Chlamydia is a type of prokaryotes that is smaller than bacteria and can pass through bacterial filters. They have a spherical or elliptical shape whose sizes range from 0.2μm to 1.5μm. Like other prokaryotes, they have ribosomes and a nucleoid region with circular DNA in their cytoplasm. Although they are Gram-negative, the cell walls lack peptidoglycan which is common in other gram-negative bacteria, making them resistant to antibiotics that target this component.
They lack a complete enzyme system and are unable to synthesize ATP. This means that Chlamydia survives within the host cells of living organisms. In the laboratory, Chlamydia cannot be cultured using agar or gelatin-based media, but it can be grown using live cells, such as chicken embryos.
Chlamydia have a unique life cycle that involves alternating between two different forms. The elementary bodies, with a thick cell wall, are small spherical granules with a diameter of 0.2-0.4μm. They are metabolically inactive and can resist environmental stress. They enter the human body through respiratory droplets or contact, and are taken up by cells through phagocytosis. Within the host cell, the elementary bodies transform into metabolically active, non-infectious reticulate bodies. They appear as large spherical granules with a diameter of 0.6-1.5μm and have a thin cell wall. The reticulate bodies utilize the host's energy and nutrients to synthesize their own proteins and genetic material. They undergo binary fission to generate inclusions that contain a large number of reticulate bodies. When the number of chlamydia in the inclusions reaches a certain threshold, some reticulate bodies begin to differentiate back into elementary bodies. The mature elementary bodies are released from the host cells, usually through lysis of infected cells or extrusion of inclusions. These released elementary bodies can then infect neighboring cells or be transmitted to new hosts, initiating a new infection cycle (lasting 48-72 hours).
Chlamydia are responsible for various diseases in humans and animals.
The surface lipopolysaccharides and proteins of Chlamydia can produce endotoxins similar to those found in gram-negative bacteria. Chlamydia can avoid phagocytosis of lysosomes to proliferate, and depleted resources lead to cell death.
Transmission
①Chlamydia is primarily transmitted through sexual contact, including vaginal, anal, or oral sex. Factors such as multiple sexual partners and lack of condom use increase the risk of infection.
②Respiratory droplets can also spread Chlamydia, such as when an infected individual coughs or sneezes.
③Indirect contact is another route of Chlamydia transmission. Sharing towels, clothing, or medical instruments with an infected individual, or even being in the swimming pool, can lead to infection.
④Infants born to mothers with Chlamydia may be infected, and up to half of these infants will have this disease at birth.
Symptoms
Chlamydia often causes diseases of the genitourinary system, characterized by painful urination, urge to urinate more often, and increased abnormal discharge from the urethra. However, this infection has a long incubation period, and the lack of symptoms can result in undiagnosed cases. Many cases are only detected several months or years after infection. If left untreated, it can lead to pelvic inflammatory disease in females and orchitis in males, ultimately resulting in reproductive damage and infertility.
Chlamydia can invade the eyes to cause conjunctivitis characterized by redness, pain, and mucous discharge. In certain areas with poor sanitation and limited healthcare services, this long-term chronic infection can lead to scarring of the eyelids and cornea, ultimately blindness.
Chlamydia pneumoniae can cause respiratory tract infections in humans, including pneumonia, bronchitis, and pharyngitis. These respiratory infections typically manifest as symptoms such as cough, chest discomfort, and difficulty breathing.
Prevention and Treatment
Oral antibiotics such as tetracycline and macrolides can effectively clear Chlamydia within 1-2 weeks. It is recommended to undergo follow-up testing to confirm the eradication of the infection. Sexual partners should be treated simultaneously.
To prevent reinfection and the spread of chlamydia, it is important to practice safe sex by using condoms consistently and correctly. Regular screening, particularly for sexually active individuals, especially those with multiple partners, is also crucial for early detection and prompt treatment of chlamydia infections. Avoid using other people's belongings, especially shared towels in hotels. Refrain from touching the eyes before washing hands.