Unique properties of Chlamydia are Chlamydia is an obligate intracellular parasite. This means they can survive only by establishing residence inside Animal cells They need their host's ATP as an energy source for their own cellular activity. They are energy parasites using a Cell membrane transport system that uses ATP from the host system and gives out ADP. This obligate intracellular existence makes it impossible to culture these organisms on nonliving artibacterial media. Due to their small size and failure to grow in cell - free media they were considered to be viruses. Chlamydiae grows in cultures of a variety of eukaryotic cell lines Me Coy or HeLa cells. It may be necessary to Treat cells with poly anionic compounds such as DEAD-dextran to reduce the electrostatic barrier to infection. Antimetabolite such as cycloheximide is added to favour competition for host cell amino acid pools. All types of Chlamydiae proliferate in embryonated eggs particularly in the yolk sac. The special features in structure and chemical composition of chlamydiae are The outer cell wall resembles the cell wall of gram negative bacteria It has a relatively high lipid content It is rigid but it does not contain typical bacterial peptidoglycan; perhaps it contains a Tetrapeptide linked matrix. N Acetyl muramic acid also appears to be absent from chlamydiae cell wall Antibiotic susceptibility of chlamydiae. Penicillin binding proteins occur in chlamydiae cell wall and chlamydiae cell wall formation is inhibited by penicillins And other drugs that inhibit transpeptidation of bacterial peptidoglycan. But remember the important point about t/t, That cell wall inhibitors result in the production of morphologically defective forms but are not effective in clinical Disease. • Inhibitors of protein synthesis (tetracyclines, erythromycins) are effective in most clinical infections. Erythromycin Or tetracyclines are considered the drug of choice for chlamydiae infections.