This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
Chlamydia are isolated by : 
Select and explain. 
A. Enzyme immune assay, B. Yolk sac inoculation, C. Direct immunofluorescence, D. Micro immunofluorescence
B: Yolk sac inoculation
Answer: B: Yolk sac inoculation 
Explanation: Isolation of chlamydiae can done by :
Inoculationinto yolk sac/embryonated eggs of 6-8 day old chick embryo which may be pretreated by streptomycin or polymyxin
Inculation into experimental animals (mice)
Tissue/cell culture :
Preferred mode
Commonly used cell lines are McCoy and HeLa cells.
Cell cultures are pretreated by irradiation or chemicals such as 5-iodo – 2 deoxyuridic or cycloheximide to enhance replication and detection of inclusion bodies.
Pretreatment with DEAE dextrax or centrifugation after inoculation, promotes contact between chlamydiae particles and cell monolayer.