Chlamydia trachomatis
Chlamydial infections
How is the infection transmitted?
The risk of infection with C. trachomatis from person-to-person is similar to that of gonorrhea, through sexual intercourse or oral sex. Men are more efficient in transmitting the bacterium to their female partners with spread 40-64% of the time, whereas women transmit the infection to their male partner 21-35% of the time. It can also be passed to the eye by a hand moistened with infected secretions. The bacterium can be transmitted during anal intercourse causing proctitis (inflammation of the rectum). It can also be passed from mother to her newborn child during birth, causing eye infection (conjunctivitis) or pneumonia.
What are the clinical signs and symptoms of chlamydial infection?
Most infections in females (60-80%) are asymptomatic, but the disease spectrum includes mucopurulent cervicitis, endometritis, salpingitis, the urethral syndrome, proctitis, post-abortal pelvic sepsis and perihepatitis. In numerous case-control and cohort studies chlamydial infection has been associated with the long-term complications of pelvic inflammatory disease, infertility and ectopic pregnancy. Serologic studies suggest that 64% or more of tubal infertility and 42% of ectopic pregnancies are attributable to chlamydial infection. Screening in different female populations in Canada have shown carrier rates of 1% to 25%. In Canada the women at highest risk for chlamydial infection are those who are sexually active and aged 15-19 years, followed by 20-25 years. Other factors associated with increased risk of infection include: intercourse with 2 or more partners per year or a new partner in the preceding year, low socioeconomic class, use of non barrier contraception, intermenstrual bleeding, cervical friability and purulent discharge on examination. Infection rates in pregnant women range from 5% to 25%. In prospective cohort studies, 11% to 44% of infants born to mothers infected with chlamydia developed conjunctivitis and 11-20% developed pneumonia during the first year of life. In males, the spectrum of disease due to C. trachomatis includes urethritis, epididymitis, prostatitis and occasionally proctitis or proctocolitis via homosexual transmission. Up to 50% of reported cases of non-gonococcal urethritis and 31% of cases of acute epididymitis are due to C. trachomatis. One percent to 21% of all men may be asymptomatic carriers and act as a reservoir for spread. Younger age, multiple sexual partners in the preceding year, and a history of gonorrhea in the past year are associated with increased likelihood of chlamydial infections in males.
How we can test C. trachomatis infections?
There is no simple, inexpensive laboratory test for diagnosing C. trachomatis infections, and different anatomical sites require different screening tests. In adult females, examination with a speculum and endocervical swabs are the appropriate methods. In prepubertal females, the immature vagina is the genital site of infection with C. trachomatis and N. gonorrhea. Thus, a speculum examination to obtain a cervical specimen is both unnecessary and potentially traumatic. Cervical swab for chlamydial culture has an estimated sensitivity of 75% to 90%, and a specificity of 100% but test time is 2-3 days. Cotton tipped aluminum and rayon tipped plastic swabs are superior to calcium alginate or cotton tipped wooden swabs for maximum yield of culture. This mode of diagnosis of C. trachomatis is expensive and time consuming, and requires technical expertise unavailable to most clinical laboratories. Cytologic testing using Giemsa or other methods is 95-100% sensitive for detecting conjunctivitis, but has low sensitivity for diagnosis of genital infections. Direct fluorescent antibody (DFA) testing using fluorescein-conjugated monoclonal antibodies and enzyme-linked immuno-assays (EIA) are the most widely used non-culture techniques for diagnosing cervical infections in clinical practice. DFA test time ranges from 15 minutes to 1 hour while EIA requires from 3-5 hours. They are not recommended for use on throat and rectal specimens from sexually abused children because chlamydia may cross react with bacterial flora giving false positive results. DFA sensitivity is 70-100% and specificity is 85-98% when compared to culture of cervical and urethral specimens in women. The sensitivity and positive predictive value of DFA decrease significantly as the prevalence of chlamydia in the population decreases. EIA has a sensitivity of 67-98% for cervical infections and specificity can be increased from 85% to almost 100% by the use of confirmatory blocking antibody assays. In men, C. trachomatis infections have traditionally been diagnosed by culture, DFA or EIA on urethral swabs. However, in contrast to women, testing of first void urine (FVU) specimens gives a yield that approaches that of urethral swabs. This represents a non-invasive alternative for chlamydial screening. Polymerase chain reaction (PCR) testing of cervical specimens in women and FVU specimens in men is 95-100% sensitive and almost 100% specific and its use may become more widespread but is currently limited by high cost. Serological testing for C. trachomatis, through the detection of various specific antibodies, is today an effective and highly claimed option. New and refined technologies apply the immunomarkers IgM, IgA and IgG to characterize the presence and stage of infection. Specific IgM is indicative of acute chlamydial infections. Absence does not, however, preclude the presence of on-going infection, especially in recurrent and chronic cases. The use of specific IgA as marker for active chlamydial infection has been shown to have an important role because of its short half life time, while persisting as long as antigenic stimulation exists. IgA is, moreover, suitable for post therapy follow-up. IgG is a marker for chlamydial positive immune response either current, chronic or past infections. Serological cross-reactions occur among the different species of chlamydia. Most of the serological diagnostic assays for chlamydia use either purified elementary bodies (microimmunofluorecence, MIF and ELISA tests), lipopolysaccharide or purified major outer membrane protein (ELISA tests) as antigens.
