The characteristic motility of cholera vibrios, as viewed through a dark-field microscope, and the adhesiveness of chicken cell-positive vibrios provide a means for rapidly identifying and biotyping cholera vibrios. Dilute suspensions of vibrios, such as one might find in a fresh rectal swab specimen from a cholera patient, when mixed with a 0.25% suspension of chicken erythrocytes in saline, can be used to biotype the cholera vibrios without prior isolation in pure culture. This is accomplished by using a dark-field microscope through which the chicken cell-positive cholera vibrios are observed to attach to the scattered erythrocytes and to propel them with a characteristic flipping motion.
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