Newcastle disease virus (NDV) is one of the highly contagious pathogens causing devastating economic effects on the global poultry industry. In the present study, three 1-formyl-β-carboline derivatives (compounds 6, 7, and 9) were found to be potent inhibitors of different genotypes of NDV with IC₅₀ values within 10 μM, which are similar to ribavirin. The virus titers were decreased by the presence of 1-formyl-β-carboline derivatives in a dose-dependent manner, and the inhibition rate was found to exceed 90% at the concentration of 20 μM. These compounds mainly suppressed the adsorption and entry processes of NDV lifecycle. Through DARTS, CETSA, and RBC binding assay, these compounds were identified as novel HN inhibitors, which could directly interact with the NDV HN protein to affect the adsorption of NDV. Furthermore, they could inhibit the entry of NDV through suppressing the PI3K/Akt pathway rather than the ERK pathway. The PI3K/Akt pathway was proved to be involved in NDV entry. Our findings reveal a unique mechanism through which 1-formyl-β-carboline derivatives restrain NDV infection. Moreover, these compounds represent suitable scaffolds for designing novel HN inhibitors.

The genomic context of the mcr-1 gene in Escherichia coli from animal feces has been widely reported. However, less is known about the mcr-1-carrying plasmid characteristics and other functional regions of Escherichia coli isolates from animal organs with lesions. The present study investigated the antimicrobial resistance, population structure, and genetic features of mcr-1-positive Escherichia coli strains isolated from animal organs with lesions. The antimicrobial susceptibility testing indicated that 24 mcr-1-positive Escherichia coli isolates were resistant to at least three or all antimicrobial categories. MLST analysis suggested that the dominant clone complexes (CC) were mainly CC156, CC448, and CC10. In addition, ST10596, a newly discovered sequence type in swine, failed to be classified. Meanwhile, the mcr-1 gene located on the different plasmids was successfully transferred to the recipients, and whole-genome sequencing indicated the mcr-1 gene was embedded in mcr-1-pap2 cassette but not flanked by ISApl1. The mcr-1 gene is located on the chromosome and embedded in Tn6330. Furthermore, NDM-5 was found on the IncX3-type plasmid of J-8. The virB6 and traI gene of type IV secretion system (T4SS) were truncated by IS2 and IS100 and located on the IncX4- and the IncHI2/HI2A/N-type plasmids, respectively. The multidrug-resistant (MDR) region of IncHI2/HI2A/N-type plasmids contained two class 1 integrons (In0, In640) and four composite transposons (Tn4352, Tn6010, cn_4692_IS26, cn_6354_IS26). Overall, 24 mcr-1-positive Escherichia coli isolates in our study showed MDR, or even extensively drug resistant (XDR), and exhibited population diversity. The T4SS gene truncation by the insertion sequence may affect the efficiency of plasmid conjugative transfer. Furthermore, the class 1 integrons and composite transposons in the MDR region of IncHI2/HI2A/n-type plasmid contributed to the multireplicon plasmid formation, the acquisition, and transfer of antimicrobial resistance genes (ARGs).

Trueperella pyogenes is a significant opportunistic pathogen that causes substantial economic losses in animal agriculture due to its ability to infect various animal tissues and organs. Limited research has been conducted on the prevalence and biological characteristics of T. pyogenes isolated from sheep and goats. This study aimed to isolate T. pyogenes from clinical samples of sheep and goats in western China, examining genetic evolutionary relationships, antibiotic resistance, and virulence genes. Between 2021 and 2023, standard bacteriological methods were used to isolate and identify T. pyogenes from 316 samples (209 from goats and 107 from sheep) collected from 39 farms. Susceptibility to 14 antibiotics was tested using broth microdilution per CLSI guidelines, and PCR detected eight virulence genes. Whole-genome sequencing analyzed genetic relationships and gene carriage status in 39 isolates. The results indicated that 86 strains of T. pyogenes were isolated from 316 samples, yielding an isolation rate of 27.2% (goats n = 47, 22.5%; sheep n = 39, 36.4%). The virulence genes plo, cbpA, nanH, nanP, fimA, fimC, and fimE were present in 100%, 66.7%, 64.1%, 71.8%, 69.2%, 59.0%, and 82.1% of isolates, respectively, with none carrying the fimG gene. The dominant virulence genotype was plo/nanH/nanP/fimA/fimC/fimE. The isolates exhibited resistance to erythromycin (44.2%, 38/86), gentamicin (38.4%, 33/86), sulfamethoxazole/trimethoprim (37.2%, 32/86), tetracycline (32.6%, 28/86), and streptomycin (32.6%, 28/86), and low resistance to chloramphenicol (14.0%, 12/86), ciprofloxacin (7.0%, 6/86), penicillin (5.8%, 5/86), and clindamycin (4.7%, 4/86). All isolates were susceptible to cefotaxime, vancomycin, and linezolid. Among the 86 isolates, 37 (43.0%) displayed multidrug resistance (MDR) characteristics. The whole genome sequencing of 39 isolates identified eight types of resistance genes, including ant(2″)-Ia, ant(3″)-Ia, cmlA1, cmx, erm(X), lnu(A), sul1, and tet(W). Except for tet(W), erm(X), and sul1, the other resistance genes were reported for the first time in T. pyogenes isolated in China. The drug susceptibility test results and resistance gene detection for the isolated strains were consistent for tetracycline, erythromycin, gentamicin, and sulfisoxazole. Similar allelic profiles and genetic evolutionary relationships were found among isolates from different farms. This study highlights the antibiotic resistance status and virulence gene-carrying rate of Trueperella pyogenes, providing a basis for clinical medication.

Staphylococcus aureus (S. aureus) is a major etiological agent of mastitis in dairy goats and a potential reservoir of antimicrobial resistance (AMR). In the present study, the prevalence and antimicrobial susceptibility of S. aureus isolated from goat milk in Shaanxi Province, China, was investigated and the genomic features of a multidrug-resistant (MDR) subset were characterized. A total of 184 (10.7%) S. aureus isolates were recovered from 1720 milk samples collected from 19 dairy farms. Antimicrobial susceptibility testing against 18 agents showed that the isolates exhibited an overall favorable susceptibility profile, with resistance remaining uncommon for most drugs tested. However, nine isolates (4.9%) were classified as MDR, including three (1.6%) methicillin-resistant S. aureus (MRSA) isolates. Although MDR was uncommon in the sample, genomic analysis showed that the MDR subset comprised a limited number of high-risk lineages, including MRSA ST59 and methicillin-susceptible S. aureus (MSSA) ST398. Comparative phylogenetic analysis indicated that the MRSA ST59 and MSSA ST398 isolates were genetically related to publicly available human and porcine-associated genomes, respectively, consistent with possible host spillover. In addition, the MSSA ST398 and ST522 isolates contained putative host-associated virulence factor variants that warrant further functional validation. Overall, the present study provides region-specific surveillance data on milk-associated S. aureus in dairy goats and highlights the importance of continued integrated surveillance of high-risk S. aureus lineages within the One Health framework.