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Sexually transmitted diseases (STDs) describe a range of infections acquired through sexual contact and have a major impact on public health and the utilization of health care resources. STDs are associated with symptomatic disease, infertility, and deleterious effects on pregnancy and childbirth, among other complications. Four STDs will be reviewed in this chapter: chlamydia, gonorrhea, genital herpes, and syphilis.


Chlamydial genital infection is caused by Chlamydia trachomatis, an obligate intracellular pathogen and the most common bacterium responsible for STDs. Infection is transmissible through vaginal, anal, or oral sex. Chlamydia can manifest as cervicitis in women and urethritis in men; however, asymptomatic infection is common, occurring in up to 70% of women and 50% of men. In symptomatic disease, women present with mucopurulent vaginal discharge, postcoital bleeding, and urethral infection. Symptoms in men include dysuria and urethral discharge. Without appropriate and timely treatment, complications such as pelvic inflammatory disease (PID), ectopic pregnancy, premature delivery, and infertility can result.

Testing methods for diagnosis of chlamydia include cell culture, antigen-based tests, molecular methods such as nucleic acid hybridization (deoxyribonucleic acid [DNA] probing), and nucleic acid amplification tests (NAATs). NAATs are recommended for diagnosing chlamydial genital infection due to high sensitivity and specificity.


Gonorrhea is caused by Neisseria gonorrhoeae, a gram-negative diplococcus, and is transmissible through contact with genitals, mouth, or anus. After contact is made, the organism attaches to mucosal epithelium causing a strong neutrophil response with pus production. Gonococcal infection causes cervicitis in women and urethritis in men. In men, symptoms include dysuria and urethral discharge which becomes purulent within days. Because of the early presentation and discomfort associated with symptoms in men, treatment is sought early enough to prevent complications. Women are asymptomatic or have minor symptoms. Symptoms occur within 10 days in those who develop them and include vaginal discharge, dysuria, and vaginal bleeding (sometimes postcoital). Asymptomatic infection in women can lead to PID, ectopic pregnancy, tubal scarring, and infertility. In both men and women, gonorrhea can cause increased susceptibility to and transmission of human immunodeficiency virus (HIV) infection.

In symptomatic men, a urethral specimen Gram stain showing neutrophils and gram-negative diplococci can be considered diagnostic, but a negative Gram stain is not sufficient to rule out infection in asymptomatic men. Other diagnostic tests for gonococcal urethritis and cervicitis include culture, nucleic acid hybridization, and NAATs. NAATs offer the widest range of specimen types for diagnosis. Nonculture diagnostic tests cannot provide antibiotic susceptibility results, which may be necessary in cases of infection that persists after treatment.

Genital Herpes

Genital herpes is a chronic, lifelong viral infection due to double-stranded DNA viruses of the Herpesviridae family. Two types of virus cause clinical disease: herpes simplex virus-1 (HSV-1) and herpes simplex virus-2 (HSV-2). While most genital herpes is ...

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