Intestinal fluid accumulation induced by oral challenge with Vibrio cholerae or cholera toxin in infant mice

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Abstract
The diarrheal response of orally inoculated infant mice to viable Vibrio cholerae and purified cholera toxin was quantitated by means of a fluid accumulation (FA) ratio. The FA ratio is defined as the gut weight/remaining body weight. FA ratios were determined in relation to time of exposure and dose. Onset of fluid accumulation with viable cells of strains CA401 and 569B occurred 8 h postinoculation and reached a near maximum of 16 h. A dose of 4 x 10(6) colony-forming units of strain CA401 was required for a positive response 16 to 18 h postinoculation. Several other classical cholera strains demonstrated a similar dose-related response. Strain 569B, however, required a 100-fold higher dose to give a positive response. Several mutant cholera strains were decreased virulence in other model systems elicited FA ratios decreased from wild-type values. Onset of fluid accumulation which cholera toxin occurred 6 to 8 h postinoculation and reached a maximum by 10 h. A dose of 0.5 microng was required for a positive response 10 to 12 h postinoculation. The positive response to toxin could be inhibited by preincubation with specific antitoxin.