52 Sexually transmitted enteric infections
A wide variety of microbial pathogens may be transmitted sexually by the oral–anal or genital–anal routes. Sexually transmitted enteric infections may involve multiple sites of the gastrointestinal tract, resulting in proctitis, proctocolitis, and enteritis. These infections occur primarily in men who have sex with men (MSM) and heterosexual women who engage in anal–rectal intercourse or in sexual practices that allow for fecal–oral transmission. Anorectal infections with syphilis, gonorrhea, condyloma acuminata (human papillomavirus, HPV), lymphogranuloma venereum (LGV), and granuloma inguinale (donovanosis) have been recognized for many years. Over the past 2 decades, other sexually transmitted pathogens such as herpes simplex virus (HSV) and Chlamydia trachomatis have also been recognized as causing anorectal infection. Enteric pathogens traditionally associated with food or waterborne acquisition but that also may be transmitted sexually include Giardia lamblia, Entamoeba histolytica, Campylobacter, Shigella, and Salmonella. In patients with acquired immunodeficiency syndrome (AIDS), other opportunistic infections, including Candida, Microsporida, Cryptosporidium, Isospora, Cyclospora, Mycobacterium avium complex, and cytomegalovirus (CMV), may also cause intestinal disorders.
Depending on the pathogen and the location of the infection, symptoms and clinical manifestations vary widely. Perianal lesions are usually caused by syphilis, HSV, granuloma inguinale, chancroid, and condyloma acuminata. Rectal infections cause inflammation of the rectal mucosa, commonly referred to as proctitis. Symptoms include constipation, tenesmus, rectal discomfort or pain, hematochezia, and a mucopurulent rectal discharge. Proctitis can be caused by gonorrhea, chlamydia, syphilis, and HSV. Proctocolitis involves inflammation extending from the rectum to the colon, and in addition to the organisms causing proctitis, other enteric pathogens such as Shigella, Salmonella, Campylobacter, E. histolytica, and CMV may be involved. Enteritis is an inflammatory illness of the duodenum, jejunum, and/or ileum. Sigmoidoscopy results are often normal, and symptoms consist of diarrhea, abdominal pain, bloating, cramps, and nausea. Additional symptoms may include fever, weight loss, myalgias, flatulence, urgency, and, in severe cases, melena. Sexually transmitted pathogens usually associated with enteritis include Shigella, Salmonella, Campylobacter, Giardia, CMV, and, potentially, Cryptosporidium, Isospora, and Microsporida.
The large number of infectious agents that cause enteric and anorectal infections necessitate a systematic approach to the management of these conditions. While obtaining the medical history, the clinician should attempt to differentiate between proctitis, proctocolitis, and enteritis and should assess the constellation of symptoms that suggest one or another likely infectious cause. The history should be used to investigate types of sexual practices and possible exposure to the pathogens known to cause intestinal infections. Examination should include inspection of the anus, digital rectal examination, and anoscopy to identify general mucosal abnormalities. Initial laboratory tests should include a Gram stain of any rectal exudate obtained with the use of an anoscope. The demonstration of leukocytes provides objective evidence of the presence of an infectious or inflammatory disorder. Cultures for gonorrhea should be obtained from the rectum, urethra, and pharynx, and, if possible, rectal culture for chlamydia should be performed. Serologic tests for syphilis should be performed in all cases. Dark-field examination of any ulcerations and a rapid plasma reagin test should be performed. Cultures for HSV should be performed if ulcerative lesions are present. If proctocolitis is present, additional stool cultures for Campylobacter, Salmonella, and Shigella should be obtained, and stool examination for E. histolytica is indicated. For human immunodeficiency virus (HIV)-positive patients, other pathogens, including Microsporida, CMV, atypical Mycobacteria, Cryptosporidium, and Isospora, should be screened for by stool examination and cultured. Specific information on clinical presentation, diagnosis, and therapy is provided in other chapters on gastroenteritis, intestinal protozoa, and individual enteric pathogens.
Rectal infection with Neisseria gonorrhoeae occurs predominantly among homosexual men and women engaging in anal–rectal intercourse. In many cases of women, the patient has no history of rectal intercourse and the infection is thought to have resulted from contiguous spread of infected secretions from the vagina. Symptoms, when present, develop approximately 5 to 7 days after exposure. Symptoms are usually mild and include constipation, anorectal discomfort, tenesmus, and a mucopurulent rectal discharge that may cause secondary skin irritation, resulting in rectal itching and perirectal erythema. Although asymptomatic or mild local disease is common, complications such as fistulas, abscesses, strictures, and disseminated gonococcal infection may occur.
Findings of rectal gonorrhea during anoscopy are nonspecific and limited to the distal rectum. The most common finding is the presence of mucopus in the rectum. The rectal mucosa may appear completely normal or demonstrate generalized erythema with local areas of easily induced bleeding, primarily near the anal–rectal junction. Diagnosis is usually made by Gram stain and culture of material obtained by swabbing the mucosa of the rectal area. The sensitivity of Gram stain of rectal exudate for identification of gram-negative intracellular diplococci is approximately 80% when obtained through an anoscope versus 53% for blindly inserted swabs. Cultures inoculated on selective media provide the definitive diagnosis; however, the precise sensitivity of a single rectal culture for gonorrhea may be no greater than 80%. DNA detection assays are now widely available for detection of gonorrhea in urogenital specimens and appear to be equally sensitive as culture.
Due to increasing antibiotic resistance of gonorrhea to cefixime and fluoroquinolones, the Centers for Disease Control and Prevention (CDC) recommends for treatment of uncomplicated urogenital, anorectal, and pharyngeal gonorrhea, combination therapy with a single intramuscular dose of ceftriaxone 250 mg plus either a single dose of azithromycin 1 g orally or doxycycline 100 mg orally twice daily for 7 days. Clinicians who diagnose gonorrhea in a patient with persistent infection after treatment (treatment failure) with the recommended combination therapy regimen should culture relevant clinical specimens and perform antimicrobial susceptibility testing of N. gonorrhoeae isolates. When ceftriaxone cannot be used for treatment of urogenital or rectal gonorrhea, two alternative options are available: cefixime 400 mg orally plus either azithromycin 1 g orally or doxycycline 100 mg twice daily orally for 7 days, or azithromycin 2 g orally in a single dose if ceftriaxone cannot be given because of severe allergy. If a patient with gonorrhea is treated with an alternative regimen, the patient should return 1 week after treatment for a test-of-cure at the infected anatomic site. For all patients with gonorrhea, every effort should be made to ensure that the patients’ sex partners from the preceding 60 days are evaluated and treated for N. gonorrhoeae with a recommended regimen. If there is continued evidence of proctitis, further evaluation for other agents such as chlamydia, syphilis, enteric bacterial pathogens, and HSV should be considered.
Rectal infection with LGV and non-LGV immunotypes of C. trachomatis