Pathogenicity of Clinical OXA-48 Isolates and Impact of the OXA-48 IncL Plasmid on Virulence and Bacterial Fitness

OXA-48 is the most common carbapenemase in Enterobacterales in Germany and one of the most frequent carbapenemases worldwide. Several reports have associated bla(OXA-48) with a virulent host phenotype. To challenge this hypothesis, 35 OXA-48-producing clinical isolates of Escherichia coli (n = 15) and Klebsiella pneumoniae (n = 20) were studied in vitro, in vivo employing the Galleria mellonella infection model and by whole-genome sequencing. Clinical isolates belonged to 7 different sequence types (STs) in E. coli and 12 different STs in K. pneumoniae. In 26/35 isolates bla(OXA-48) was located on a 63 kb IncL plasmid. Horizontal gene transfer (HGT) to E. coli J53 was high in isolates with the 63 kb IncL plasmid (transconjugation frequency: similar to 10(3)/donor) but low in isolates with non-IncL plasmids (