Characteristics of the pathogens Gram positive bacteria 57 reaction Nitrates

Characteristics of the pathogens gram positive

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Characteristics of the pathogens: Gram-positive bacteria 57 reaction. Nitrates were reduced. DNA and gelatin were attacked. Citrate was utilised. Although there are insufficient data for a meaningful comparison with other taxa, it is interesting to note that streptococci are normally associated with the production of white colonies. Vagococcus salmoninarum In 1968, a so-called lactobacillus was recovered from diseased adult rainbow trout in Oregon and later subjected to detailed taxonomic examination. This isolate, desig- nated OS1-68T, has become the type strain of Vagococcus salmoninarum (Wallbanks et al, 1990). Further isolates have been studied by Schmidtke and Carson (1994). Vagococcus salnwninaruna Cultures comprise short or oval non-motile, facultatively anaerobic. Gram-pos- itive rods, which produce H2S but not arginine dihydrolase or catalase. Aesculin and blood (ot-haemolysis), but not sodium hippurate or urea, are degraded. Nitrates are not reduced. The Voges Proskauer reaction is negative. Acid is produced from amygdalin, arbutin, N-acetylglucosamine, cellobiose, fructose, P-gentiobiose, glucose (gas is not produced), maltose, mannose, ot-methyl-D-glu- coside, ribose, salicin, starch, sucrose, D-tagatose and trehalose, but not from D- or L-arabinose, D- or L-arabitol, adonitol, dulcitol, erythritol, D- or L-fucose, galactose, gluconate, glycogen, glycerol, 2 or 5-keto-gluconate, inuHn, inositol, lactose, D-lyxose, melibiose, melezitose, methyl-xyloside, methyl-D-mannoside, mannitol, rhamnose, raffinose, sorbose, sorbitol, D-turanose, D- or L-xylose or xylitol. Growth occurs at 5 to 30°C but not 40°C, and at pH 9.6. The major cellular fatty acids are of the straight-chain saturated and mono-unsaturated types. The G + C ratio of the DNA has been calculated as 36.0-36.5 mol %. Based on an examination of only one culture of Vag. salmoninarum, it was estabhshed that 96.3% homology with Vag.fluvialis was recorded in the 1,340-nucleotide region of the 16S rRNA. Slightly lower homology values of 94.5%, 94.1%, 94.0%, 93.8% and 93.7% were obtained with En. durans, Car. divergens, En. avium, Car. piscicola and Car. mobile, respectively. Despite the very high similarity to Vag.fluvialis, strain 051-68T was described in a new species, as Vagococcus salmoninarum. It remains for the examination of further isolates to determine the level of genetic variability within the taxon.
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58 Bacterial Fish Pathogens Streptococcaceae representatives Lactococcus garvieae (= Enterococcus seriolicida) The first attempt at clarifying the taxonomic status of the causal agents of strepto- coccicosis/streptococcosis was the landmark publication of Kusuda et al. (1991), who described a new species, i.e. Enterococcus seriolicida, to accommodate 12 isolates recovered from eels and yellowtail in Japan. Lactococcus garvieae Cultures were described as comprising non-motile, facultatively anaerobic. Gram- positive cocci in short chains, which do not produce catalase, H2S, indole or oxidase. Blood is degraded (oc-haemolysis). Aesculin and arginine are hydrolysed, but not so casein, gelatin or sodium hippurate. Acid is produced from a wide range
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