[In vitro activity of a new quinolone, NM 394, against Chlamydia trachomatis]

A study of antimicrobial susceptibility of Chlamydia trachomatis was performed with a new quinolone, NM 394 (Laboratoire Dr. Bouchara). Ten C. trachomatis strains of four different genovars (3G, 4E, 2D, IDv) were grown in confluent McCoy cells on coverslips in multidishes (24 wells). For each C. trachomatis strain, two multidishes were prepared, one for MIC, one for MBC. Three inoculum titrated from 100 to 10000 IFU/ml were inoculated into wells. After incubation 48 h at 37 degrees C, the cultures were fixed in methanol and examined for inclusions after staining with fluorescein-conjugated anti-Chlamydia antibody. The MIC was defined as the lowest antibiotic concentration at which no inclusion formation was observed. For the determination of MBC, the culture media was replaced with sucrose phosphate buffer (2SP) and the cultures were incubated without antibiotic for 48 h and stained. The MBC was the lowest antibiotic concentration at which no inclusion formation was observed after one passage without antibiotic. The increase of the inoculum from 10(3) to 10(5) IFU/ml did not affect significantly the activity of NM 394. All strains were inhibited by 16 mg/l of NM 394. The IC 50 and 90 were 2 and 8 mg/l respectively. The MIC and the MBC values were similar.