Background: Klebsiella pneumoniae, an environmental pathogen causing mastitis in dairy cattle, is often resistant to antibiotics.K. pneumoniaewas used as the host bacteria to support bacteriophage replication; 2 bacteriophages, CM8-1 and SJT-2 were isolated and considered to have therapeutic potential. In the present study, we determined the ability of these 2 bacteriophages to mitigate cytotoxicity, pathomorphological changes, inflammatory responses and apoptosis induced byK. pneumoniae(bacteriophage toK. pneumoniaeMOI 1:10) in bovine mammary epithelial cells (bMECs) culturedin vitro.Results: Bacteriophages reduced bacterial adhesion and invasion and cytotoxicity (lactate dehydrogenase release). Morphological changes in bMECs, including swelling, shrinkage, necrosis and hematoxylin and eosin staining of cytoplasm, were apparent 4 to 8 h after infection withK. pneumoniae, but each bacteriophage significantly suppressed damage and decreased TNF-α and IL-1β concentrations.K. pneumoniaeenhanced mRNA expression of TLR4, NF-κB, TNF-α, IL-1β, IL-6, IL-8, caspase-3, caspase-9 and cyt-c in bMECs and increased apoptosis of bMECs, although these effects were mitigated by treatment with either bacteriophage for 8 h.Conclusions: Bacteriophages CM8-1 and SJT-2 mitigatedK. pneumoniae-induced inflammation in bMECs cultured in vitro. Therefore, the potential of these bacteriophages for treating mastitis in cows should be determined in clinical trials.

Antibiotic resistance genes (ARGs) have become recognized contaminants and pose a high public health risk. The animal gut microbiota is a reservoir of ARGs, but the knowledge of the origin and dissemination of ARGs remains unclear. In this study, we provide a comprehensive profile of ARGs and mobile genetic elements in the gut microbiota from 30 bovines to study the impact of modern antibiotics on resistance. A total of 42 ARG types were detected by annotating the metagenomic sequencing data from Comprehensive Antibiotic Resistance Database (CARD). We found that the diversity and abundance of ARGs in individual yaks were significantly lower than those in dairy and beef cattle ( p < 0.0001). The results of heat map and single nucleotide polymorphism clustering suggest that ARGs from dairy and beef cattle are more similar, whereas those from yaks cluster separately. The long-term use of antibiotics may contribute to this difference, suggesting that antibiotic consumption is the main cause of ARG prevalence. Furthermore, abundant insertions were also found in this study, signifying a strong potential for horizontal transfer of ARGs among microbes, especially pathogens.

This experiment aimed to investigate the effects of Quercetagetin (QG) on the growth performance, antioxidant capacity, and cecal microbiota of broilers. Two hundred and forty 21-day-old WOD168 broilers with similar body weights were randomly divided into five groups of six replicates each with eight chickens. The control group was fed a basal diet composed of corn and soybean meal, while the experimental groups received basal diets supplemented with 0, 10, 20, and 40 mg/kg QG, along with intraperitoneal injection of 20 mg/kg body weight Diquat (DQ). The experiment lasted for 21 days. The results showed that: (1) QG significantly alleviated the decrease in average daily feed intake and average daily gain induced by Diquat, reduced the elevation of serum ACTH content, and significantly increased GH content (P < 0.05); (2) QG supplementation significantly mitigated the decrease in serum CAT activity and duodenal GSH-Px activity induced by Diquat (P < 0.05), as well as the increase in MDA content (P < 0.05); additionally, QG significantly increased the gene expression levels of GSH-Px, Nrf2, and Keap1 (P < 0.05); (3) Alpha and Beta diversity analysis revealed that QG supplementation significantly increased the cecal microbial OTUs and Chao1 index of broilers (P < 0.05). At the phylum level, compared with the Diquat group, the LQG group significantly decreased the relative abundance of Firmicutes (P < 0.05) and significantly increased the relative abundance of Bacteroidota (P < 0.05). At the genus level, compared with the CON group, the Diquat group significantly decreased the abundance of Lactobacillus and Alistipes (P < 0.05), while QG supplementation significantly alleviated the decrease in the abundance of Lactobacillus and Alistipes (P < 0.05). In conclusion, the addition of an appropriate amount (20 mg/kg) of QG to the diet can promote the growth of broilers, enhance antioxidant capacity, and improve intestinal health.

