Isolation and identification of Salmonella pullorum bacteriophage YSP2 and its use as a therapy for chicken diarrhea.

Salmonella pullorum is the major pathogen that is harmful to the poultry industry in developing countries, and the treatment of chicken diarrhea caused by S. pullorum has become increasingly difficult. In this study, a virulent bacteriophage YSP2, which was able to specifically infect Salmonella, was isolated and characterized. Phage YSP2 was classified in the Siphoviridae family and had a short latent period of 10 min. No bacterial virulence- or lysogenesis-related ORF is present in the YSP2 genome, making it eligible for use in phage therapy. Experiments in vivo investigated the potential use of phages as a therapy against diarrhea in chickens caused by S. pullorum in a chicken diarrhea model, demonstrating that a single oral administration of YSP2 (1 × 1010 PFU/mL, 80 µL/chicken) 2 h after S. pullorum oral administration at a double median lethal dose was sufficient to protect chickens against diarrhea. Gross inspection showed that YSP2 can effectively reduce organ damage and significantly relieve hemorrhage in the intestine and liver tissue. Moreover, YSP2 can maintain a high curative effect when diluted to 108 PFU/mL. In light of its therapeutic effect on chicken diarrhea, YSP2 may serve as an alternative treatment strategy for infections caused by S. pullorum.

Design, expression, and characterization of the hybrid antimicrobial peptide T-catesbeianin-1 based on FyuA.

The overuse of antibiotics has resulted in the emergence of antibiotic-resistant bacteria, which presents an urgent need for new antimicrobial agents. At present, antimicrobial peptides have attracted a great deal of attention from researchers. However, antimicrobial peptides often affect a broad range of microorganisms, including the normal flora in a host organism. In the present study, we designed a novel hybrid antimicrobial peptide, expressed the hybrid peptide, and studied its specific target. The hybrid peptide, named T-catesbeianin-1, which includes the FyuA-binding domain of pesticin and the peptide catesbeianin-1, was designed and expressed in Pichia pastoris X-33. Then, we determined the antimicrobial activity, cytotoxicity, and specific target of the peptide. T-catesbeianin-1 has strong antimicrobial activity and binds to FyuA to inhibit or kill Escherichia coli present in clinical specimens and mixed-species culture. In summary, these findings suggested that T-catesbeianin-1 might be promising and specific antibiotic agent for therapeutic application against fyuA+ E. coli.

Catesbeianin-1, a novel antimicrobial peptide isolated from the skin of Lithobates catesbeianus (American bullfrog).

OBJECTIVES: To identify and characterize a novel antimicrobial peptide, catesbeianin-1. RESULTS: Catesbeianin-1 is 25 amino acids long and is α-helical, cationic and amphipathic. It had antimicrobial activity against Gram-positive and Gram-negative bacteria. It was resistant against trypsin and pepsin. Catesbeianin-1 exhibited moderate hemolytic activity (approx 8%) at 100 µg/ml, and its HC50 (50% hemolytic concentration) was 300 µg/ml. Its cytotoxicity was approx 10-20% at 100 µg/ml, and its CC50 (50% cytotoxic concentration) was >100 µg/ml. The LD50 of catesbeianin-1 in mice was 80 mg/kg. At 3.1 µg/ml, catesbeianin-1 significantly inhibited the growth of methicillin-resistant Staphylococcus aureus. CONCLUSIONS: A new antimicrobial peptide from the skin of Lithobates catesbeianus (American bullfrog) may represent a template for the development of novel antimicrobial agents.