Emerging evidence suggests that a seven-day course of doxycycline may be more appropriate than one dose of azithromycin as a first-line treatment for chlamydial infection. Although a seven-day course is less convenient for patients, increased use of doxycycline may help reduce the high rates of chlamydia transmission and reinfection.
Throat swabs should be considered for chlamydia and gonorrhea due to increasing rates of pharyngeal gonorrhea infection, particularly in men who have sex with men.
The highest rates of Chlamydia trachomatis infection are reported in young people ; 82% of cases reported to the New Zealand Institute of Environmental Science and Research (ESR) between 2013 and 2017 were in people aged 15 to 29 years. Data suggests that by age 38, one in three women and one in five men in New Zealand will acquire a chlamydia infection at least once.
Reinfection is common
Chlamydia reinfection rates are high. For example, data from laboratory testing services covering the Wellington region, collected between 2012 and 2015, found that 18% of people who tested positive for chlamydia or gonorrhea tested positive within the next six weeks. . to six months.
Untreated rectal chlamydia in women is likely to be a major source of reinfection.
Men who have sex with men (MSM) have generally been the focus of research for rectal chlamydia infection. However, data from studies conducted over the past ten years show that rectal chlamydia in women is likely to be an overlooked source of reinfection.
Many women with genital chlamydia also have rectal infection: a meta-analysis of 14 studies, conducted in the UK, US, Canada, Australia and Europe, found that, on average, 68% of women with genital chlamydia infection They were also positive for rectal infection. In contrast, rectal infection in the absence of genital infection is uncommon; Approximately 2% of women in these studies tested positive for rectal but not genital infection.
Most people with rectal chlamydia infection are asymptomatic : at least 90% of women and 70% of MSM with rectal chlamydia infection are asymptomatic.
In women, rectal infection does not depend on sexual practices: studies have found no association between rectal chlamydia infection in women and whether they have had anal sex. This suggests that rectal infection arises in many women due to spread of genital infection to the rectum, rather than transmission through sexual practices.
Doxycycline is most effective in treating rectal chlamydia
A single dose of azithromycin is currently the recommended first-line antibiotic regimen for the treatment of genital chlamydial infection and is effective in 94% of patients. An alternative treatment is a seven-day course of doxycycline, which is effective in 97% of patients with genital chlamydial infection.
Since both regimens offer similar efficacy and azithromycin is a single dose that is often administered in the clinic at the time of the appointment, it has typically been used as a first-line treatment for patients with genital chlamydial infection and for the treatment of sexual contacts.
However, azithromycin is less effective in treating rectal chlamydia infection than doxycycline. A meta-analysis reported that the average efficacy of one dose of azithromycin for treating rectal chlamydia was 83%, compared to >99% over a seven-day course. of doxycycline.
The use of azithromycin can cause resistance in other STIs
Mycoplasma genitalium is an emerging cause of STIs such as persistent urethritis in men and cervicitis and pelvic inflammatory disease in women. Data suggest that the use of single-dose azithromycin regimens may lead to the emergence of resistance in M. genitalium . Therefore, since this organism shares similar sites of infection with chlamydia, reducing the use of azithromycin as a first-line treatment for chlamydial infection may help prevent resistance in M. genitalium .
What does this evidence mean for the treatment of chlamydia infection in women?
Emerging evidence that asymptomatic rectal chlamydial infection is common in women and less responsive than genital infection to a dose of azithromycin suggests that this may be an important cause of recurrent or persistent chlamydial infection.
Consider prescribing doxycycline, 100 mg twice daily for seven days , first line: This regimen is estimated to be effective for approximately 97% of women with genital or rectal chlamydia.
The new evidence creates a dilemma for testing in women: Currently, anorectal swabs are recommended for women who report having had anal sex. Additionally, current guidelines recommend repeat testing to cure patients with rectal chlamydia.
However, the data suggest that reported sexual practices are not a useful guide in deciding whether a rectal swab is necessary. Collecting rectal swabs for all patients would increase the invasiveness of testing and result in a large number of additional tests.
Furthermore, if all women who tested positive for rectal infection were asked to return for a cure test, this would create an additional burden on patients due to the time and cost of returning.
A pragmatic approach would be:
- Collect genital swabs*
- Suppose that women who test positive for genital chlamydia may also have rectal infection.
- Prescribe doxycycline, 100 mg twice daily for seven days
Cure testing, using genital and anorectal swabs, could be reserved for patients at high risk of reinfection or consequences of reinfection, such as if sexual contacts have not been treated, if insertion of an intrauterine device is planned, or there are concerns regarding to adherence to a seven-day regimen.
* A vulvovaginal NAAT swab, either collected by herself or by a doctor (usually to screen for chlamydia and gonorrhea) and, in addition, if symptomatic, a high vaginal culture swab collected by the doctor and an endocervical swab for culture of gonorrhea (if available).
To reduce reinfection, trace and treat sexual contacts: Sexual contacts from the previous three months should be contacted, treated empirically , preferably with a seven-day course of doxycycline, and offered STI testing.
What does this evidence mean for the treatment of chlamydia infection in men?
Testing recommendations for men who have sex with men (MSM) have not changed: routine testing for rectal and pharyngeal chlamydia and gonorrhea infection as part of a sexual health check remains appropriate in this high-risk population. Rectal chlamydial infection is more common than urethral infection in MSM and is usually asymptomatic and may increase the risk of HIV transmission.
In addition to rectal swabs, it is recommended to collect swabs for routine testing for pharyngeal chlamydia or gonorrhea infection in MSM. For patients with positive rectal or pharyngeal test results, test-of-cure is recommended. Doxycycline is also the recommended treatment for rectal chlamydia in men.
For heterosexual males with urethral chlamydia, it is also likely preferable to prescribe a seven-day course of doxycycline, as azithromycin use may contribute to the development of resistance in M. genitalium , a cause of urethritis. Unlike heterosexual women, there is currently no data to suggest that heterosexual men with genital chlamydia have high rates of rectal infection.
Gonorrhea rates are increasing, including pharyngeal infection rates
The current national (NZ) rate of gonorrhea infection is approximately 100 cases per 100,000 population, with higher rates in men than women. The incidence has increased in recent years, with a higher proportion of positive throat swab tests for gonorrhea in men. A key reason for rising gonorrhea rates, particularly in large urban areas, is likely to be increased transmission among MSM.
Pharyngeal infection is usually asymptomatic and is thought to play an important role in the development of antibiotic resistance in N. gonorrhoea in the pharynx.
In men, genital gonorrhea infection is usually symptomatic.
Testing for asymptomatic infection is not necessary in heterosexual men, however, it should be offered at least annually as part of routine sexual health screening in MSM, due to the high rates of gonorrhea in this population. Samples collected should include rectal and pharyngeal NAAT swabs and a first empty urine sample to screen for chlamydia and gonorrhea infection. Throat swab collection in heterosexual men may be appropriate if there is a high degree of suspicion, e.g. if a sexual contact has had a chlamydia or gonorrhea infection.
In women , testing for genital gonorrhea infection is recommended during a sexual health checkup, as up to 80% of women with genital gonorrhea infection are asymptomatic . Collection of throat swabs may be appropriate if there is a high degree of suspicion, e.g. Eg. if a sexual contact has had a chlamydia or gonorrhea infection.
The recommended first-line treatment for gonorrhea infection is the same for genital, rectal, or pharyngeal infections: ceftriaxone , 500 mg by intramuscular injection, and azithromycin , 1 g.
The recommended first-line treatment for pharyngeal chlamydia infection is the same as for rectal chlamydia: doxycycline, 100 mg twice daily, for seven days.
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