Enterobacteriaceae, fish

Several taxa of Enterobacteriaceae inclnding Morganella morganii, Proteus vulgaris, and Raoultella (Klebsiella) planticola are able to decarboxylate the amino acid histidine, which is abundant in the mnscle tissne of scombroid hsh (Yoshinaga and Frank 1982 Takahashi et al. 2003). The histamine produced has been associated with an incident of scombroid fish poisoning (Taylor et al. 1989). 

The enumeration of Enterobacteriaceae and Escherichia coli in water using SPC has been the subject of several studies. These microorganisms serve as indicators of faecal contamination as part of the monitoring of the quality of raw and partially purified waters. They are also used to demonstrate the compliance of a final product with legal standards. For the selective detection of viable Enterobacteriaceae, Baudart et al. (2002,2005) used a nucleic acid probe targetting the 16S rRNA. In order to enumerate the viable cells and to increase the fluorescence intensity, FISH was combined with a DVC procedure and TSA. Using this approach, as little as one fluorescent target cell could be demonstrated in the presence of lO -lO non-fluorescent other cells. 

All smoked fish must be stored chilled or vacuum-packed to prolong shelf life. Hansen and Huss [28] identified the microfiora on spoiled, sliced, and vacuum-packed cold-smoked salmon from three different sources. Lactic acid bacteria dominated the microfiora, in some cases large number of Enterobacteriaceae were also present. The microfiora on cold-smoked salmon appeared to be related to the source of contamination, i.e., the raw material and the smokehouse rather than specific for the product. 

Most marine fishes contain trimethylamine oxide (TMAO) this colorless, odorless, and flavorless compound is degraded to trimethylamine, which gives a fishy odor and causes consumer rejection. This compound is not present in land animals and freshwater species (except for Nile perch and tila-pia from Lake Victoria). TMAO reductase catalyzes the reaction and is found in several fish species (in the red muscle of scombroid fishes and in the white and red muscle of gadoids) and in certain microorganisms Enterobacteriaceae, She-tvanella putrefaciens). 

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