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Time to clearance of Chlamydia trachomatis ribosomal RNA in women treated for chlamydial infection

Cybèle A. Renault A B , Dennis M. Israelski A B , Vivian Levy A B E , Bruce K. Fujikawa B , Timothy A. Kellogg C and Jeffrey D. Klausner C D

A Stanford University School of Medicine, Division of Infectious Diseases and Geographic Medicine, 300 Pasteur Drive, Grant Building, Stanford, CA 94305-5107, USA.

B San Mateo County Health System, 222 West 39th Avenue, San Mateo, CA 94403, USA.

C San Francisco Department of Public Health, STD Prevention and Control Services, 1360 Mission Street, Suite 401, San Francisco, CA 94103, USA.

D Department of Medicine, University of California, 505 Parnassus Avenue, San Francisco, CA 94122, USA.

E Corresponding author. Email:

Sexual Health 8(1) 69-73
Submitted: 9 March 2010  Accepted: 24 May 2010   Published: 24 January 2011


Background: The dynamics of chlamydia clearance after treatment administration for chlamydial urogenital infection are unknown. We estimated the time to clearance of Chlamydia trachomatis (CT) ribosomal RNA (rRNA) after administration of azithromycin for cervical chlamydial infection using APTIMA Combo 2 (Gen-Probe, Inc., San Diego, CA, USA). Methods: A total of 115 women diagnosed with urogenital chlamydial infection, defined as a positive APTIMA urine or endocervical specimen, were enrolled in the present study. Vaginal swabs on the day of treatment (Day 0) and on Days 3, 7, 10 and 14 after treatment with 1 g of azithromycin were self-obtained by participants. Specimens were tested in a single laboratory. Our analysis was limited to women who were CT-confirmed by vaginal swab at baseline, who returned all follow-up swabs, and who reported sexual abstinence during the follow-up period (n = 61). Results: Among 61 participants, 48 (79%) had a negative APTIMA at Day 14. Subjects with a negative APTIMA at each time-point were as follows: 0/61 (0%) on Day 0, 7/61 (12%) on Day 3, 28/61 (46%) on Day 7, 40/61 (66%) on Day 10, and 48/61 (79%) on Day 14. Multiple linear regression analysis predicted time to clearance at 17 days (95% confidence interval, 16–18 days) after administration of azithromycin. Seventeen of the 94 participants (18.1%) who screened positive for chlamydia had a negative vaginal swab on Day 0, indicating possible spontaneous clearance of CT. Conclusions: After treatment, CT rRNA declined with time. As rRNA was still detectable in 21% of the women 14 days after treatment, APTIMA should not be used as a test-of-cure in the 14-day period following azithromycin administration.

Additional keywords: APTIMA, test-of-cure, transcription-mediated amplification.


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