tsükliine

Tsükliine, also known as cyclines, is a class of antibiotics derived from the bacterium *Streptomyces*. These compounds are widely used in both human and veterinary medicine due to their broad-spectrum antibacterial activity, particularly against Gram-positive bacteria and some Gram-negative organisms. The name "tsükliine" originates from the Estonian language, where "tsükliin" translates to "cycline," reflecting their cyclic chemical structure.

The first cycline antibiotic, tetracycline, was discovered in 1948 and remains one of the most commonly prescribed members of this class. Other notable examples include doxycycline, minocycline, and oxytetracycline, each varying slightly in their chemical structure and spectrum of activity. Cyclines work primarily by inhibiting bacterial protein synthesis by binding to the 30S subunit of the bacterial ribosome, preventing the attachment of aminoacyl-tRNA to the ribosome.

Tsükliine antibiotics are effective against a range of infections, including respiratory tract infections, urinary tract infections, acne, and certain sexually transmitted diseases. However, their use has declined in recent years due to the emergence of bacterial resistance, particularly resistance mediated by efflux pumps or ribosomal protection proteins. Overuse and misuse of cyclines have contributed to the spread of resistance, prompting efforts to limit their application where possible.

Common side effects of tsükliine antibiotics include gastrointestinal upset, such as nausea and diarrhea, as well as photosensitivity, where prolonged exposure to sunlight may cause skin reactions. They are generally contraindicated in children under eight years of age due to the risk of enamel hypoplasia in developing teeth. Additionally, cyclines should be avoided during pregnancy and breastfeeding, as they may pose risks to fetal development and infant health.

Tsükliine antibiotics are available in various formulations, including oral tablets, capsules, and intravenous injections, allowing for flexible dosing depending on the infection and patient needs. While they remain a valuable tool in antimicrobial therapy, their use is increasingly being guided by susceptibility testing to ensure optimal efficacy and reduce resistance development.