Deoxyribonucleic Acid Reassociation Experiments with a Halophilic, Lactose-Fermenting Vibrio Isolated from Blood Cultures

Abstract

Hollis et al. (J. Clin. Microbiol. 3:425-431, 1976) recently described an apparently new group of bacteria, with characteristics of the genus Vibrio, which was isolated from human blood, spinal fluid, and local infections of the extremities, and which caused fatal fulminant septicemia in at least 5 of 38 cases. The organisms were morphologically and biochemically similar to, but not identical with, both Vibrio alginolyticus and V. parahaemolyticus; they had different isolation sources from those of the latter two species, and they also fermented lactose and possessed different tolerances for sodium chloride in nutrient broth. This paper reports the results of deoxyribonucleic acid (DNA) reasociation experiments, which showed that DNA fragments from six strains of the newly described organisms, incubated at 60°C with DNA fragments from V. alginolyticus, V. cholerae, and V. parahaemolyticus, resulted in DNA duplex formation showing a level of relatedness consistent with that of different species within a genus. All strains of the newly described vibrio were highly related. Incubation at 75°C produced less than 10% relative duplex formation. When tested for heat stability, these duplexes had low temperatures of dissociation, indicating imperfectly matched DNA molecules. We thus concluded that the newly described vibrio is a species distinct from the other species studied.