The functions and roles of OMVs on ARG and virulent gene transfer and dissemination have been reported in numerous Gram-negative bacteria. However, the role of OMVs in mediating antibiotic resistance in A. paragallinarum has not been reported.

Infectious coryza is an acute upper respiratory tract infectious disease caused by Avibacterium paragallinarum, which can cause growth retardation and egg production decline of bred chickens, and bring great economic losses to poultry industry. A. Paragallinarum is a Gram-negative bacterium andcan release outer membrane vesicles (OMVs).In this study, a comparative genomic analysis of A. Paragallinarumisolate P4chr1 and its OMVs were carried out, and the ability to transfer antibiotic resistance genes via the OMVswas studied. The sequencing and data analysis showed that genome size of A. paragallinarum P4chr1 is about 2.77 Mb and it has a 25 kb tolerance island covering 6 types of antibiotics and 11 resistance genes. The genome size of its OMVs is about 2.69 Mb, covering 97% genome length and almost all gene sequences of P4chr1. When purified and DNase treated A. paragallinarum P4chr1 OMVs were co-cultured with antibiotic sensitive A. paragallinarum Modesto strain on an antibiotic containing plate, the colonies grown on the plate were detected corresponding antibiotic resistance gene (ARG).However, antimicrobial susceptibility test exposed that drug resistance genes delivered by OMVs were not persistent, they only existed temporarily on the antibiotic plates. The antibiotic resistance and ARGs disappeared at second bacterial passage. Overall, this study is the first report to compare genomic characteristics of OMVs with its parent A. paragallinarum strain, and to study A. paragallinarum ARG transfer via OMVs. This work has provided useful data for further study on the issue of non-plasmid ARG transfer mediated by A. paragallinarum OMVs.

Toosendanin (TSN) is an active compound from the fruit of Melia toosendan Sieb et Zucc. TSN has been shown to have broad‐spectrum anti‐tumour activities in human cancers. However, there are still many gaps in the knowledge of TSN on canine mammary tumours (CMT). CMT‐U27 cells were used to select the optimal acting time and best concentration of TSN to initiate apoptosis. Cell proliferation, cell colony formation, cell migration and cell invasion were analysed. The expression of apoptosis‐related genes and proteins were also detected to explore the mechanism of action of TSN. A murine tumour model was established to detect the effect of TSN treatments. The results showed that TSN decreased cell viability of migration and invasion, altered CMT‐U27 cell morphology, and inhibited DNA synthesis. TSN‐induced cell apoptosis by upregulating BAX, cleaved caspase‐3, cleaved caspase‐9, p53 and cytochrome C (cytosolic) protein expression, and downregulating Bcl‐2 and cytochrome C (mitochondrial) expression. In addition, TSN increased the mRNA transcription levels of cytochrome C, p53 and BAX, and decreased the mRNA expression of Bcl‐2. Furthermore, TSN inhibited the growth of CMT xenografts by regulating the expression of genes and proteins activated by the mitochondrial apoptotic pathway. In conclusion, TSN effectively inhibited cell proliferation, migration and invasion activity, as well as induced CMT‐U27 cell apoptosis. The study provides a molecular basis for the development of clinical drugs and other therapeutic options.