Gene expression analysis in the potent bactericidal activity of sitafloxacin against Streptococcus pneumoniae

We investigated the degree of expression of Streptococcus pneumoniae genes associated with bacteriolysis and cell death in relation to the rapid bactericidal activity of sitafloxacin. S. pneumoniae ATCC 49619 was added to brain heart infusion containing sitafloxacin and garenoxacin concentrations equivalent to the Cmax achieved with the usual single dose and 4 h post-Cmax concentration. RNA was extracted and cDNA was prepared using reverse transcriptase. Following RNA extraction and cDNA synthesis, quantitative PCR was performed to determine the amount of gene expression for 13 genes associated with cell death. Of the 13 genes analyzed, S. pneumoniae exposed for 10 min to a sitafloxacin concentration of 4 h post-Cmax showed 3.9 times increased expression of lytA compared to the control strain. Furthermore, we observed a slightly increased expression for cibA encoding a competence induced bacteriocin. Our study suggests that the induction of a lytic enzyme and bacteriocin may reflect gene expression in response to sitafloxacin accounting for part of its rapid bactericidal activity against S. pneumoniae.