title: Association of the in vitro susceptibility of clinical isolates of chlamydia trachomatis with serovar and duration of antibiotic exposure.
abstract: BACKGROUND
  The presence of persistent Chlamydia trachomatis infection after treatment does not always correlate with in vitro susceptibility testing.
  
  
  METHODS
  The in vitro minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of azithromycin, clarithromycin, roxithromycin, doxycycline, tetracycline, ofloxacin, and penicillin were tested against 61 clinical isolates of C. trachomatis on 6 serovars, and the MIC/MBC of azithromycin and ofloxacin at different points in time after antibiotic administration to infected cultures.
  
  
  RESULTS
  Of the 7 antibiotics tested, clarithromycin showed the greatest activity against C. trachomatis isolates with MIC90 of 0.032 μg/mL and MBC90 of 0.064 μg/mL, followed by doxycycline with MIC90 0.064 μg/mL and MBC90 0.064 μg/mL, and azithromycin with MIC90 0.160 μg/mL and MBC90 0.320 μg/mL. Azithromycin had roughly the same MIC50 values (0.08 μg/mL) as the other serovars isolates tested, and other antibiotics showed a 2- to 4-fold difference in MICs50 between serovars. In addition, an increase in the azithromyin MIC was observed by 8 hours and the ofloxacin MIC by 16 hours. At 24 hours, the azithromycin MICs were greater than 40 μg/mL and ofloxacin MICs were greater than 64 μg/mL.
  
  
  CONCLUSIONS
  The current data demonstrated that the antimicrobial susceptibility of C. trachomatis was influenced by both the serovar type and the duration of exposure to antibiotics in infected cultures.
authors: From the *Guangdong Provincial Dermatology Hospital/Guangdong Provincial Center for Skin Diseases and STD Control, Guangzhou, China; and †Xiangya School of Medicine, Central South University, Changsha, China.
authors: Heping
authors: H
authors: Zheng
authors: Yaohua
authors: Y
authors: Xue
authors: Shun
authors: S
authors: Bai
authors: Xiaolin
authors: X
authors: Qin
authors: Ping
authors: P
authors: Lu
authors: Bin
authors: B
authors: Yang
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017963:Azithromycin / Q000494:pharmacology; D002690:Chlamydia Infections / Q000188:drug therapy / Q000382:microbiology*; D002692:Chlamydia trachomatis / Q000187:drug effects / Q000302:isolation & purification*; D017291:Clarithromycin / Q000494:pharmacology; D004318:Doxycycline / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D005347:Fibroblasts / Q000187:drug effects / Q000382:microbiology*; D006801:Humans; D066298:In Vitro Techniques / Q000379:methods*; D051379:Mice; D008826:Microbial Sensitivity Tests; D065288:Serogroup
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin; D017291:Clarithromycin; D004318:Doxycycline