AUTHOR=Hamprecht Axel , Sommer Julian , Willmann Matthias , Brender Christina , Stelzer Yvonne , Krause Felix F. , Tsvetkov Tsvetan , Wild Florian , Riedel-Christ Sara , Kutschenreuter Julia , Imirzalioglu Can , Gonzaga Aitor , Nübel Ulrich , Göttig Stephan 

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

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02509

DOI=10.3389/fmicb.2019.02509

ISSN=1664-302X

ABSTRACT=<p>OXA-48 is the most common carbapenemase in Enterobacterales in Germany and one of the most frequent carbapenemases worldwide. Several reports have associated <italic>bla</italic><sub>OXA</sub><sub>–</sub><sub>48</sub> with a virulent host phenotype. To challenge this hypothesis, 35 OXA-48-producing clinical isolates of <italic>Escherichia coli</italic> (<italic>n</italic> = 15) and <italic>Klebsiella pneumoniae</italic> (<italic>n</italic> = 20) were studied <italic>in vitro</italic>, <italic>in vivo</italic> employing the <italic>Galleria mellonella</italic> infection model and by whole-genome sequencing. Clinical isolates belonged to 7 different sequence types (STs) in <italic>E. coli</italic> and 12 different STs in <italic>K. pneumoniae</italic>. In 26/35 isolates <italic>bla</italic><sub>OXA–</sub><sub>48</sub> was located on a 63 kb IncL plasmid. Horizontal gene transfer (HGT) to <italic>E. coli</italic> J53 was high in isolates with the 63 kb IncL plasmid (transconjugation frequency: ∼10<sup>3</sup>/donor) but low in isolates with non-IncL plasmids (&lt;10<sup>–6</sup>/donor). Several clinical isolates were both highly cytotoxic against human cells and virulent <italic>in vivo</italic>. However, 63 kb IncL transconjugants generated from these highly virulent isolates were not more cytotoxic or virulent when compared to the recipient strain. Additionally, no genes associated with virulence were detected by <italic>in silico</italic> analysis of OXA-48 plasmids. The 63 kb plasmid was highly stable and did not impair growth or fitness in <italic>E. coli</italic> J53. In conclusion, OXA-48 clinical isolates in Germany are diverse but typically harbor the same 63 kb IncL plasmid which has been reported worldwide. We demonstrate that this 63 kb IncL plasmid has a low fitness burden, high plasmid stability and can be transferred by highly efficient HGT which is likely the cause of the rapid dissemination of OXA-48 rather than the expansion of a single clone or gain of virulence.</p>