Nitrates are reduced Growth occurs at 15 37C and in 03 30 wv but not 0 and 7 wv

Nitrates are reduced growth occurs at 15 37c and in

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DNA, lipids and starch, but not aesculin, are degraded. Nitrates are reduced. Growth occurs at 15-37°C, and in 0.3-3.0% (w/v), but not 0% and 7% (w/v), sodium chloride. Citrate, malonate and tartrate are utiHsed. The organisms pro- duce acid from amygdalin, arabinose, cellobiose, galactose, glycerol, maltose, mannitol, sorbitol, sucrose and trehalose, but not from adonitol, dulcitol, ery- thritol, inositol, lactose, melibiose, raffinose, rhamnose, salicin or xylose. Cultures comprise a single, dominant ribotype. The G + C ratio of the DNA is 45.6-46.3
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Characteristics of the pathogens: Gram-negative bacteria 139 mol % (Smith, 1961; Kiehn and Pacha, 1969; Evelyn, 1971b; Muroga et ciL, 1976a, b; Schiewe et ciL, 1981; Austin et ciL, 1995a; Farmer III et al., 2005). It has been observed that some so-called bona fide isolates of V. anguillarum possess fascinating micromorphologies, insofar as broth cultures appear to contain two types of cells. Apart from the typical, short, motile rods, we have observed very small, highly motile cells, some of which are capable of passing through 0.22 |im porosity filters. From transmission electron microscopy, we beheve that these cells comprise extremely small, spherical bodies, each attached to a single polar flagellum. The significance of these small cells is unclear, but they may represent a stage in a life cycle, a laboratory artefact, or some form of survival mechanism. The results of serology further complicated the understanding of V. anguillarum (Bolinches et ai, 1990). The estabhshment of serotypes has traversed species (or phenetic) boundaries. Initially, three serotypes were recognised for isolates from northwestern (U.S.A.), Europe, and the Pacific Northwest (U.S.A.) (Pacha and Kiehn, 1969). This was supported by the work of Japanese scientists (Aoki et ai, 1981; Muroga et ai, 1984b). With further study, the number of serotypes increased to six (Kitao et ai, 1983). Thus, in a mammoth study of 267 isolates from ayu, eel and rainbow trout, Kitao and co-workers defined serotypes A, B, C, D, E, and F as a result of cross-agglutination and cross-absorption tests with thermo-stable "O" (somatic) antigens. The majority (243) of these Japanese isolates were recovered in serotype A. It is noteworthy, however, that avirulent isolates were not recovered in any of these serotypes (Muroga et ai, 1984b). This reflects the nature of the LPS in the cell wall, which accounts for both the nature of the serotype (Johnson, 1977; Aoki et ai, 1981) and the immunogenicity. Later, Sorensen and Larsen (1986) reported the presence of 10 O-antigen serotypes, based upon examination of 495 isolates, repre- sentatives of which shared a common 40 kDa protein (Simon et ai, 1996). A common 47 kb plasmid was reported by Giles et al. (1995). Serovars (= serotypes/serogroups) Ol and 02 contained plasmids, but there was no apparent correlation between the presence of such extrachromosomal DNA and biochemical properties (Larsen and Olsen, 1991), although serogroup Ol was regarded as biochemically homogeneous (Pedersen and Larsen, 1995). The same 10 serogroups together with 6 non-typeable groups were described by Olsen and Larsen (1991). The number of serogroups was now increased to 16, i.e. Ol to 016 (Grisez and Ollevier, 1995).
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