The susceptibility of Neisseria gonorrhoeae strains to different cephalosporins and penicillin G depends on the auxotype.

The relatively broad range of minimum inhibitory concentrations (MICs) of different cephalosporins and penicillin G with Neisseria gonorrhoeae results from the differing susceptibility of various subsets, i.e. auxotypes. While prototrophic and proline-dependent strains are especially resistant (p less than or equal to 0.001), AHU strains are especially susceptible. The bimodality of MIC values with penicillin G and the older cephalosporins, cephalothin and cefazoline, results from quite a big subset of relatively resistant prototrophic strains. As the newer cephalosporins from generation (e.g. cefotiam) to generation (e.g. cefmenoxime and ceftizoxime) tend to have less special problems with these strains, the general distribution of MIC values changes to monomodality.