**4. Rectal** *C. trachomatis* **infection**

*C. trachomatis* is the most common bacterial sexually transmitted infection in the world. There were an estimated 4 million cases of chlamydia in the United States in 2018 [41]. This has made it the most frequently reported condition nationally. Despite public health chlamydia control programs, its frequency has increased over the past 20 years [42]. Chlamydial infections are more common in young women (<25 years), especially Black, Hispanic, and Native American women, and homosexual men [43]. *C. trachomatis* infects epithelial cells of the oropharynx, genitourinary tract, and gastrointestinal tract. The rectum is increasingly recognized as a common anatomical site of *C. trachomatis* infection in humans. *C. trachomatis* is a common cause of symptomatic proctitis and proctocolitis, especially in homosexual men [8]. While 10–15% of homosexual men who apply to sexual health clinics have a positive rectal chlamydia test, this rate is 8–9% in cisgender women. Despite the high prevalence of rectal chlamydial infections, there is a lack of knowledge about the biological, epidemiological, and clinical aspects of these infections. Asymptomatic rectal carriage of *C. trachomatis* can occur in infants and adults. 85% of rectal *C. trachomatis* infections are asymptomatic. However, rectal infection is known to cause proctitis. Infection with the L1, L2, and L3 serotypes of *C. trachomatis* can cause lymphogranuloma venorum syndrome. The most common clinical manifestation of rectal LGV is proctocolitis, while urogenital LGV is inguinal and femoral painful and tender lymphadenopathies [44]. Despite the prevalence of L serotype *C. trachomatis* among homosexual men, 25–50% of these infections are asymptomatic [45]. Although there is a high prevalence of chlamydia among women in sexual health clinics, this has no clinical significance. It is not clear whether rectal *C. trachomatis* is auto-inoculated from the rectum to the genital tract, and if so, how often. Such auto-inoculation has been demonstrated in animal models [32, 46]. However, this auto-inoculation has not been proven in humans. Along with that, in several epidemiological studies, it has been emphasized that undiagnosed or inadequately treated rectal *C. trachomatis* infection may be the source of recurrent urogenital chlamydia infection in women [47, 48]. Rectal *C. trachomatis* has been described in many ways. The primary means of acquiring rectal *C. trachomatis* among homosexual men are through receptive anal sex. Apart from this, there are several articles showing that oral-anal sex, use of sex toys, fingering, and use of saliva as a lubricant may lead to rectal *C. trachomatis* acquisition [49, 50].

Considering that the prevalence of rectal chlamydia in women is similar between those who report and do not report anal sex, it is unlikely that anal sex is the primary route of acquiring of rectal *C. trachomatis* in women [51]. Considering the anatomical proximity of the vagina and anus, toilet hygiene practices, and the positive rectal *C. trachomatis* test in most (70%) women with urogenital *C. trachomatis*, many women can get rectal chlamydia from urogenital *C. trachomatis* infection. There are articles showing that up to 87% of rectal *C. trachomatis* infections in women are acquired from urogenital infections [52]. Several researchers have suggested that oral ingestion of *C. trachomatis* infection (through penile-oral sex) may lead to rectal chlamydia. In this case, in order for *C. trachomatis* to colonize and infect the large intestine, it must survive passing through the upper gastrointestinal tract. This has been demonstrated in animal models [30, 53, 54]. In humans, this has not been demonstrated experimentally, although is supported by some epidemiological evidence [55, 56]. We have stated that asymptomatic rectal carriage of *C. trachomatis* can be seen in infants and adults. However, we also emphasize that *C. trachomatis* is a common cause of symptomatic proctitis and proctocolitis [8]. Both LGV serotypes and D to K serotypes can cause these clinical presentations. The severity and prevalence of the infection also vary accordingly. Infection with agents other than LGV serotypes usually occurs by direct inoculation of the agent during anal intercourse. It remains as a limited superficial inflammation in the rectum. Its main symptoms include anal itching and mucus rectal discharge. LGV serotypes, on the other hand, come to the infection site by lymphatic spread and cause ulcers, granulomas, and cryptic abscesses in the rectum and colon mucosa. They cause symptoms such as rectal pain, tenesmus, rectal bleeding, and fever. Perirectal abscesses, rectovesical fistulas, strictures due to fibrous tissue formation in the intestinal wall, and lymphoid tissue accumulation similar to hemorrhoids due to obstruction of lymphatic drainage may occur in untreated individuals, and the infection may be confused with inflammatory bowel diseases [8]. Methods used in diagnosis include cytological examination, isolation in cell culture, antigen determination, serological examinations, and molecular methods in which nucleic acid of the agent is detected [8, 57, 58]. NAATs are one of the most sensitive tests used in the examination of samples [59, 60] and are recommended for use in diagnosing chlamydia infection [38]. *C. trachomatis* culture has been generally abandoned. Since there is no significant difference in the outcome between the samples taken by the clinician and the samples taken by the patient themself, the patient's sampling themself can be used for rectal chlamydia infection detection [61, 62]. In chlamydia screening by NAAT, especially in cases where it is difficult to reach the clinician, the patient's own samples can be an alternative to the samples taken by the clinician.

