Direct demonstration of V.cholerae is not recommended for general purposes. However, darting motility and its inhibition of specific antisera, especially after brief inoculation in broth, has proven valuable in experienced hands for presumptive diagnosis. The method is as follows:
Prepare a hanging drop from alkaline peptone water which has been inoculated with faeces and incubated at 37oC for 4-6 hours.
Examine it under high power dry lens of microscope.
Darting motility characteristic of vibrios is suggestive of diagnosis.