Activity of thiamphenicol against Chlamydia trachomatis and Neisseria gonorrhoeae

The in-vitro activity of thiamphenicol against Neisseria gonorrhoeae was compared with that of penicillin. A total of 267 isolates were tested. All strains were inhibited by less than or equal to 4.0 micrograms of thiamphenicol/ml. However, the minimal inhibitory concentration of thiamphenicol was fourfold higher (MIC90 = 2.0 micrograms/ml) for beta-lactamase-producing strains or those moderately resistant to penicillin than for penicillin-sensitive strains (MIC90 = 0.5 micrograms/ml). The MIC of thiamphenicol for Chlamydia trachomatis was determined for a control strain and for 15 recent clinical isolates. The MIC90 for thiamphenicol was 1.0 micrograms/ml, as compared with a MIC90 of oxytetracycline of 0.12 micrograms/ml against the same isolates.