Evaluation of the efficacy of the antimicrobial peptide HJH-3 in chickens infected with Salmonella Pullorum

Gallnut tannic acid alleviates gut damage induced by Salmonella pullorum in broilers by enhancing barrier function and modulating microbiota

Pullorum disease (PD) is a bacterial infection caused by Salmonella pullorum (S. pullorum) that affects poultry. It is highly infectious and often fatal. Antibiotics are currently the mainstay of prophylactic and therapeutic treatments for PD, but their use can lead to the development of resistance in pathogenic bacteria and disruption of the host's intestinal flora. We added neomycin sulfate and different doses of tannic acid (TA) to the drinking water of chicks at 3 days of age and infected them with PD by intraperitoneal injection of S. pullorum at 9 days of age. We analyzed intestinal histopathological changes and the expression of immune-related genes and proteins by using the plate smear method, histological staining, real-time fluorescence quantitative PCR, ELISA kits, and 16S rRNA Analysis of intestinal flora. The results demonstrate that S. pullorum induces alterations in the immune status and impairs the functionality of the liver and intestinal barrier. We found that tannic acid significantly ameliorated S. pullorum-induced liver and intestinal damage, protected the intestinal physical and chemical barriers, restored the intestinal immune barrier function, and regulated the intestinal flora. Our results showed that TA has good anti-diarrhoeal, growth-promoting, immune-regulating, intestinal barrier-protecting and intestinal flora-balancing effects, and the best effect was achieved at an additive dose of 0.2%.

Salmonellosis: An Overview of Epidemiology, Pathogenesis, and Innovative Approaches to Mitigate the Antimicrobial Resistant Infections

Salmonella is a major foodborne pathogen and a leading cause of gastroenteritis in humans and animals. Salmonella is highly pathogenic and encompasses more than 2600 characterized serovars. The transmission of Salmonella to humans occurs through the farm-to-fork continuum and is commonly linked to the consumption of animal-derived food products. Among these sources, poultry and poultry products are primary contributors, followed by beef, pork, fish, and non-animal-derived food such as fruits and vegetables. While antibiotics constitute the primary treatment for salmonellosis, the emergence of antibiotic resistance and the rise of multidrug-resistant (MDR) Salmonella strains have highlighted the urgency of developing antibiotic alternatives. Effective infection management necessitates a comprehensive understanding of the pathogen's epidemiology and transmission dynamics. Therefore, this comprehensive review focuses on the epidemiology, sources of infection, risk factors, transmission dynamics, and the host range of Salmonella serotypes. This review also investigates the disease characteristics observed in both humans and animals, antibiotic resistance, pathogenesis, and potential strategies for treatment and control of salmonellosis, emphasizing the most recent antibiotic-alternative approaches for infection control.

Brevibacillus brevis HNCS-1: a biocontrol bacterium against tea plant diseases

As a biocontrol bacteria, Brevibacillus has been the subject of extensive research for agricultural applications. Antibacterial peptides (AMPs) are the main antibacterial products of Brevibacillus. This study isolated a strain of Br. brevis HNCS-1 from tea garden soil, and the strain has an antagonistic effect against five types of pathogens of tea diseases, namely Gloeosporium theae-sinensis, Elsinoe leucospira, Phyllosticta theaefolia, Fusarium sp., and Cercospora theae. To determine the genetic characteristics implicated in the biocontrol mechanism, the genome sequence of the HNCS-1 strain was obtained and analyzed further, and the data are deposited in the GenBank repository (No. CP128411). Comparative genomics analyses revealed that the HNCS-1 strain and 17 public Br. brevis share a core genome composed of 3,742 genes. Interestingly, only one non-ribosomal peptide synthetase (NRPS) gene cluster annotated as edeine is present in the core genome. And UHPLC-MS/MS detection results showd that edeine B and edeine A were the principal antibacterial peptides in the HNCS-1 strain. This study proves that edeine is the main antibacterial peptide of Br. brevis, and provides a new strategy for the identification of antibacterial products from other biocontrol bacteria.

Bithionol Restores Sensitivity of Multidrug-Resistant Gram-Negative Bacteria to Colistin with Antimicrobial and Anti-biofilm Effects

Being among the few last-resort antibiotics, colistin (COL) has been used to treat severe infectious diseases, such as those caused by multidrug-resistant Gram-negative bacteria (MDR GNB). However, the appearance of colistin-resistant (COL-R) GNB has been frequently reported. Therefore, novel antimicrobial strategies need to be urgently sought to address this resistance challenge. In the present study, antimicrobial drug screening conducted revealed that bithionol (BT), approved by the Food and Drug Administration and used as an anthelminthic drug for paragonimiasis, exhibited a synergistic antibacterial effect with COL. Clinically isolated COL-R GNB were used as candidates to evaluate the synergistic antibacterial activity. The results revealed that BT could significantly reverse the sensitivity of COL-R GNB to COL. Furthermore, the combined application of BT and COL can reduce bacterial biofilm formation and have a scavenging effect on the mature biofilm in vitro. The damage caused to the bacterial cell membrane integrity by the BT/COL combination was observed under a fluorescence microscope. The fluorescence intensity of reactive oxygen species also increased in the experimental group. The BT/COL combination also exhibited a synergistic antibacterial effect in vivo. Importantly, BT was confirmed to be safe at the highest concentrations that exerted synergistic effects on all tested strains. In conclusion, our findings demonstrated that BT exerted synergistic antimicrobial and anti-biofilm effects when combined with COL against MDR organisms, especially COL-R GNB, in vitro and in vivo. The findings thus provide a reference for the clinical response to the serious challenge of MDR GNB and the exploitation of the potential antibacterial activities of existing clinical non-antibacterial drugs.

High expression of antimicrobial peptides cathelicidin-BF in Pichia pastoris and verification of its activity

Antibacterial peptides are endogenous polypeptides produced by multicellular organisms to protect the host against pathogenic microbes, they show broad spectrum antimicrobial activities against various microorganisms and possess low propensity for developing resistance. The purpose of this study is to develop recombinant antibacterial peptide cathelicidin-BF by genetic engineering and protein engineering technology, and study its antibacterial activity in vitro and in vivo, so as to provide reference for the production and application of recombinant antibacterial peptide cathelicidin-BF. In this study, on account of Pichia pastoris eukaryotic expression system, we expressed and prepared antibacterial peptide cathelicidin-BF. Then, the minimum inhibitory concentration of antibacterial peptide cathelicidin-BF and the comparison with the antibacterial activity of antibiotics were determined through the antibacterial experiment in vitro. Chickens as infection model were used to verify the antibacterial peptide activity in vivo. The results show that the bacteriostatic ability of antibacterial peptide cathelicidin-BF is similar to that of antibiotics in certain concentration, and can reach the treatment level of antibiotics. Although the mode of administration of antibacterial peptide is still limited, this study can provide reference for the future research of antibacterial peptide.