Contribution of the FeoB transporter to Streptococcus suis virulence

The contribution of iron transporter systems encoded by feo genes to the pathogenic traits of streptococci is largely unknown, despite the fact that those systems are required for the full virulence of several gram-negative bacterial species. In this work, we show that the swine pathogen and zoonotic agent Streptococcus suis has a feoAB operon similar to that encoding an iron transporter system in Escherichia coli. Electrophoretic mobility assays and transcriptional analyses confirmed that the expression of S. suis feo genes is under the negative control of the ferric uptake regulator (Fur) protein. In vivo trials in mice using a feoB defective mutant strain were carried out to investigate the contribution of this gene to the virulence of S. suis. The results showed that the median lethal dose (LD50) of the mutant was approximately 10-fold higher than that of the wild-type parent strain. These data suggest that the Feo metal transporter plays a significant role in streptococcal infectious disease. This is in contrast to previous results reported for this same gene in other gram-positive bacterial species.