526
Characteristics of the Pathogen
The taxonomy of the pathogen has had a chequered history, which culminated in the
description of a second species, i.e. V. ordalii. This accommodated strains previously regarded as biotype II of V. anguillarum (Schiewe 1981 ). However, there is
cross reactivity with the LPS of V. anguillarum serogroup O2 and V. ordalii
(Muthiara et al. 1993 ). The complexity in the taxonomic understanding of the
pathogen began with the recognition by Nybelin ( 1935 ) of two biotypes. These were
differentiated on the basis of a few biochemical reactions. A further group, i.e. biotype C, was recognised by Smith ( 1961 ). These biotypes were distinguished, as
follows:
– type A, known as V. anguillarum forma typica , produced indole and acid from
mannitol and saccharose.
– type B, referred to as V. anguillarum forma anguillicida, did not produce indole
or acid from mannitol or saccharose.
– type C, coined as V. anguillarum forma ophthalmica, produced acid from mannitol and saccharose, but did not produce indole.
Two further biotypes, i.e. D and E, were later described, both of which produced
indole, but not acid from mannitol. Biotype D, but not E, produced acid from saccharose. In view of modern thought and approaches on bacterial taxonomy, these
descriptions are inadequate. Nevertheless, they heralded an appreciation of heterogeneity within the species. Type C deserves special mention because this was proposed for Japanese strains derived from rainbow trout, and labelled as V. piscium
var. japonicus (David 1927 ; Hoshina 1956 ). Interestingly, they were originally recognised as dissimilar to V. anguillarum. Alternatively, it must be conceded that the
separate name may have refl ected ignorance of the existence of V. anguillarum as
described by Bergman ( 1909 ). The relationship of these so-called biotypes with V.
ichthyodermis, as described by Wells and ZoBell ( 1934 ), and the organism tentatively assigned as V. anguillicida (Nishibuchi and Muroga 1977 ) needs clarifi cation.
Indeed, the latter was considered to resemble both V. anguillarum and Ali. fi scheri.
The multiplicity of studies of Harrell et al. ( 1976 ), Ohnishi and Muroga ( 1976 ),
Håstein and Smith ( 1977 ), Schiewe et al. ( 1977 ), Baumann et al. ( 1978 ), Kusuda
et al. ( 1979 ), Ezura et al. ( 1980 ), Lee et al. ( 1981 ), Kaper et al. ( 1983 ) and West
et al. ( 1983 ) demonstrated very clearly the heterogeneity within V. anguillarum.
Håstein and Smith ( 1977 ) distinguished two subgroups after a principal components
analysis on data collected for 163 isolates and 28 tests. A similar conclusion, i.e.
two subgroupings, was voiced by Schiewe et al. ( 1977 ), Baumann et al. ( 1978 ),
Ezura et al. ( 1980 ) and Lee et al. ( 1981 ). Of the 50 isolates studied by numerical
taxonomy, Kusuda et al. ( 1979 ) defi ned three groups. These were equated with V.
anguillarum (divided into three subgroups), a group closely related to V. parahaemolyticus, and a cluster considered to have affi nity with V. ichthyodermis. Kaper
et al. ( 1983 ) recognised four homogeneous phena among isolates received as V.
anguillarum. This view was reinforced in a later study by West et al. ( 1983 ). Pazos
10 Vibrios
Characteristics of the Pathogen
The taxonomy of the pathogen has had a chequered history, which culminated in the
description of a second species, i.e. V. ordalii. This accommodated strains previously regarded as biotype II of V. anguillarum (Schiewe 1981 ). However, there is
cross reactivity with the LPS of V. anguillarum serogroup O2 and V. ordalii
(Muthiara et al. 1993 ). The complexity in the taxonomic understanding of the
pathogen began with the recognition by Nybelin ( 1935 ) of two biotypes. These were
differentiated on the basis of a few biochemical reactions. A further group, i.e. biotype C, was recognised by Smith ( 1961 ). These biotypes were distinguished, as
follows:
– type A, known as V. anguillarum forma typica , produced indole and acid from
mannitol and saccharose.
– type B, referred to as V. anguillarum forma anguillicida, did not produce indole
or acid from mannitol or saccharose.
– type C, coined as V. anguillarum forma ophthalmica, produced acid from mannitol and saccharose, but did not produce indole.
Two further biotypes, i.e. D and E, were later described, both of which produced
indole, but not acid from mannitol. Biotype D, but not E, produced acid from saccharose. In view of modern thought and approaches on bacterial taxonomy, these
descriptions are inadequate. Nevertheless, they heralded an appreciation of heterogeneity within the species. Type C deserves special mention because this was proposed for Japanese strains derived from rainbow trout, and labelled as V. piscium
var. japonicus (David 1927 ; Hoshina 1956 ). Interestingly, they were originally recognised as dissimilar to V. anguillarum. Alternatively, it must be conceded that the
separate name may have refl ected ignorance of the existence of V. anguillarum as
described by Bergman ( 1909 ). The relationship of these so-called biotypes with V.
ichthyodermis, as described by Wells and ZoBell ( 1934 ), and the organism tentatively assigned as V. anguillicida (Nishibuchi and Muroga 1977 ) needs clarifi cation.
Indeed, the latter was considered to resemble both V. anguillarum and Ali. fi scheri.
The multiplicity of studies of Harrell et al. ( 1976 ), Ohnishi and Muroga ( 1976 ),
Håstein and Smith ( 1977 ), Schiewe et al. ( 1977 ), Baumann et al. ( 1978 ), Kusuda
et al. ( 1979 ), Ezura et al. ( 1980 ), Lee et al. ( 1981 ), Kaper et al. ( 1983 ) and West
et al. ( 1983 ) demonstrated very clearly the heterogeneity within V. anguillarum.
Håstein and Smith ( 1977 ) distinguished two subgroups after a principal components
analysis on data collected for 163 isolates and 28 tests. A similar conclusion, i.e.
two subgroupings, was voiced by Schiewe et al. ( 1977 ), Baumann et al. ( 1978 ),
Ezura et al. ( 1980 ) and Lee et al. ( 1981 ). Of the 50 isolates studied by numerical
taxonomy, Kusuda et al. ( 1979 ) defi ned three groups. These were equated with V.
anguillarum (divided into three subgroups), a group closely related to V. parahaemolyticus, and a cluster considered to have affi nity with V. ichthyodermis. Kaper
et al. ( 1983 ) recognised four homogeneous phena among isolates received as V.
anguillarum. This view was reinforced in a later study by West et al. ( 1983 ). Pazos
10 Vibrios