Outer Membrane Vesicle Mediated Multidrug Resistance Gene Transfer in Avibacterium Paragallinarum

Abstract

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 and can release outer membrane vesicles (OMVs). In this study, a comparative genomic analysis of A. Paragallinarum isolate P4chr1 and its OMVs were carried out, and the ability to transfer antibiotic resistance genes via the OMVs was 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.