**3. Treatment of** *Chlamydia trachomatis* **infection**

Males and females alike are most at risk for bacterial sexually transmitted infections (STIs) caused by *C. trachomatis*, a small gram-negative bacterium.

Preventing complicated infections caused by chlamydia and its sequelae are the primary goals of management (e.g., pelvic inflammatory disease, infertility, chronic pelvic pain, ectopic pregnancy, and epididymitis). The screening and treatment of young females for *C. trachomatis* infection, for example, has been shown to reduce the risk of subsequent PID [50]; however, early treatment of PID, particularly when *C. trachomatis* is detected, reduces the risk of ectopic pregnancy and infertility compared to delayed treatment [51]. Treatment with doxycycline or azithromycin results in clinical improvement in 83 and 86 per cent of symptomatic patients with cervicitis and urethritis, respectively [51, 52]. The risk of reinfection is high for persons who have previously contracted chlamydia. Persons with symptoms such as cervicitis, PID, urethritis, epididymitis, and acute proctitis may benefit from empiric therapy for chlamydial infection.

Empiric therapy should also be offered to patients recently exposed to chlamydia. A patient with documented gonococcal infection should also receive empiric chlamydia treatment unless the nucleic acid amplification test (NAAT) is negative [51].

#### **3.1 Antimicrobial susceptibility of C trachomatis**

Tetracyclines, macrolides, and some, but not all, fluoroquinolones are uniformly effective against *C. trachomatis* [53]. The in vitro persistence of *C. trachomatis* is associated with penicillins [53, 54], but amoxicillin has also been effective. The aminoglycosides and sulfonamides have limited activity against *C. trachomatis*, but antibiotic resistance is sporadic for those agents [55].

Moreover, the extracellular elementary body of *C. trachomatis*, an infectious organism, is metabolically inert and resistant to killing, so the breadth of active agents is limited [56]. Therefore, antibiotics need to target the sequestered intracellular and intravacuolar phases of this pathogen's life cycle, which is why antibiotics with good intracellular penetration are vital [57].

Maintaining antibiotic concentrations throughout the organism's life cycle, ranging from 36 to 48 hours, is also necessary. To ensure adequate levels of antibiotics, either a prolonged course of therapy or the selection of an antibiotic with a long half-life is required [57, 58].

Moreover, the elementary body is relatively inert, limiting replication opportunities and resulting in antibiotic-resistant mutations [59].

#### **3.2 Defining antibiotic efficacy**

As part of its four primary outcomes of recommending antimicrobial regimens for treating sexually transmitted infections (along with symptom resolution, prevention

Chlamydia trachomatis*: A Tiny Being beyond the Nature DOI: http://dx.doi.org/10.5772/intechopen.111425*

of sequelae, and prevention of transmission), the Center for Disease Control and Prevention explicitly incorporated microbial eradication (along with symptom resolution, prevention of sequelae, and prevention of transmission) to one of four outcomes. The effectiveness of a drug can be more reliably predicted by its ability to cure bacteria than by its ability to cure the patient for two reasons: many patients have other coinfections that are not responsive to treatment [59], and most patients are not manifesting clinical symptoms at the beginning of the treatment.

#### **3.3 Comprehensive treatment approach**

The complete care of C trachomatis-infected patients includes antibiotic treatment, evaluation, and treatment of other sexually transmitted diseases (STIs, such as gonorrhea and HIV), counseling on adherence and sexual activity, follow-up testing, and managing sex partners. Females and males are more likely to have asymptomatic infections that can only be detected on screening; however, these should also be treated promptly [56].

#### **3.4 Antibiotic treatment of chlamydia**

#### *3.4.1 Doxycycline as the preferred agent*

For optimal outcomes, patients should be counseled to adhere to the prescribed dosage of 100 mg twice daily for 7 days [60]. It is safe and effective to administer delayed-release doxycycline (200 mg daily for 7 days) compared with twice-daily doxycycline. However, it is more costly and may not be accessible to all patients [60]. Previously, azithromycin was considered an alternative option, but mounting evidence indicates that doxycycline is a more effective microbial agent, especially for rectal infections and possibly pharyngeal infections [61]. Azithromycin is now considered an alternative. For this reason, azithromycin is reserved for individuals who are unlikely to be able to complete the seven-day doxycycline course (e.g., patients with adherence issues) and is administered as a single, directly observed dose of 1 g. It is also the preferred antibiotic for pregnant women [62].

#### *3.4.2 Levofloxacin (500 mg orally once daily for 7 days)*

Levofloxacin and ofloxacin (300 mg twice daily for 7 days) are highly effective against *C. trachomatis*. There may be limited availability of this alternative fluoroquinolone. They are more expensive than doxycycline, and neither offers a significant advantage. Fluoroquinolones should not be used for uncomplicated infections since they are associated with severe adverse effects. Therefore, fluoroquinolones as a treatment for *C. trachomatis* is rare. Then, levofloxacin (or ofloxacin) can be used as an antichlamydial agent. Before, these fluoroquinolones were utilized primarily for treating coexisting gonococcal and chlamydial infections. Despite this, due to drug resistance, fluoroquinolones no longer provide adequate protection against *N. gonorrhoeae* [63, 64].

**Fluoroquinolones** are less well-studied for targeted therapy for *C. trachomatis* than doxycycline or azithromycin. Studies comparing fluoroquinolones (e.g., ofloxacin) to doxycycline have failed to demonstrate any difference in microbiologic cure rates. Fluoroquinolones are inappropriate; ciprofloxacin has poor microbiologic outcomes. Alternatively, moxifloxacin has not been studied as a targeted therapy for

*C. trachomatis*, it has shown promising efficacy in treating PID and is recommended as an alternative treatment regimen for select females with PID [65, 66].

**Penicillins and erythromycin** are significantly less effective than penicillin, resulting in a microbial cure, with cure rates ranging from 85 to 89%. Therefore, penicillins (such as amoxicillin) are primarily prescribed to pregnant women who cannot tolerate other antibiotics [67, 68].
