Chapter 78 – Bacterial Sexually Transmitted Infections (STIs): A Clinical Overview*

Bacterial agents of sexually transmitted diseases (STDs) constitute a major public health burden in both industrialized and developed countries. They include Neisseria gonorrheae, the causative agent of gonorrhoea; Chlamydia trachomatis, which causes chlamydial infections and their sequelae; Treponema pallidum, the aetiologic agent of syphilis; Klebsiella granulomatis (formerly called Calymmatobacterium granulomatis), which causes granuloma inguinale (donovanosis); Haemophilus ducreyi, the aetiologic agent of chancroid; and some species of Mycoplasma and Ureaplasma that are occasional causes of consequential sexually transmitted infections (STIs). Bacterial STD syndromes range from serious and/or life-threatening conditions, such as syphilis, to debilitating syndromes with long-term consequences, including pelvic inflammatory disease, endometritis, ectopic pregnancy, and infertility; in addition, less serious pathological presentations such as self-limiting urethritis, cervicitis and fever are associated with bacterial STIs. Interestingly, three of the diseases that are subject in the USA to mandatory reporting to public health agencies are caused by bacterial STD agents: gonorrhoea, chlamydia and syphilis. In general, the pathogeneses of bacterial STDs include both microbial factors and host inflammatory reactions to the infection. As common features, bacterial STDs are more prevalent among adolescents than older adults, suggesting that immune resistance may build up in adults over time; they are treatable with reliable antimicrobials if detected early; they may have irreversible sequelae; they can increase the risk of viral STIs, such as human papillomavirus (HPV) and human immunodeficiency virus (HIV); their transmission is usually via direct genital mucosal contact; and there are no human vaccines currently available. This chapter presents current information on the burden of infection, aetiological agents, clinical presentation and features, microbiology, pathogenesis (including microbial and host contribution to disease onset and progression), diagnosis, treatment, and state-of-the-art approaches to prevention and control of chlamydia, gonorrhoea, syphilis, chancroid and mycoplasmal diseases. For the purpose of providing a clinically relevant overview of these common bacterial STDs, we have referenced and summarized information from the current CDC STD Treatment Guidelines and other recent reviews.