Evaluation of susceptibility testing to detect fluoroquinolone resistance mechanisms in Streptococcus pneumoniae

To determine if susceptibility testing of Streptococcus pneumoniae could de tect those isolates that had one of the recognized mechanisms of fluoroquin olone resistance, 101 isolates were selected; the levofloxacin MIC for 28 o f these isolates was greater than or equal to4 mug/ml. Only isolates with b oth parC and gyrA mutations or with no recognized resistance mechanisms wer e reliably identified by using these results. Isolates,vith only a parC mut ation could not be detected reliably using any susceptibility testing metho d.