Pseudomonadaceae representatives Pseudomonas anguilliseptica Evidence suggests

Pseudomonadaceae representatives pseudomonas

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Pseudomonadaceae representatives Pseudomonas anguilliseptica Evidence suggests that isolates are homogenous (Lopez-Romalde et ai, 2003). Pseudonwnas anguillisep tic a A homogeneous group of Gram-negative, asporogenous rods, which are motile by means of single polar flagella. Electron microscopy of 18-hour-old cultures on TSA reveal the presence of long, slightly curved rods with rounded ends. The size of these cells has been estimated as 5-10 x 0.8 mm. In addition, many bizarre forms have been observed. Fluorescent pigment is not produced. There is no reaction in the oxidative-fermentative test. Catalase and oxidase are produced, but not arginine dihydrolase, P-galactosidase, H2S or indole. Nitrates are not reduced. Gelatin, Tween 20 (variable result) and Tween 80 are degraded, but not blood, DNA, starch (variable result) or urea. Acid is not produced from arabinose, fructose, galactose, glucose, glycerol, inositol, lactose, maltose, man- nitol, mannose, raffinose, rhamnose, salicin, sucrose or xylose. Citrate is utiHsed by some isolates. Growth occurs at 5-30°C but not 37°C, in 0-4% (w/v) sodium chloride, and at pH 5.3-9.7. The G + C ratio of the DNA is 56.5-57.4 mol % (Wakabayashi and Egusa, 1972; Muroga et ciL, 1977b; Nakai and Muroga, 1982; Stewart et ciL, 1983; Lopez-Romalde et al, 2003).
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Characteristics of the pathogens: Gram-negative bacteria 133 On the basis of phenotypic traits, evidence suggests that isolates are homogenous (Lopez-Romalde et ai, 2003). However, other approaches have detected some varia- tion. Thus, a comprehensive examination of 96 isolates indicated the presence of two antigenic groups. Type I was not agglutinated in unheated antisera (this was prepared against heat-killed cells), although clumping (agglutination) of the cells subsequently occurred after the antiserum was heated to 100°C for 2h (or 121°C for 30min). Type II lacked this inhibition. It was speculated that this thermolabile agglutination- inhibiting antigen corresponds to the so-called K-antigens of coHforms (Nakai et al, 1981, 1982a, b). Molecular traits based on PFGE have revealed four types among 54 isolates from sea bream in Portugal and Spain (Blanco et al, 2002). Results with RAPD revealed two groups related to the host of origin of the cultures, with most of the isolates from eels in one cluster and the second grouping comprising isolates from other fish species (Lopez-Romalde et ai, 2003). From the phenotypic traits, Wakabayashi and Egusa (1972) concluded that the causal agent of Sekiten-byo corresponded to a new centre of variation within "Group III" or "Group IV" of the genus Pseudomonas. This opinion was reached because the pathogen was Gram-negative, rod-shaped, motile by polarly located flagella, insen- sitive to the vibriostatic agent (0/129), and produced catalase and oxidase, but not acid from glucose or, for that matter, diffusible (fluorescent) pigment. Because the strains were dissimilar to other fish-pathogenic pseudomonads, namely Ps. fluores- cens, a new taxon was proposed, i.e. Ps. anguilliseptica. We are sceptical about the validity of this proposal because the description could equally fit Alcaligenes or Deleya as well as
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  • Bacteria, representative, gram-negative bacteria

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