INTRODUCTION OF PLASMID CARRYING AN INCOMPLETE SET OF GENES FOR AEROBACTIN PRODUCTION ALTERS VIRULENCE OF ESCHERICHIA-COLI HB101

The aerobactin-mediated iron uptake system is encoded by pCoIV-K30 and other CoIV plasmids. it has been known to contribute to the ability o f Escherichia coil to cause pyelonephritis and cystitis. In the presen t study an attempt was made to evaluate the contribution of an incompl ete set of genes for aerobactin synthesis to the virulence of Escheric hia coil HB101. Escherichia coli HB101 was transformed with a recombin ant plasmid pJHCV-12 (Tet(r) and Kan(r)) carrying aerobactin genes (co mplete first two genes, iucA and iucB and part of the third gene iucC) from pCoIV-K30. Both HB101 and a transformant H10 grew equally well w hen applied to a Vero cell line. These strains were tested for their a bility to invade and kill Vero cells in monolayers. Light micrographs showed cell damage by the transformant carrying pJHCV-12 plasmid and t his cytotoxic effect correlated with the amount of lactate dehydrogena se (LDH) released. In contrast, strain HB101 and HB101 containing pare nt vector pVK102 did not produce any cytotoxic effects. When the abili ty of these strains to produce ascending pyelonephritis in a mouse mod el was compared, the transformant established itself better in renal t issue than the control strain HB101, when assessed 2h, 4 h and 5 days post-infection.