DETECTION OF QUINOLONE-RESISTANT NEISSERIA-GONORRHOEAE

The present National Committee for Clinical Laboratory Standards (NCCL S) guideline for testing Neisseria gonorrhoeae quinolone susceptibilit y defines only a susceptible category for ciprofloxacin, enoxacin, lom efloxacin, and ofloxacin, while susceptible, intermediate, and resista nt categories are defined for fleroxacin. To further define the criter ia for detection of quinolone resistance in gonococci, by standard dis k diffusion and agar dilution methodologies recommended by the NCCLS, we tested 29 strains of quinolone-resistant N, gonorrhoeae (QRNG) rece ntly isolated from ofloxacin-treated patients who were considered clin ical failures. Regression analyses were performed on these results tog ether with those of another 20 strains showing reduced susceptibility and 13 fully susceptible strains (ofloxacin MICs of less than or equal to 0.25 mu g/ml). With 5-mu g ofloxacin disks, resistance in 27 (93.1 %) of the QRNG strains (MICs of >1 mu g/ml) was detected by the criter ion of a zone diameter of <22 mm, while in the remaining 2 (6.9%), the disks failed to detect resistance. A cluster of 15 highly resistant s trains showed ofloxacin MICs of >4 mu g/ml and zone diameters of <13 m m. When tested with 5-mu g ciprofloxacin disks, the corresponding valu es for resistance and high-level resistance of these QRNG strains were <25 mm (MICs of >0.5 mu g/ml) and <15 mm (MICs of >2 mu g/ml), respec tively. Six strains for which ofloxacin MICs were greater than or equa l to 8 mu g/ml showed no zones at all with both 5-mu g ofloxacin and 5 -mu g ciprofloxacin disks. These QRNG strains are now firmly establish ed in the Southeast Asia region, and it is important for clinical labo ratories to recognize these clinically resistant strains and to monito r their spread.