Emergence of plasmid-mediated tigecycline, β-lactam and florfenicol resistance genes tet(X), blaOXA-347and floR in Riemerella anatipestiferisolated in China

Bacterial antimicrobial resistance (AMR) continues to develop, with the horizontal transfer of antibiotic resistance genes (ARGs) through plasmids playing a major role. Recently, the antimicrobial resistance of R. anatipestiferhas become increasingly severe, jeopardizing the development of the poultry industry. In this study, we used PromethION to determine the whole genome sequence of R. anatipestiferRCAD0416, a multidrug-resistant isolate from China. We detected a plasmid in the isolate. We named the plasmid pRCAD0416RA-1; the plasmid was 37356 bp in size with 36 putative open reading frames and included the blaOXA-347, floR, tet(X), ermF, ereD, and AadS resistance genes. Most resistance genes might be obtained from R. anatipestiferHXb2. Mobile elements and floRmight be transmitted by plasmid pB18–2 from Acinetobacter indicus, and the ICEPg6Chn1 mobile elements can be transmitted from Proteus genomosp. The plasmid pRCAD0416RA-1 was transferred to Escherichia coliK-12 × 7232 via electroporation. Subsequent antimicrobial sensitivity tests (AST) showed a noticeable levels of antimicrobial resistance to β-lactams (4–8 fold), tigecycline (8 fold), and florfenicol (8 fold). These types of antibiotics are in common clinical use. The purpose of this article is to elucidate the basic characteristics of pRCAD0416RA-1 and the level of resistance mediated by blaOXA-347, floR, and tet(X).