Whole genome sequencing analyses of Chinese Glaesserella parasuis isolates reveal insights into their genomic characterization, virulence genes and antibiotic resistance genes

Glaesserella parasuis is a pathogen that frequently targets the upper respiratory tract of pigs, and it poses a considerable threat to the pig industry. The aim of this study is to enrich the genetic database of G. parasuis, as well as increase the understanding of the population structure, genetic evolutionary characteristics, potential virulence factors and antibiotic resistance genes (ARGs) associated with this pathogen. This study utilized whole genome sequencing (WGS) to conduct genomic analyses on 123 G. parasuis isolates that were isolated from diseased pigs between 2017 and April 2022. The findings of this study indicated that there was variation in both genome size (2.12 Mb ~ 2.54 Mb) and G + C content (39.50% ~ 39.99%). Multilocus sequence typing (MLST) analysis revealed 99 STs out of the 123 G. parasuis isolates, with 83 STs (83.84%) being new discoveries. Phylogenetic analysis revealed two major lineages distinguished by serovars and STs. Potential virulence genes (tufA, lonA, and apa1) in G. parasuis were first reported in this study. Multiple antibiotic resistance genes (floR, tet(B), tetR, aph(3’)-Ia, strA, strB, sul2 and blaRob−1) were widely present in G. parasuis. Additionally, both integrative and conjugative elements (ICEs) as well as integron mobile elements (IMEs) were shown to be significantly present in G. parasuis. By analyzing genomic data from Chinese pig farms, we have gained valuable insights into the genotypes and antibiotic resistance of G. parasuis in swine populations, this knowledge will enhance our ability to prevent and control this disease effectively. The research findings indicate the prevalence of potential virulence factors, ARGs, ICEs and IMEs in G. parasuis.