**16.** *Chlamydia pneumoniae* **and respiratory infections**

**Clinic:** *Chlamydia pneumoniae* is known as the TWAR agent. A serotype has been identified. It is pathogenic in humans. It is transmitted by respiratory secretions. They are causative agents of upper and lower respiratory tract diseases, most of which are asymptomatic. They cause atypical pneumonia and inflammatory atherosclerosis and cardiovascular diseases [28]. The seropositivity rate is quite low under the age of five. The incidence begins to increase in school-age children. The incidence in adults and the elderly is around 50–75% [29]. The sex-related seropositivity rate in children is equal. However, it is significantly more common in males than adults. Today, studies are still ongoing to explain this difference [30].

**Laboratory diagnosis:** Many laboratory tests have been developed for the diagnosis of *Chlamydia pneumoniae*. However, serological tests are frequently used.

**Culture:** For *Chlamydia pneumoniae*, oropharyngeal swab samples should be transported with a chlamydia transport medium (sucrose phosphate glutamic acid buffer solution). Sputum samples are not suitable. It should be kept in a refrigerator at +4°C before being sent to the laboratory. They die quickly at room temperature. *C. pneumoniae* grows better in HL and Hep-2 cells. They are incubated for three days at 35°C. They are usually detected by fluorescent antibody staining with monoclonal antibodies specific for *C. pneumoniae* [11, 31].

**Serology:** Microimmunofluorescence (MIF), a serological test method, is the most sensitive method. It is species-specific. IgM increases 2–3 weeks after primary *The Laboratory Diagnosis of* Chlamydia *Infections DOI: http://dx.doi.org/10.5772/intechopen.110464*

infection and IgG increases 6–8 weeks later. In reinfections, there may be no increase in IgM and after 1–2 weeks there may be an increase in IgG [3].

**Nucleic acid amplification methods**: The PCR method is used to determine the agents in the pharyngeal swab, bronchoalveolar lavage, and sputum samples. This method is a sensitive and rapid diagnostic test [32].

**Treatment:** *Chlamydia pneumoniae* are sensitive to macrolides, fluoroquinolones, and tetracyclines. Treatment success is good in patients treated with doxycycline, azithromycin, or clarithromycin. However, after some routine treatments, symptoms of the disease continue or reinfections are observed. Therefore, drugs should be used for 10–14 days [11].
