A separate problem exists with laboratory testing for reduced susceptibility to ciprofloxacin; current recommendations are that isolates should be tested simultaneously against ciprofloxacin (CIP) and against nalidixic acid (NAL), that isolates sensitive to both CIP and NAL should be reported as "sensitive to ciprofloxacin", and that isolates sensitive to CIP but not to NAL should be reported as "reduced sensitivity to ciprofloxacin". But an analysis of 271 isolates found that around 18% of isolates with a reduced susceptibility to fluoroquinolones, the class which CIP belongs (MIC 0.125–1.0 mg/L), would not be detected by this method.
