Effects of iron on the growth, biofilm formation and virulence of Klebsiella pneumoniae causing liver abscess

Abstract

Background: Klebsiella pneumoniae is considered as the most clinically relevant species of Enterobacteriaceae, known to cause severe infections including liver abscesses. To the best of our knowledge,iron in human body primarily gathers in liver. Further understanding of effects of iron on K. pneumoniae causing liver abscess is a promising way to elucidate the mechanism of poor prognosis of liver abscess. Results: All tested K. pneumoniae including those collected from liver abscess and other sterile sites and K. pneumoniae ATCC 700603 cultured in LB broth containing 50 μM iron grew optimally and were in possession of the strongest biofilm formation ability, while worst growth and biofilm formation ability of the strains cultured in iron-deplete environment were observed. The infection model of G. mellonella larvae showed the virulence of K. pneumoniae cultured with additional iron was significantly higher than cultured with iron chelator (P<0.05). The relative expression level of the four siderophores genes (iucB, iroB, irp1, entB) in K. pneumoniae strains isolated from liver abscess cultured with additional iron was lower than that with iron chelator. Conclusions: It is suggested by our research that iron in the environment can promote the growth and enhance the biofilm formation ability of K. pneumoniae and the lower expression of siderophores genes may be one of the mechanisms of iron affecting the virulence of liver abscess-causing K. pneumoniae. Further deeper evaluation of these phenomenons is warranted.