Correlation of MIC value and disk inhibition zone diameters in clinical Legionella pneumophila serogroup 1 isolates

ObjectivesRoutine use of disk diffusion tests for detecting antibiotic resistance in Legionella pneumophila has not been described. The goal of this study was to determine the correlation of MIC values and inhibition zone diameter (MDcorr) in clinical L. pneumophila isolates.MethodsInhibition zone diameter of 183 L. pneumophila clinical isolates were determined for ten antimicrobials. Disk diffusion results were correlated with MICs as determined earlier with E-tests.ResultsOverall the correlation of MIC values and inhibition zone diameters (MDcorr) of the tested antimicrobials is good, and all antimicrobials showed a WT distribution. Of the tested fluoroquinolones levofloxacin showed the best MDcorr. All macrolides showed a wide MIC distribution and good MDcorr. The MDcorr for cefotaxim, doxycycline and tigecycline was good, while for rifampicin and moxifloxacin, they were not.ConclusionOverall good correlation between MIC value and disk inhibition zone were found for the fluoroquinolones, macrolides and cefotaxim.