Salmonella enteritidis plays a significant role in zoonotic infections. This pathogen settles in the intestinal tract of poultry and contaminates meat and egg products during production for slaughter. Consequently, it can also be transmitted to humans along the food chain, posing a significant risk to public health. Bacteriophages offer a viable substitute for antibiotics in treating Salmonella enteritidis due to their specific bactericidal effect and safety. This study aimed to investigate the protective effect of bacteriophage against Salmonella enteritidis infection in chicken intestinal epithelial cells. Chicken intestinal epithelial cells were treated with various concentrations of bacterial suspension, and the impact on cell damage was assessed by measuring changes in cell viability and observing structural changes via transmission electron microscopy. In the phage protection experiment, the phages were co-incubated with Salmonella enteritidis for 2, 4, and 6 h. Thereafter, the adhesion rate and invasion rate of bacteria and gene transcription levels of Occludin, Claudin-1, ZO-1, NF-κB p65, TNF-α and IL-6 in cells were determined. The results indicated that the phage could significantly reduce both adhesion and invasion rates of Salmonella enteritidis at MOI = 10 (P < 0.05). Following phage treatment of the co-culture of chicken intestinal epithelial cells and Salmonella enteritidis (CICC10467), there was a significant reduction in the gene expression of pro-inflammatory cytokines NF-κB p65, TNF-α and IL-6, and a significant increase in the gene expression of anti-inflammatory cytokines Occludin, Claudin-1, and ZO-1. This indicates that the phage can inhibit the infection of chicken small intestinal epithelial cells by Salmonella enteritidis. Furthermore, phages were able to significantly alleviate inflammation and barrier integrity disruption caused by the bacteria in the co-culture. These observations suggest that phages are promising candidates for preventing and treating gastrointestinal bacterial infections.

This study investigates the effects of quercetagetin (QG) supplementation on the antioxidant capacity, liver mitochondrial function, and cecal microbiota of broilers raised under high-density conditions. A 2 × 2 factorial design with 144 one-day-old WOD168 broilers, which were allocated to two stocking densities (LD: 4 birds per cage, equivalent to 11.1 birds per square meter; HD: eight birds per cage, equivalent to 22.2 birds per square meter) and two levels of dietary supplementation of QG (0 and 20 mg/kg). At the conclusion of day 21, broilers of similar body weights were randomly allocated into four groups (22 to 42 d): control (CON), QG treatment (QG), high stocking density (HSD), and high stocking density with QG supplementation (H_QG). The results demonstrated that HD groups significantly reduced broiler growth performance, including body weight (BW), average daily gain (ADG), and average daily feed intake (ADFI) (p < 0.05). Additionally, HD groups increased serum stress hormone levels (CORT and ACTH), pro-inflammatory cytokines (IL-1β and IL-6) (p < 0.05), while decreasing liver antioxidant enzyme activities (GSH-Px, T-SOD), serum CAT and T-SOD activities, and mitochondrial function (GSH, complex I-III, ATP contents) (p < 0.05). However, dietary supplementation with 20 mg/kg QG significantly alleviated the negative effects induced by HSD, restoring growth performance, stress hormone levels, immune parameters, and liver antioxidant and mitochondrial function. Moreover, QG supplementation markedly improved cecal microbiota composition, enhancing gut health. Correlation analysis revealed a strong association between microbial composition and overall broiler health, indicating that gut microbiota plays a critical role in mediating these beneficial effects. In conclusion, QG exhibits protective effects against oxidative stress, mitochondrial dysfunction, and gut microbiota imbalance induced by high-density rearing, suggesting its potential as a functional feed additive to improve broiler health under intensive farming conditions.