STD- The Most Common Infections

Because the goal of this section is to deal with the closely defined STDs, as opposed to HIV and hepatitis B, stress is put on the former only. Although new cases of syphilis are estimated annually to be 12 million cases worldwide, with particularly high rates observed in teenagers, this feared and famousinfamous classic STD has not been taken into consideration in this section.

Concerning Spirochaeta pallidum-caused symptoms, stages of disease and sequelae, as well as diagnostic and treatment, see the published reviews.


Chlamydia trachomatis; obligate intracellular parasite. Incubation period: 7 - 21 days.

Epidemiology. Chlamydial infections are by far the most frequent bacterial STDs worldwide. However, because of inadequate diagnostic facilities, the incidence of chlamydiae is heavily underestimated. From the few countries that were able to do intensive testing, an initial increase in incidence was reported, which recently has been followed by a reduction as a result of treatment. But it must be emphasized that in adolescents the highest infection rates with C. trachomatis are to be found concurrently.

From the given and estimated rates of chlamydial infections in females up to 25 years of age, probably an average of 6% are infected asymptomatically compared to more than 10% of sexually active adolescents. Obviously, chlamydiae are found more often in girls or women suffering from discomfort and discharge (

table 6).

Current data also show females who suffer from chlamydial cervicitis, with up to 30% of their male partners carrying positive urethral cultures. Nevertheless, more than 80% of these cases occur asymptomatically. Most likely these youngsters are the main source for the spread of chlamydial infection to young females, with other males then becoming infected.

Symptoms, Diseases and Sequelae. Chlamydial infections in girls often occur asymptomatically, but some non-specific discharge may be observed.

Chlamydial infections of the cervix may progress to the upper genital tract causing PID, endometritis and perihepatitis (Fitz-Hugh-Curtis syndrome). Though symptoms of PID can be mild, the infection itself tends to result in severe tubal scarring causing infertility, ectopic pregnancy and chronic pelvic pain. A sexually active 15-year-old girl, for example, has a 1:8 chance of developing PID as compared with 1:80 for a 24-year-old woman.

Associated with Chlamydia in more than 80% of the cases are urethritis, conjunctivitis, and arthritis (Reiter’s syndrome) as evidence of past or concurrent infection.

Diagnosis. Significant advances in the diagnosis of STDs have been made by the development of independent culture tests for identification of C. trachomatis, which may also include N. gonorrhoeae, HPV and HSV (

table 7).

Recently, urine-specimen-based DNA amplification techniques, including polymerase chain reaction (PCR) and ligase chain reaction (LCR), show sensitivities of about 90% and more. These advanced techniques are suitable for both symptomatic men and women and for screening in asymptomatic individuals.

Furthermore, many of these techniques permit testing for chlamydiae as well as N. gonorrhoeae with sensitivities of more than 95%.

Based on smears obtained from the cervix or urethra, the diagnosis of chlamydiae from cell cultures, e.g., McCoy cells, requires more time and is 80% less sensitive than the PCR/LCR methods. Identification tests of Chlamydia antibodies by immunofluorescence, immunoperoxidase testing or enzyme immunoassay are not specific for C. trachomatis only.

Because of the difficulty of distinguishing symptoms of chlamydial infection, screening should be performed every 6 months for sexually active teenagers and particularly for those with urethritis symptoms, bleeding disturbances or frequent partner changes.

Treatment. Various options for antibiotic therapy are available for uncomplicated Chlamydia infection (

table 8). Single-dose orally administered azithromycin 1 g is well accepted by adolescents compared with doxycycline 100 mg twice a day for 1 week.

Adolescents suffering from PID should be admitted to the hospital to start intravenous antibiotic therapy because of the risk of noncompliance and concerns for serious sequelae (

table 9). Because of the high risk of simultaneous asymptomatic infection, sexual partners of infected girls should be treated as well in all cases. No resistance of C. trachomatis to tetracycline or erythromycin has yet been found.

After treatment, tests should be done 21 - 28 days following azithromycin treatment and 7 - 14 days following treatment with other antibiotics.

Provided by ArmMed Media
Revision date: July 9, 2011
Last revised: by Sebastian Scheller, MD, ScD