In vitro development of resistance to three quinolones in Streptococcus pneumoniae

We studied the in vitro development of resistance to ciprofloxacin, trovafloxacin and moxifloxacin in 5 strains of Streptococcus pneumoniae resistant to penicillin. We detected the great ease of in vitro development of resistance in the case of ciprofloxacin and the much reduced capacity of moxifloxacin to generate resistance (only 1 strain). Trovafloxacin generated resistance, but more slowly than ciprofloxacin. We consider that study of the capacity to generate resistance should be one of the points to consider when deciding on their large-scale use in respiratory infections, but comparative studies between in vitro and in vivo models should be carried out so as to determine the clinical repercussion of these phenomena.