Activity of cefixime against Neisseria gonorrhoeae

Background In most gonococcal populations, penicillin-resistant strains have increased dramatically and penicillin can no longer be recommended for the treatment of gonorrhoea. Cefixime is the first oral third generation cephalosporin and represents an alternative therapeutical approach. Objective To evaluate the in vitro activity of cefixime against a gonococcal population in Germany. Material 203 Neisseria gonorrhoeae strains, isolated in the area of Heidelberg between 1986 and 1990, including 14 penicillinase-producing Neisseria gonorrhoeae (PPNG) strains and five strains with chromosomally mediated penicillin resistance (CMPR). Methods Determination of minimal inhibitory concentration (MIC) of cefixime was performed by standard agar dilution technique. Auxotype/serovar (A/S) classification was performed by using Neisseria defined agar and 12 gonococcal outer membrane porin specific monoclonal antibodies in a coagglutination assay. Results The MIC range reached from 0.00025 μg/ml to 0.125 μg/ml cefixime. For both penicillin sensitive- and penicillin-resistant strains, the geometric mean MIC was 0.0048 μg/ml, MIC 50 0.002 μg/ml and MIC 90 0.008 μg/ml. Among gonococcal strains with an MIC of 0.001 μg/ml cefixime strains belonging to A/S class (P)AH(U)/1A-1/2 were significantly more frequent (p < 0.0001) than among strains having an MIC of > 0.001 μg/ml. Conclusion Cefixime showed very high antimicrobial activity against Neisseria gonorrhoeae. All tested gonococcal strains were susceptible to cefixime. The A/S class composition of a tested gonococcal population influences very strongly the range of MICs.