Porth's Essentials of Pathophysiology, 4e

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Sexually Transmitted Infections

C h a p t e r 4 1

an hour. 4,19 Because the organism resides in other uro- genital structures besides the vagina, systemic treatment is recommended. Metronidazole and tinidazole, which are the treatments of choice against anaerobic protozo- ans, can cure T. vaginalis . 19 Systemic treatment is pre- ferred over topical application to achieve adequate drug concentrations in nonvaginal sites. 19 Because the organ- ism responds to only one class of medication, mild drug resistance has been noted against metronidazole but not tinidazole. 24 Although metronidazole is considered safe for use during pregnancy, data on tinidazole use in preg- nancy are limited. Sexual partners should be treated to avoid reinfection, and abstinence is recommended until the full course of therapy is completed. Bacterial Vaginosis Bacterial vaginosis is a polymicrobial infection charac- terized by lack of hydrogen peroxide–producing lac- tobacilli and an overgrowth of anaerobic organisms. It is the most prevalent vaginal disorder in women of reproductive age. 2 Bacterial vaginosis is associated with multiple male or female sex partners, a new sex partner, lack of condom use, and douching. 4,22–24 Sexual activity is believed to be a catalyst rather than a primary mode of transmission, and endogenous factors may play a role in the development of symptoms. The predominant symptom of bacterial vaginosis is a thin, grayish-white discharge that has a foul, fishy odor. Burning, itching, and erythema usually are absent because the bacteria have only minimal inflammatory potential. Because of the lack of inflammation, the term vaginosis rather than vaginitis is used to describe the condition. The organisms associated with bacterial vaginosis may be carried asymptomatically by men and women. The pathogenesis of bacterial vaginosis remains poorly understood. It is a complex disorder character- ized by a shift in the vaginal flora from one dominated by hydrogen peroxide–producing lactobacilli to one with greatly reduced numbers of Lactobacillus species and an overgrowth of facultative anaerobic organisms, including Gardnerella vaginalis , Mobiluncus species, and Mycoplasma hominis . 2,22,24 The massive overgrowth of vaginal anaerobes is associated with the production of proteolytic enzymes that break down vaginal amines, which become volatile and malodorous in a high pH. The amines are associated with increased vaginal secre- tions and squamous epithelial cell exfoliation, creating the typical discharge. In conditions of elevated pH, the vaginal anaerobes more efficiently adhere to the exfoli- ating epithelial cells, creating what are called clue cells (Fig. 41-4). In addition to causing bothersome symptoms, bac- terial vaginosis is associated with an increased risk of pelvic inflammatory disease (PID), adverse pregnancy outcomes including premature rupture of membranes, preterm labor, preterm birth, and postpartum endometri- tis linked to the organisms associated with bacterial vagi- nosis. Postoperative infections, including postabortion

usually requires a medical appointment to confirm the presence of vaginal candidiasis. Recurrent vulvovagi- nal candidiasis, defined as four or more mycologically confirmed episodes within 1 year, affects approximately 5% of women and is difficult to manage. Maintenance therapy with oral fluconazole often is required for long- term management of this problem. 16–18 Trichomoniasis Trichomoniasis affects an estimated 120million people in the United States and is the most prevalent nonviral sex- ually transmitted infection worldwide. 4 Trichomoniasis vaginalis infections are commonly associated with other STIs and are therefore a marker for high-risk sexual behavior. Although the infection is commonly transmit- ted by sexual contact, it can occur via fomites and the organism has been shown to survive in swimming pools and hot tubs. 2 The manifestations of infection with T. vaginalis, the causative agent of trichomoniasis, are primarily observed in women, and range from asymptomatic presentation to a copious, frothy, malodorous green or yellow dis- charge. 19–21 There often is erythema and edema of the affected mucosa, with occasional itching and irritation. Sometimes, small hemorrhagic punctations, called straw­ berry spots , appear on the cervix. Men can present with urethritis, prostatitis, and discharge, but most men are largely asymptomatic. 21 Trichomoniasis vaginalis is an anaerobic protozoan that is shaped like a turnip and has three or four ante- rior flagella (see Fig. 41-3B, C). Trichomonads can reside in the paraurethral glands of both sexes. This extracel- lular parasite feeds on the vaginal mucosa and ingests bacteria and leukocytes. Trichomonads attach easily to mucous membranes. It may reduce the chorioamnionic membrane strength and predispose pregnant women to premature rupture of membranes and premature birth. 19 Trichomoniasis vaginalis infection has emerged as a cofactor for HIV transmission. Potential mechanisms for increased susceptibility include recruitment of HIV tar- get cells, weakening of structural integrity of epithelial cells and their defense against HIV invasion, and creation of punctate microhemorrhages in mucosal genital tissue that serve as a portal of HIV entry. 19,20 Trichomonads may serve as vectors for the spread of other organisms, carrying pathogens attached to their surface into the fal- lopian tubes; infection has been associated with acute sal- pingitis and postpartum endometrial infection. 21 In men, it is a common cause of nongonococcal urethritis and is a risk factor for infertility, altering sperm motility and via- bility. It has also been associated with chronic prostatitis. Diagnosis is made microscopically by identification of the motile protozoan on a wet-mount slide prepara- tion. The pH of the discharge usually is greater than 6.0. Newer point-of-care tests include an antigen-based diag- nostic test (OSOM Trichomonas Rapid Test), a DNA probe test (Affirm VP III), and a PCR-based test. The OSOM and DNA probes have greater sensitivity than a vaginal mount and results can be available in less than