#### **4.1 Treatment**

Treating people infected with *C. trachomatis* and their partners is of great importance in preventing reproductive health-related complications, stopping the transmission of the disease to individuals, and preventing re-infection. Doxycycline and azithromycin are the most commonly used drugs for the treatment of rectal chlamydia. Before 2020, the treatment guidelines for sexually transmitted infections recommended azithromycin 1 g orally as a single dose or doxycycline 100 mg orally 2x1 for 7 days for the treatment of rectal chlamydia infection. As alternative treatments, erythromycin base 500 mg orally 4x1 for 7 days or erythromycin 800 mg orally for 4x1 7 days or levofloxacin 500 mg orally 1x1 for 7 days or ofloxacin 300 mg 2x1 for 7 days can be used. Many clinicians prefer to use azithromycin because of the ease of use of

#### *Chlamydia and the Gastrointestinal System DOI: http://dx.doi.org/10.5772/intechopen.110485*

single-dose therapy and the possibility of treatment under direct supervision. In the gonorrhea treatment guideline, which was renewed in 2020, it is recommended to use doxycycline for treatment in cases where rectal chlamydial infection is not excluded. In the sexually transmitted diseases guide published in 2021, doxycycline was presented as a revised recommendation as the treatment of choice for chlamydia treatment [44, 63]. Recommendations for the treatment of rectal chlamydia have long been derived from studies of urogenital chlamydia. However, in some observational studies, it has been shown that azithromycin is less effective than doxycycline, and the difference in effectiveness in the rectum is greater than in the urogenital region [64, 65]. Two randomized controlled trials have recently been published on the treatment of rectal chlamydia among homosexual men. These studies compared azithromycin with doxycycline. While microbiological cure was achieved at a rate of 74–76% in the azithromycin group, this rate was found to be 97–100% in the doxycycline group [48, 66]. Results showing that doxycycline is superior to azithromycin in the treatment of rectal chlamydia in cisgender women have been suggested [67]. In light of this information, doxycycline treatment may be the first choice in the treatment of rectal chlamydia. In patient groups where treatment compliance may be low, direct single dose azithromycin may be preferred for treatment. If possible, it can be ensured that the patient is taking the drug under the supervision of the physician. Again, in cases where 7-day treatment with doxycycline will be given, the first dose can be given immediately and under the supervision of a physician. In order to minimize the transmission of the disease to sexual partners, it should be recommended that the patient abstain from sexual activity for the next 7 days if they received a single dose of treatment, and if they received 7 days of treatment, to abstain during the treatment and until the symptoms completely regress. To minimize the risk of re-infection, it is important for people with multiple sexual partners to avoid intercourse until all partners have completed their treatment.

#### **4.2 Sexual partner management during treatment**

All partners who have had sexual intercourse with the patient up to 60 days before the onset of symptoms of the disease should be tested for chlamydia infection. Although the frequency of intercourse and the time elapsed since the last intercourse affect the risk of transmission of the disease, the last sexual intercourse partner (even if more than 60 days have passed since the last sexual intercourse) must be treated. In cases where the partners cannot reach the doctor and medical services directly, sending the prescription or the drugs themselves to the patient's partner can also be considered as an option. It has been shown that such practices significantly reduce the risk of persistent or recurrent infections [68–70]. In homosexual individuals, since chlamydial infection is likely to be accompanied by other sexually transmitted diseases (especially undiagnosed HIV infection), partners should be thoroughly evaluated by a physician before being treated. Suggesting that patients come with their partners during followup visits may also make partner treatment more effective. To prevent re-infection, patients' partners should be advised to abstain from sexual intercourse until the disease is completely cured (within 7 days after a single dose treatment or until the end of treatment in 7 days of treatment) and until the symptoms have completely receded.

#### **4.3 Post-treatment follow-up**

Re-testing 3–4 weeks after the end of treatment is not recommended except in cases where there is doubt about the patient's compliance with treatment, when

symptoms persist, or when re-infection is suspected. Performing the NAAT test earlier than 3 weeks after the end of the treatment may lead to false positive results since non-viable microorganisms can still be found in the body. Therefore, in cases where recovery is uncertain and retesting is required, at least 3 weeks should have passed since the first treatment before the test [38, 71].
