Changes in culture and biochemical characteristics of Salmonella paratyphi B after incubation in seawater]

After incubation in seawater Salmonella paratyphi B cells rapidly became unable to grow on bacteriological media. Previous adaptation to high osmolarity conditions greatly slowed down this process. Strains isolated from seawater microcosms after varying incubation periods were qualitatively different and showed changes in some of their growth (colony shape and size) and biochemical properties (acidification of some sugars, gelatinase activity, acetoin production, nitrate reduction). Because of these modifications, the bacteria showed atypical profiles and could not be identified as members of the Salmonella genus. The alteration of the phenotype, although reversible, could explain some of the false-negative results obtained upon isolation and identification of these bacteria in seawater samples.