Genus specific epitopes are present in all the above antigens, therefore, low species specificity is observed. Moreover, large proportion of the population has been exposed to Chlamydophila pneumoniae (with no clinical signs) and thus, the prevalence of anti-chlamydia antibodies is very high. Therefore, the differentiation between C. pneumoniae and C. trachomatis specific antibodies using conventional serological screening tests (MIF, ELISA, EIA etc.) could be deficient. If necessary, PCR can be used to distinguish C. trachomatis infection from infection with other chlamydial species.
What is the treatment for C. trachomatis infections?
Tetracyclines are the drugs of choice for treatment of C. trachomatis infections in non-pregnant females and in males. The recommended dosage is 500 mg by mouth, four times a day for 7 days or doxycycline 100 mg by mouth, two times a day for 7 days. Traditionally, erythromycin 500 mg by mouth, four times a day for 7 days has been recommended for pregnant women and for those in whom tetracycline is contraindicated. Erythromycin is curative in 90% or more of patients who are able to take it. The major drawback of the 2 g dose is the high incidence of gastrointestinal side effects. Amoxicillin 500 mg by mouth, three times a day for 7 days was shown in a recent double-blind randomized trial to be equal in efficacy to erythromycin, but with fewer dropouts due to side effects. More recently, introduction of azithromycin has raised the prospect of single dose therapy. In prospective studies, a single 1 g dose of oral azithromycin was as effective as 100 mg of doxycycline given twice a day for 7 days in eradicating uncomplicated urogenital C. trachomatis infections in men and women. Side-effects (mainly gastrointestinal) were mild and of equal frequency in both treatment groups. Ofloxacin 300 mg twice a day for 7 days is also efficacious for treatment of uncomplicated infections in non-pregnant women, but is expensive for first line usage. A repeat chlamydia test should be taken 2 weeks after completion of antibiotic therapy. Safe sex practices should be reviewed and all sexual contacts should be tested, treated and found to be negative. Sexual relations should not be restarted until all of these are done. It is highly recommend that serology for HIV, hepatitis B, syphilis be taken at 3 months.
Costs and Economic Evaluations
Chlamydial infections are estimated to cost over U.S. $2.2 billion a year in the U.S. Infections in women account for over 79% of this cost. Economic evaluations support chlamydial screening of asymptomatic persons under specific conditions. A decision analysis was used to estimate the clinical and economic implications of testing for cervical infection caused by C. trachomatis in asymptomatic women during routine gynecologic visits. A strategy of no routine testing was compared with one involving routine cultures or use of non-culture tests (DFA or EIA). It was concluded that the use of the non-culture tests would reduce overall costs if the prevalence of infection was 7% or greater, and routine cultures if the prevalence was 14% or more.
What can be done to prevent/control C. trachomatis infection?
- The use of condoms during vaginal and anal intercourse.
- Sexual practices other than intercourse carry less risk of transmitting chlamydia.
- Because chlamydia can infect the eyes, care must be taken to avoid spreading sexual fluids into them.
- Where infection has occurred, it is important to avoid sexual contact involving the genitals during the course of treatment until a negative test result is obtained. This will aid healing and prevent transmission.
- If your sexual partner has any discharge, testing for chlamydia should be requested and you too should be checked.
- Where there has been unprotected intercourse and one or more of the following exist:
- Change of sexual partners in previous 2 months
- More than one sexual partner
- Partner has other sexual partners
- If you are under 25 years and there has been unprotected intercourse, there is a greater likelihood that one or more of the above factors will exist
Many physicians believe that all partners should be treated whether or not they have a positive test for chlamydia. Since gonorrhea and even syphilis are often transmitted with chlamydia testing for these STDs should also be performed prior to treatment of chlamydia.
