Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Eleven cases of cholera occurred in Louisiana in 1978 and except for an isolated case in Texas in 1973, this was the first cholera outbreak in the United States since 1911. The source of the infectious agent was traced to the consumption of crabs, a finding which had adverse effects on the crab industry in Louisiana. During 1979 and 1980 blue crabs were examined bacteriologically for the presence of Vibrio cholerae, the etiological agent of Asiatic cholera, and other pathogenic Vibrio species. Four hundred-eighteen V. cholerae isolates were recovered from crab feces and 144 V. cholerae were recovered from hemolymph samples. Twenty per cent of crab hemolymph samples and 45% of fecal samples tested were positive for V. cholerae. The presence of V. cholerae varied inversely with the presence of halophilic Vibrio species. The incidence of Vibrio species in crab hemolymph and fecal samples showed seasonal variation. The V. cholerae isolates were serologically tested by side agglutination and were found to be non-01s. V. cholerae isolates from crabs, sewers, and canals in Louisiana were assayed for the production of cholera toxin by the ganglioside-ELISA method. Five non-01 V. cholerae isolated from canals produced cholera toxin at levels detected in this assay. Two other pathogenic species, Vibrio vulnificus and Vibrio fluvialis were frequently isolated from crabs. V. fluvialis isolates were examined for the production of toxic products by the rabbit skin test assay. All isolates tested gave positive skin test results. A 40,000 molecular weight permeability factor was purified from culture supernatant fluids of V. fluvialis strain DJVP 6957 by ion exchange chromatography and gel filtration. The use of deoxycholate during gel filtration steps was necessary to dissociate protein aggregates in culture supernatant fluids.