Impact of the host and medical treatment on the transfer of a blaVIM-1 IncN plasmid in an in vivo zebrafish gut model
The purpose was to study the transfer of a ~50kb IncN multidrug-resistance plasmid with blaVIM-1 from Klebsiella pneumoniae to Escherichia coli under 8 different mono and combination therapy conditions using an in vivo zebrafish infection-and-treatment model. Two days after oral infection of zebrafish with the K. pneumoniae donor strain and the recipient E. coli, the posterior intestinal segment were sampled to harvest bacterial growth on selective agar plates. Parallel in vitro plasmid-transfer was studied in broth-mating experiments. None of the culturable zebrafish gut bacteria were detected on the selective plates for transconjugants. Certain treatments with sub-MIC of ciprofloxacin (p<0.05) and gentamicin (p<0.1) increased plasmid transfer to recipient E. coli, whereas treatment with non-bactericidal prednisolone (p<0.05) resulted in lower number of transconjugants compared to the numbers in placebo-treated animals. No transconjugants were detected after administration of therapeutic concentrations of gentamicin. This in vivo transfer event was further investigated in an in vitro model. Sub-MIC ciprofloxacin treatment resulted in relatively higher plasmid transfer frequencies compared to treated controls in both in vivo and in vitro assays. Surprisingly, compared to the in vitro transfer-experiments ~100 times higher transfer frequency was found in the zebrafish gut.