In Vivo Horizontal Gene Transfer of the Carbapenemase OXA-48 During a Nosocomial Outbreak

Background. OXA-48 is a highly prevalent carbapenemase and has been isolated worldwide. Here, we investigate the in vivo horizontal gene transfer (HGT) of bla(OXA-48) from Klebsiella pneumoniae to Escherichia coli in an infected patient. Methods. Bacterial isolates were characterized by susceptibility testing, multilocus sequence typing, DiversiLab, and plasmid analyses. Transferability of bla(OXA-48) was evaluated by in vitro transconjugation using the outbreak strain and E. coli J53. In vivo transconjugation was investigated using the larvae of the greater wax moth (Galleria mellonella) and low-complexity-microbiota mice. Results. OXA-48-harboring K. pneumoniae isolates belonging to ST14 were isolated during a nosocomial outbreak from 6 patients. Molecular and epidemiological analyses revealed the HGT of an approximately 60-kb OXA-48-containing IncL/M-type plasmid from K. pneumoniae to E. coli belonging to the novel ST666 in a patient. In vitro conjugation experiments revealed a transconjugation frequency of 8.7 x 10(-7). HGT of OXA-48 in a newly developed in vivo model using G. mellonella larvae revealed a higher transconjugation frequency of 1.3 x 10(-4). The conjugation frequency of OXA-48 from K. pneumoniae and E. coli in the gut of low-complexity-microbiota mice was determined to be 2.9 x 10(-5). Conclusions. The in vivo intergenus gene transfer of OXA-48 in the gut of an infected patient was verified in vitro and in 2 in vivo models, which both showed even higher transmission frequencies vs in vitro conditions. This implies that the current in vitro protocols might not correctly reflect the HGT of carbapenemase genes in vivo.