35
will cause similar diseases in Atlantic salmon and rainbow trout. Also, En. faecalis
and En. faecium have been recovered from diseased rainbow trout in South Africa
(Bekker et al. 2011 ), and En. faecalis from farmed fi sh in Taiwan (Young et al.
2012a ). Certain traits of the causal agent(s) have been repeatedly emphasised as
having supposedly taxonomic signifi cance. In particular, the ability to attack blood
has been highlighted. Thus fi sh pathogenic strains have been described, at one time
or another, as either α- (Kusuda et al. 1976 ; Al-Harbi 1994 ) or ß-haemolytic
(Robinson and Meyer 1966 ; Minami et al. 1979 ; Kitao et al. 1981 ; Ugajin 1981 ;
Iida et al. 1986 ) or as non-haemolytic (Plumb et al. 1974 ; Cook and Lofton 1975 ;
Iida et al. 1986 ). Superfi cially, this information could infer heterogeneity among the
pathogens, although some well-established taxa, e.g. Str. agalactiae, contain both
α - and ß-haemolytic strains). Nevertheless, many characteristics are shared by
many of the fi sh pathogens. Yet, there is also some variance in the overall descriptions reported by different groups of workers. 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, raffi -
nose, 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 refl ect the lack of standardisation in the testing
regimes or, indeed, point to heterogeneity in the species composition of the
organisms.
A comparison of the characteristics of fi sh pathogenic streptococci and lactobacilli with the results of the comprehensive taxonomy study by Bridge and Sneath
( 1983 ) revealed that the isolates, described by Hoshina et al. ( 1958 ), Robinson and
Meyer ( 1966 ), Boomker et al. ( 1979 ), Minami et al. ( 1979 ), Cone ( 1982 ) and Kitao
( 1982a ), approximated to En. faecalis, Str. equinus, Str. lactis, Str. casselifl avus,
pediococci and the ‘aerococcal’ group, respectively. Subsequently, some of these
taxa have been re-classifi ed in the genus Enterococcus . However, the organisms
recovered by Kusuda et al. ( 1976 ), Onishi and Shiro ( 1978 ), Minami ( 1979 ), Kitao
et al. ( 1981 ) and Ugajin ( 1981 ) did not match the descriptions of any of the 28 phena
defi ned by Bridge and Sneath ( 1983 ).
With such information, it could readily be assumed from the early literature that
streptococcicosis is a syndrome caused by more than one species. To some extent,
geographical differences have been implied. For example, the South African isolates of Boomker et al. ( 1979 ) have been described as comprising unidentifi ed
Lancefi eld Group D Streptococcus ; Japanese isolates linked with, but not identical
to, En. faecalis and En. faecium [note: the type strain of En. faecium has been determined to be pathogenic to salmonids in laboratory-based infectivity experiments;
Austin, unpublished data] ; whereas American strains approximate to the description of Str. agalactiae (Kusuda and Komatsu 1978 ). It is interesting that isolates
from cases of streptococcicosis in rainbow trout farmed in Italy were originally
linked with En. faecalis and En. faecium (Ghittino and Pearo 1992 ; 1993 ) before
taxonomic re-appraisal, as indicated below.
Gram-Positive Cocci in Chains: The Early Literature
will cause similar diseases in Atlantic salmon and rainbow trout. Also, En. faecalis
and En. faecium have been recovered from diseased rainbow trout in South Africa
(Bekker et al. 2011 ), and En. faecalis from farmed fi sh in Taiwan (Young et al.
2012a ). Certain traits of the causal agent(s) have been repeatedly emphasised as
having supposedly taxonomic signifi cance. In particular, the ability to attack blood
has been highlighted. Thus fi sh pathogenic strains have been described, at one time
or another, as either α- (Kusuda et al. 1976 ; Al-Harbi 1994 ) or ß-haemolytic
(Robinson and Meyer 1966 ; Minami et al. 1979 ; Kitao et al. 1981 ; Ugajin 1981 ;
Iida et al. 1986 ) or as non-haemolytic (Plumb et al. 1974 ; Cook and Lofton 1975 ;
Iida et al. 1986 ). Superfi cially, this information could infer heterogeneity among the
pathogens, although some well-established taxa, e.g. Str. agalactiae, contain both
α - and ß-haemolytic strains). Nevertheless, many characteristics are shared by
many of the fi sh pathogens. Yet, there is also some variance in the overall descriptions reported by different groups of workers. 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, raffi -
nose, 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 refl ect the lack of standardisation in the testing
regimes or, indeed, point to heterogeneity in the species composition of the
organisms.
A comparison of the characteristics of fi sh pathogenic streptococci and lactobacilli with the results of the comprehensive taxonomy study by Bridge and Sneath
( 1983 ) revealed that the isolates, described by Hoshina et al. ( 1958 ), Robinson and
Meyer ( 1966 ), Boomker et al. ( 1979 ), Minami et al. ( 1979 ), Cone ( 1982 ) and Kitao
( 1982a ), approximated to En. faecalis, Str. equinus, Str. lactis, Str. casselifl avus,
pediococci and the ‘aerococcal’ group, respectively. Subsequently, some of these
taxa have been re-classifi ed in the genus Enterococcus . However, the organisms
recovered by Kusuda et al. ( 1976 ), Onishi and Shiro ( 1978 ), Minami ( 1979 ), Kitao
et al. ( 1981 ) and Ugajin ( 1981 ) did not match the descriptions of any of the 28 phena
defi ned by Bridge and Sneath ( 1983 ).
With such information, it could readily be assumed from the early literature that
streptococcicosis is a syndrome caused by more than one species. To some extent,
geographical differences have been implied. For example, the South African isolates of Boomker et al. ( 1979 ) have been described as comprising unidentifi ed
Lancefi eld Group D Streptococcus ; Japanese isolates linked with, but not identical
to, En. faecalis and En. faecium [note: the type strain of En. faecium has been determined to be pathogenic to salmonids in laboratory-based infectivity experiments;
Austin, unpublished data] ; whereas American strains approximate to the description of Str. agalactiae (Kusuda and Komatsu 1978 ). It is interesting that isolates
from cases of streptococcicosis in rainbow trout farmed in Italy were originally
linked with En. faecalis and En. faecium (Ghittino and Pearo 1992 ; 1993 ) before
taxonomic re-appraisal, as indicated below.
Gram-Positive Cocci in Chains: The Early Literature