TABLE 3.

Characteristics of V. cholerae O1 reference strains used in this study

Strain	Relevant characteristic	Reference
SM44	Derivative of El Tor strain P27459 in which the CTX genetic element was marked with a kanamycin resistance determinant by marker exchange disrupting the ctxAB operon	12
RV508	Derivative of classical biotype strain 569B which is known to constitutively express CT, TCP, and other toxR-regulated gene products	24
CVD103	Derivative of classical biotype strain 569B in which the ctxA gene was deleted to produce a vaccine prototype	15