Dark ground microscopy is used for diagnosis of

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.