Phenotypic antimicrobial susceptibility testing of Chlamydia trachomatis isolates from patients with persistent or successfully treated infections.

Objectives: Antimicrobial susceptibility data for Chlamydia trachomatis are lacking. Methodologies for susceptibility testing in C. trachomatis are not well-defined, standardized or performed routinely owing to its intracellular growth requirements. We sought to develop an assay for the in vitro susceptibility testing of C. trachomatis isolates from two patient cohorts with different clinical outcomes. Methods: Twenty-four clinical isolates (11 from persistently infected and 13 from successfully treated patients) were overlaid with media containing two-fold serial dilutions of azithromycin or doxycycline. After incubation, aliquots were removed from the stock inoculum (SI) and each antimicrobial concentration for total RNA extraction, complementary DNA generation and real-time PCR. The MIC was defined as the lowest antimicrobial concentration where a 95% reduction in transcription was evident in comparison with the SI for each isolate. Results: MICs of azithromycin were comparable for isolates from the two patient groups (82% ≤ 0.25 mg/L for persistently infected and 100% ≤ 0.25 mg/L for successfully treated patients). Doxycycline MICs were at least two-fold lower for isolates from the successfully treated patients (53.9% ≤ 0.064 mg/L) than for the persistently infected patients (100% ≥ 0.125 mg/L) (P = 0.006, Fisher's exact test). Overall, 96% of isolates gave reproducible MICs when re-tested. Conclusions: A reproducible assay was developed for antimicrobial susceptibility testing of C. trachomatis. MICs of azithromycin were generally comparable for the two different patient groups. MICs of doxycycline were significantly higher in the persistently infected patients. However, interpretation of elevated MICs in C. trachomatis is extremely challenging in the absence of breakpoints, or wild-type and treatment failure MIC distribution data.

What is the appropriate treatment for the management of rectal Chlamydia trachomatis in men and women?

BACKGROUND: There is no UK guidance specifically for the management of rectal Chlamydia trachomatis yet there is documented treatment failure with single-dose azithromycin suggesting that test of cure (TOC) and alternative treatment may be needed. OBJECTIVES: To evaluate the efficacy of single-dose azithromycin compared with 1 week of doxycycline in the treatment of rectal C trachomatis. METHODS: Data were collected prospectively on all patients diagnosed with rectal C trachomatis who received azithromycin 1 g stat between 1 January and 30 June 2010 and between 1 October 2010 and 31 March 2011 following a local change in treatment protocol to 1 week of doxycycline 100 mg twice a day. Information was collected on gender, concurrent sexually transmitted infections, treatment received, re-infection risk, re-treatment and TOC at 6 weeks. RESULTS: 11 patients (26.2%) had a positive TOC following treatment with stat azithromycin. The risk of re-infection was excluded in two, identifying nine of the 11 (81.8%) as treatment failures. Two patients had a positive TOC following treatment with 1 week of doxycycline, both were found to have a risk of re-infection. There was a significantly higher treatment failure rate in patients receiving azithromycin (p=0.0025). CONCLUSIONS: A higher treatment failure rate was found following azithromycin for rectal C trachomatis than previously published. If azithromycin is used for treatment of rectal C trachomatis, TOC may be required or alternative treatment with doxycycline may be preferable, but further data are required.

Sexual health care of HIV-positive patients: an audit of a local service.

The sexual health care of 175 HIV-positive patients attending the two HIV clinics at Barts and the London NHS Trust was audited for the first time. The audit standard was that 100% of patients should be in receipt of a sexual health screen within six months of their first HIV out-patient appointment. Overall, 44.5% of patients had a sexual health screen, of which 46 (60.5%) were diagnosed with a sexually transmitted infection. Those screened were younger than those who were not. Five factors were identified which were significantly associated with not having a genitourinary screen performed; site of HIV care, setting of HIV diagnosis, stage of HIV disease, specialty of HIV physician and whether a screen was recommended by the HIV physician. A number of recommendations have been implemented to improve the uptake of sexual health screening amongst HIV-positive patients.