Introduction of plasmid carrying an incomplete set of genes for aerobactin production alters virulence of Escherichia coli HB101

Abstract

The aerobactin-mediated iron uptake system is encoded by pColV-K30 and other ColV plasmids. It has been known to contribute to the ability of Escherichia coli to cause pyelonephritis and cystitis. In the present study an attempt was made to evaluate the contribution of an incomplete set of genes for aerobactin synthesis to the virulence of Escherichia coli HB101. Escherichia coli HB101 was transformed with a recombinant plasmid pJHCV-12 (Tetr and Kanr) carrying aerobactin genes (complete first two genes, iucA and iucB and part of the third gene iucC) from pColV-K30. Both HB101 and a transformant H10 grew equally well when applied to a Vero cell line. These strains were tested for their ability to invade and kill Vero cells in monolayers. Light micrographs showed cell damage by the transformant carrying pJHCV-12 plasmid and this cytotoxic effect correlated with the amount of lactate dehydrogenase (LDH) released. In contrast, strain HB101 and HB101 containing parent vector pVK102 did not produce any cytotoxic effects. When the ability of these strains to produce ascending pyelonephritis in a mouse model was compared, the transformant established itself better in renal tissue than the control strain HB101, when assessed 2h, 4 h and 5 days post-infection.