This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Spirochetes, Subject name: Microbiology
Dark ground microscopy is used for diagnosis of 
Select and explain. 
A. Spirochaete, B. Myco-tuberculosis, C. Myco-leprae, D. Mycoplasma
A: Spirochaete
Answer: A: Spirochaete 
Explanation: Ans. a (Spirochete). (Ref. Harrison, Principles of Medicine, 18th/Chapter 169. Syphilis)# Dark ground microscopic examination is useful but negative results does not exclude diagnosis of syphilis.# Diagnosis by microscopy is applicable in primary and secondary stages and congenital syphilis.# Wet film prepared with exudates is seen under dark ground microscope.# T.pallidum show slow movement with slender spiral structure.# However, serology remains the best diagnostic test for syphilis.Educational point:# In blood transfusion and in congenital syphilis, no chancre occurs.