Abstract: Objective To detect and compare the in vitro activities of several antimicrobial agents against isolates of Chlamydia trachomatis (Ct) cultured from the genitalia in the past several years.Methods Strains of Ct cultured in 1997,1999,2001,2003 and 2005 were selected.The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of 7 antibacterial agents,including erythromycin,minocycline,azithromycin,clarithromycin,levo-ofloxacin,sparfloxacin and moxifloxacin,against these strains were assessed in McCoy cell culture.Results The MIC₉₀ and MBC₉₀ of the these drugs increased from 1997 to 2005,especially those of levofloxacin,which increased from 0.063 mg/L to 1 mg/L and from 0.063 mg/L to 4 mg/L,respectively.The MIC₉₀ and MBC₉₀ of clarithromycin,sparfloxacin and moxifloxacin against clinical isolates of Ct in 2005 were relatively low,with the MBC₉₀ of 0.25 mg/L,0.125 mg/L and 0.063 mg/L respectively.Conclusions In the past several years,the in vitro effectiveness of these antimicrobial agents against clinical Ct isolates have gradually decreased;clarithromycin,sparfloxacin and moxifloxacin showed good in vitro activity against the most recent isolates of genital Ct.

Key words: Chlamydia trachomatis, Microbial sensitivity tests, Macrolides, Minocycline, Quniolones