240
(usually a negative response), fermentative metabolism, catalase and oxidase production (both positive) and acid production from sucrose and xylose (both negative;
recently, acid production from sucrose has been attributed to some isolates [Wiklund
et al. 1992 ]). These tests will result in a provisional identifi cation of Aer. salmonicida (McCarthy 1976 ). In addition, it is recommended that pathogenic isolates
should be examined for degradation of gelatin (positive), starch (positive) and urea
(negative), arginine dihydrolase (positive), gluconate oxidation (negative) and ornithine decarboxylase production (negative). Unfortunately, this apparently simple
state of affairs may be complicated by the increasing presence of ‘atypical’ isolates,
particularly in non-salmonid fi sh. In particular, these may be non- or
slow-pigmenting.
Serodiagnosis Whole cell agglutination is effective with Aer. salmonicida, but
only for smooth (non-auto-agglutinating) colonies (Rabb et al. 1964 ). This is a pity
since the majority of isolates recovered from clinical cases of disease are, in fact,
rough and auto-agglutinating (McCarthy 1976 ). Subsequently, Kawahara and
Kusuda ( 1987 ) reported that FAT was superior to culturing for the diagnosis of
atypical Aer. salmonicida infections in eels. In a comparative study of serodiagnostic techniques, Sakai et al. ( 1986 ) reported that iFAT and the peroxidaseantiperoxidase enzyme immunoassay (PAP) were more sensitive (capable of
detecting 10
3 CFU/ml) than the latex agglutination and co-agglutination techniques.
These required 10
7 CFU/ml for positive results to be recorded. Nevertheless with
latex agglutination and co-agglutination techniques, more (15/15 = 100 %) positive
samples were detected than by iFAT (10/15 = 67 %) or PAP (1/15 = 73 %). We have
successfully married monoclonal antibodies to Aer. salmonicida with ELISA for a
test, which has proven suitable for use on fi sh farms. Indeed, experiments demonstrated that reliable diagnoses were achieved within 30 min (Austin et al. 1986 ). It
is noteworthy that ELISA systems appear to be more sensitive than culturing for the
detection of Aer. salmonicida (Hiney et al. 1994 ). However, a subsequent development has involved the use of polyclonal antibody-coated gold nanoparticles in an
immunoassay, which enabled the specifi c, sensitive (1 × 10
4 CFU/ml) and rapid
[within 45 min] detection of Aer. salmonicida cells in tissues. Here, the clearly
visible red-purple agglutination of the gold particles indicated the presence of the
pathogen (Saleh et al. 2011 ).
Molecular Techniques Molecular techniques have been used with Aer. salmonicida (e.g. Mooney et al. 1995 ; Miyata et al. 1996 ; Oakey et al. 1998 ; Keeling et al.
2013 ). Barry et al. ( 1990 ) suggested that such probes have the potential to detect the
pathogen in environmental and clinical samples. These workers found that specifi c
probes for micro-organisms could be developed, even if only two base pair differences existed in the target sequence. Hiney et al. ( 1992 ) continued with developmental work leading to the isolation of a DNA fragment specifi c to Aer. salmonicida,
which when incorporated into a polymerase chain reaction technique enabled a sensitivity of detection of approximately two cells of Aer. salmonicida. Mooney et al.
( 1995 ) examined the blood from 61 wild Atlantic salmon from 3 rivers in Ireland,
5 Aeromonadaceae Representative (Aeromonas salmonicida)
(usually a negative response), fermentative metabolism, catalase and oxidase production (both positive) and acid production from sucrose and xylose (both negative;
recently, acid production from sucrose has been attributed to some isolates [Wiklund
et al. 1992 ]). These tests will result in a provisional identifi cation of Aer. salmonicida (McCarthy 1976 ). In addition, it is recommended that pathogenic isolates
should be examined for degradation of gelatin (positive), starch (positive) and urea
(negative), arginine dihydrolase (positive), gluconate oxidation (negative) and ornithine decarboxylase production (negative). Unfortunately, this apparently simple
state of affairs may be complicated by the increasing presence of ‘atypical’ isolates,
particularly in non-salmonid fi sh. In particular, these may be non- or
slow-pigmenting.
Serodiagnosis Whole cell agglutination is effective with Aer. salmonicida, but
only for smooth (non-auto-agglutinating) colonies (Rabb et al. 1964 ). This is a pity
since the majority of isolates recovered from clinical cases of disease are, in fact,
rough and auto-agglutinating (McCarthy 1976 ). Subsequently, Kawahara and
Kusuda ( 1987 ) reported that FAT was superior to culturing for the diagnosis of
atypical Aer. salmonicida infections in eels. In a comparative study of serodiagnostic techniques, Sakai et al. ( 1986 ) reported that iFAT and the peroxidaseantiperoxidase enzyme immunoassay (PAP) were more sensitive (capable of
detecting 10
3 CFU/ml) than the latex agglutination and co-agglutination techniques.
These required 10
7 CFU/ml for positive results to be recorded. Nevertheless with
latex agglutination and co-agglutination techniques, more (15/15 = 100 %) positive
samples were detected than by iFAT (10/15 = 67 %) or PAP (1/15 = 73 %). We have
successfully married monoclonal antibodies to Aer. salmonicida with ELISA for a
test, which has proven suitable for use on fi sh farms. Indeed, experiments demonstrated that reliable diagnoses were achieved within 30 min (Austin et al. 1986 ). It
is noteworthy that ELISA systems appear to be more sensitive than culturing for the
detection of Aer. salmonicida (Hiney et al. 1994 ). However, a subsequent development has involved the use of polyclonal antibody-coated gold nanoparticles in an
immunoassay, which enabled the specifi c, sensitive (1 × 10
4 CFU/ml) and rapid
[within 45 min] detection of Aer. salmonicida cells in tissues. Here, the clearly
visible red-purple agglutination of the gold particles indicated the presence of the
pathogen (Saleh et al. 2011 ).
Molecular Techniques Molecular techniques have been used with Aer. salmonicida (e.g. Mooney et al. 1995 ; Miyata et al. 1996 ; Oakey et al. 1998 ; Keeling et al.
2013 ). Barry et al. ( 1990 ) suggested that such probes have the potential to detect the
pathogen in environmental and clinical samples. These workers found that specifi c
probes for micro-organisms could be developed, even if only two base pair differences existed in the target sequence. Hiney et al. ( 1992 ) continued with developmental work leading to the isolation of a DNA fragment specifi c to Aer. salmonicida,
which when incorporated into a polymerase chain reaction technique enabled a sensitivity of detection of approximately two cells of Aer. salmonicida. Mooney et al.
( 1995 ) examined the blood from 61 wild Atlantic salmon from 3 rivers in Ireland,
5 Aeromonadaceae Representative (Aeromonas salmonicida)