In vivo evaluation of pathogenicity of clinical and environmental isolates of Vibrio cholerae

Thirty-three minimally passaged clinical and environmental isolates of Vibrio cholerae were examined for ability to survive and multiply in the upper bowel of infant mice and to elicit diarrhea. All of 21 smooth O-1 V. cholerae isolates from stool were able to multiply and elicit diarrhea. Three rough strains isolated from stool were unable to multiply or to elicit diarrhea. Two smooth O-1 isolates associated with cholera cases (from a sewer and a septic tank) also were able to cause disease. However, four O-1 strains and one non-O-1 strain from sources not associated with cholera cases did not cause mouse disease. A human gall bladder isolate was also avirulent, whereas a Louisiana shrimp isolated showed low mouse virulence. We conclude that smooth human diarrheal isolates of V. cholerae of serogroup O-1 are virulent for infant mice. Examination of sequential isolates from single patients showed that some strains isolated later in infection had a reduced ability to induce diarrhea. Comparison of epidemiologically related strains showed that an isolate from crab had a low ability to induce disease in infant mice, whereas the isolates from patients showed the expected ability to multiply and elicit diarrhea in mice.