**1. Introduction**

Chlamydias are small gram-negative, obligate intracellular living microorganisms, preferably infecting squamocolumnar epithelial cells. The microorganisms can be divided into two subtypes as Chlamydia (e.g., *C. trachomatis*) and Chlamydophila (e.g., *Chlamydophila pneumoniae* and *Chlamydophila psittaci*). *C. trachomatis* is divided into 19 different serological variants (A, B/Ba, C, D/Da, E, F, G/Ga, H, I/Ia, J, K, L1, L2, L2a, and L3) according to monoclonal antibody-based analyses and variants that are classified according to ompA genotyping. Of these, types A, B, Ba, and C are the causative agents of Trachoma, an endemic serious eye disease in Africa and Asia; D-C strains lead to genital tract infections. L1-L3 strains cause Lymphogranuloma venereum disease, which is especially seen in tropical countries and is characterized by genital ulcers [1].

Chlamydia can affect various organs, and the genitourinary system is one of the major sites of this infection. It can cause clinical conditions in nasopharynx, epididymis, urethra, cervix, uterus, and salpinx [2–4]. It is the most reported sexually transmitted bacterial infection and one of the major causes of female infertility. This infection also leads to conjunctivitis, pneumonia, afebrile pneumonia syndrome (in vaginally born babies from infected mothers), and trachoma, a leading cause of

acquired blindness in the world and perihepatitis condition also known as Fitz-Hugh-Curtis syndrome [5].

There are one million sexually transmitted disease transmissions every day in the world [6]. The annual number of *C. trachomatis* genital infections reached 4 million annually in 2018, up from about 2.86 million cases in 2008 [7]. Research shows similar incidences in Germany [8], France [9], the Netherlands [10], New Zealand [11], and Australia [12]. In a report by the World Health Organization (WHO) Initiative for Vaccine Research (IVR) it is estimated that there are more than 140 million cases of *C. trachomatis* infection worldwide [13]. Chlamydia carrier rates in the sexually active female population are around 20%. This ratio is 2–3 times higher than the N. gonorrhea incidence.
