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: Microbiology
Dark ground microscopy is used for - 
Select and explain. 
A. TPI, B. FTA - ABS, C. Kahn's test, D. VDRL
A: TPI
Answer: A: TPI 
Explanation: In TPI test, the serum of patient is incubated with complement and T. pallidum maintained in a complex medium anaerobically. If the antibodies are present, the treponemes are immobilized, that is, rendered nonmotile, when examined under dark ground illumination.