TABLE 3.

Production of CT by environmental V. mimicus strains with integrated form of pMSF9.2, a genetically marked derivative of the RF of the CTXΦ genome carrying a functional ctxAB operon and encoding resistance to kanamycin

Strain	Characteristics	CT productiona (GM1 ELISA)	Fluid accumulationb in rabbit ileal loops (ml/cm of ileal loop)
569B	Toxigenic classical biotype strain of V. cholerae O1	6.13 ± 1.02	3.61 ± 0.51
P-27457	Toxigenic El Tor biotype strain of V. cholerae O1	2.87 ± 0.73	2.39 ± 0.47
2V-8	Wild-type CTX-negative V. mimicus strain	UD (<0.01)c	0
2V-8(MSF9.2)	Strain 2V-8 carrying integrated pMSF9.2	2.36 ± 0.42	2.16 ± 0.61
2V-8(CTX-Km)	Strain 2V-8 lysogenized with CTX-KmΦ	UD (<0.01)	0
88V-114	Wild-type CTX-negative, V. mimicus strain	UD (<0.01)	0
88V-114(MSF9.2)	Strain 88V-114 carrying integrated pMSF9.2	2.95 ± 0.72	2.45 ± 0.65
88V-114(CTX-Km)	Strain 88V-114 lysogenized with CTX-KmΦ	UD (<0.01)	0

^aToxin amounts are expressed in micrograms per unit of optical density of the culture at 600 nm. The values represent the averages of five independent observations in LB medium for the classical biotype strain and in AKI medium for the El Tor and V. mimicus strains. No significant difference in toxin production was noted when the El Tor and V. mimicus strains were tested in LB or AKI medium. 

^bValues represent averages of five independent observations made in different rabbits. 

^cUD, undetectable. The toxin amounts were less than 0.01 μg/ml, which was the lowest concentration of purified toxin used as a control (see the text for details).