Thus in their publication it was concluded that the fish pathogens were most

Thus in their publication it was concluded that the

This preview shows page 77 - 80 out of 594 pages.

1984). Thus, in their publication it was concluded that the fish pathogens were most closely related to Lactobacillus yamanashiensis subsp. yamanashiensis in terms of G + C ratio of the DNA and fermentation profile. Subsequently, Collins et al. (1987) demonstrated closer relationships with other carnobacteria. GRAM-POSITIVE COCCI IN CHAINS General comments Since the first publication in 1958, there has been considerable confusion about the number of and the nature of the bacterial species involved in streptococcicosis/ streptococcosis. Thus, at various times the fish-pathogenic streptococci have been linked with Str. agalactiae, Str. dysgalactiae, Str. equi, Str. equisimilis, Str. (= En.) faecium, Str. pyogenes and Str. zooepidemicus. In addition, we have found that Enterococcus faecalis NCTC 775^, En. faecium NCTC 1\1\^, Lactococcus lactis NCFB 604, Str. mutans NCFB 2062 will cause similar diseases in Atlantic salmon and rainbow trout. Certain traits of the causal agent(s) have been repeatedly empha- sised as having supposedly taxonomic significance. In particular, the ability to attack blood has been highUghted. Thus, fish-pathogenic strains have been described, at one time or another, as either a- (Kusuda et al, 1976a; Al-Harbi, 1994) or P-haemolytic (Robinson and Meyer, 1966; Minami et al, 1979; Kitao et al, 1981; Ugajin, 1981; lida et al, 1986) or as non-haemolytic (Plumb et al, 1974; Cook and Lofton, 1975; lida et al., 1986). Superficially, this information could infer heterogeneity among the pathogens, although some well-established taxa, e.g. Str. agalactiae, contain both a- and P-haemolytic strains; Table 3.3). Nevertheless, many characteristics are shared by the majority of the fish pathogens. Yet, there is also some variance in the overall descriptions reported by different groups of workers (Table 3.3). For example, Boomker et al. (1979) reported that isolates, recovered from the Transvaal in South Africa, grew on MacConkey agar and at 45°C, hydrolysed sodium hippurate, and produced acid from a range of carbohydrates, including galactose, glucose, lactose, maltose, salicin, starch and trehalose, but not from arabinose, glycerol, inulin, mannitol, raffinose, sorbitol, sucrose or xylose. In contrast, Japanese isolates did not grow at 45°C or hydrolyse sodium hippurate (Minami et al., 1979; Kitao et al., 1981; Ugajin, 1981). Of course, such differences may reflect the lack of standard- isation in the testing regimes or, indeed, point to heterogeneity in the species composi- tion of the organisms. A comparison of the characteristics of fish-pathogenic streptococci and lacto- bacilli with the results of the comprehensive taxonomy study by Bridge and Sneath
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54 Bacterial Fish Pathogens o O O OH H U + c/:) ^ + + + + + 1 ^ 1 ^ 1 + ^ 1 ^ + CCL 1 + GO GO GO 1 1 + 1 ^ ^ ^ + + + + + + ;^ 1 1 1 1 ;^ ;^ 1 'Eh o O ^ (U >. ^ CO. I 1 + c/:) ^ c/:) ^ + c/:) ^ c/:) ^ 1 + + 1 1 + + 1 1 1 CO. s CO. CO. s 1 1 ^ ^ s 1 + 1 1 1 + 1 1 + 1 1 1 in ^ 1 PH O > ^ 2 0-) ^ ? ^ < pq GO GO I I I I + I + I I I I + I I + + + + ^ + + in in in in in I + ^ ^ ^ ^ ^ I I I I 2 : I I + + ^ + + I \ "A \ ^ \ I oo oo oo I + + ;^ ;^ ;^ i oo oo oo I I ; ^ I ; ^ I ; ^ in in m m m O ^^ ;S ^ ^ u u ^ ^ ^ ^ ^ O O ffi ^ _ _ OH ^ -H ^ O
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Characteristics of the pathogens: Gram-positive bacteria 55 O OH T3 in in m I \ ^ ^ \ I I ;^ + I c/) m \ ^ \ I + + I ;^ I + I + I I I + I + + + m m \ ^ \ I + + I ;^ + + m + + I ;^ + + c/) m I ;^ I + + + I ;^ I + I + I I + I + m in m I ;^ I I ;^ + I ;^ + + c/) m \ ^ \ I + + + ;^ I + C/) C/) C/) + I ;^ I I ;^ I I ;^ + I ^ + + ^ m m -l^ mm I
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