0.91 μM) and rapid antibacterial activity (99.9% reduction within 2 h), and the dual antibacterial mechanisms (including interfering with the cell membrane and intracellular DNA) against C. perfringens CVCC 2030. In vivo study, NZ2114 tended to increase linearly and quadratically the average daily gain as NZ2114 level increased and was the highest at 20 mg/L. NZ2114 at 10 ~ 40 mg/L dramatically reduced jejunal lesion score. Besides, the levels of IL-6, TNF-α, and IL-1β tended to downregulate linearly and quadratically as the NZ2114 level increased and were all the lowest at the dose of 20 mg/L. NZ2114 significantly upregulated those levels of IgA, IgG, IgM, and sIgA with a linear and quadratic dose effect, with the highest IgA, IgG, IgM, and sIgA at 20 mg/L. Finally, NZ2114 tended to linearly and quadratically increase the numerical value of crypt depth, with the lowest value at 40 mg/L. Lincomycin only dramatically reduced the jejunal lesion score and increased the numerical value of crypt depth. These results indicate that NZ2114 has the potential as a new alternative to antibiotics for the treatment of C. perfringens–induced necrotic enteritis infection. Key points • NZ2114 could kill C. perfringens by dual antibacterial mechanisms • Broiler necrotic enteritis model induced by C. perfringens was established • NZ2114 treatment could ameliorate C. perfringens–induced necrotic enteritis [ABSTRACT FROM AUTHOR]

Streptococcosis is recognized as a leading infectious disease in the swine industry. Streptococcus suis serotype 2 is regarded as the most virulent species, which threatens human and pig health and causes serious economic losses. In this study, multiple in vitro and in vivo effects of MP1102 on multidrug resistant S. suis was studied for the first time. MP1102 exhibited significant antibacterial activity against S. suis (minimum inhibitory concentration, MIC = 0.028–0.228 μM), rapid bacteriocidal action, a longer postantibiotic effect than ceftriaxone, and a synergistic or additive effect with lincomycin, penicillin, and ceftriaxone (FICI = 0.29–0.96). No resistant mutants appeared after 30 serial passages of S. suis in the presence of MP1102. Flow cytometric analysis and electron microscopy observations showed that MP1102 destroyed S. suis cell membrane integrity and affected S. suis cell ultrastructure and membrane morphology. Specifically, a significantly wrinkled surface, intracellular content leakage, and cell lysis were noted, establishing a cyto-basis of nonresistance to this pathogen. DNA gel retardation and circular dichroism analysis indicated that MP1102 interacted with DNA by binding to DNA and changing the DNA conformation, even leading to the disappearance of the helical structure. This result further supported the mechanistic basis of nonresistance via interaction with an intracellular target, which could serve as a means of secondary injury after MP1102 is transported across the membrane. Upon treatment with 2.5–5.0 mg/kg MP1102, the survival of mice challenged with S. suis was 83.3–100%. MP1102 decreased bacterial translocation in liver, lung, spleen, and blood; inhibited the release of interleukin-1β and tumor necrosis factor-α; and relieved the lung, liver, and spleen from acute injury induced by S. suis. These results suggest that MP1102 is a potent novel antibacterial agent for the treatment of porcine streptococcal disease. [ABSTRACT FROM AUTHOR]

NZ2114 is a promising candidate for therapeutic application owing to potent activity to gram-positive bacterium such as Streptococcus pneumoniae and Staphylococcus aureus. This work is the first report to describe the in vitro and in vivo antibacterial characteristics of NZ2114 against Streptococcus suis. It exhibited strong antimicrobial activity against S. suis type 2 strains CVCC 606, CVCC 3309, and CVCC 3928 at a low minimal inhibitory concentration (MIC) of 0.03-0.06 μM. The NZ2114 killed over 99.9% of tested S. suis CVCC 606 in Mueller-Hinton medium within 4 h when treated with 4 × MIC. It caused only less than 0.25% hemolytic activity in the concentration of 256 μg/ml. Additionally, NZ2114 exhibited potent in vivo activity to S. suis. All mice were survival when the dosage was low to 0.2 mg/kg. Over 99% of S. suis cells were killed within 4 h in blood, lung, liver and spleen with dosage of 10, 20, and 40 mg/kg in mice peritonitis models and no pathogen were detected after 24 h of treatment. Further, no pathological phenomenon in lung and low level of inflammatory cytokines in blood were detected. These results indicate that NZ2114 has the potential to be a new antimicrobial agent candidate for the clinical treatment of infection caused by S. suis type 2. [ABSTRACT FROM AUTHOR]

The family of antimicrobial peptide, cathelicidins, which plays important roles against infections in animals, has been identified from many species. Here, we identified a novel avian cathelicidin ortholog from ducks and named dCATH. The cDNA sequence of dCATH encodes a predicted 146-amino-acid polypeptide composed of a 17-residue signal peptide, a 109-residue conserved cathelin domain and a 20-residue mature peptide. Phylogenetic analysis demonstrated that dCATH is highly divergent from other avian peptides. The α-helical structure of the peptide exerted strong antimicrobial activity against a broad range of bacteria in vitro, with most minimum inhibitory concentrations in the range of 2 to 4 μM. Moreover, dCATH also showed cytotoxicity, lysing 50% of mammalian erythrocytes in the presence or absence of 10% fetal calf serum at concentrations of 32 μM or 20 μM and killing 50% HaCaT cells at a concentration of 10 μM. The effects on bacterial outer and inner membranes, as examined by scanning electron microscope and transmission electron microscopy, indicate that dCATH kills microbial cells by increasing permeability, causing a loss of membrane integrity. [ABSTRACT FROM AUTHOR]