502
Characteristics of the Pathogen
The validity and distinctiveness of Ph. damselae has been confi rmed, with isolates
homogeneous by BIOLOG-GN fi ngerprints and API 20E profi les LPS profi les, but
heterogeneous by ribotyping and serology (4 serogroups were defi ned) (Austin
et al. 1997 ).
Although Love et al. ( 1981 ) did not publish detailed reasons for the dissimilarity
of ‘ V. damsela ’ to other species of Vibrio , they did mention that DNA: DNA hybridisation studies had been completed. Unfortunately, the results were not published.
This situation was corrected by Grimes et al. ( 1984b ), who demonstrated low DNA
homology values with other vibrios. Therefore, it is not surprising that the pathogen
was re-classifi ed out from Vibrio, initially to Listonella (MacDonell et al. 1986 ),
then to Photobacterium, as Photobacterium damsela (Smith et al. 1991 ) and fi nally
corrected to Ph. damselae (Trüper and De’Clari 1997 ).
Diagnosis
Serology Magnetic beads incorporating polyclonal antibodies with an enzyme
immunoassay have found success for the rapid diagnosis of pasteurellosis caused by
Ph. damselae subsp. piscicida, in which the commercial kit had a detection limit of
10
4 cells albeit with a problem of specifi city, i.e. other photobacteria namely Ph.
damselae subsp. damselae and Ph. histaminum , were also detected (Romalde et al.
1999 ).
Box 10.1: Photobacterium damselae subsp. damselae
Cultures comprise facultatively anaerobic Gram-negative, weakly motile (by
one or more unsheathed polar fl agella) rods. Arginine dihydrolase, catalase
and oxidase are produced, but not ß-galactosidase, H 2 S, indole, lysine or ornithine decarboxylase or phenylalanine deaminase. Chitin, DNA, starch and
urea, but not corn oil (lipids) or gelatin, are degraded. The methyl red test and
Voges Proskauer reaction are positive. Nitrates are reduced. Growth occurs in
1–6 % (w/v) but not 0 % or 7 % (w/v) sodium chloride. Acid is produced from
D-glucose, maltose and mannose, but not D-adonitol, arabinose, cellobiose,
dulcitol, erythritol, inositol, lactose, mannitol, melibiose, raffi nose,
L-rhamnose, salicin, D-sorbitol, sucrose, trehalose or D-xylose. Acetate,
citrate and malonate are not utilised. Sensitivity is recorded to the vibriostatic
agent, O/129. The G + C ratio (for one strain) is 43 moles %.
10 Vibrios
Characteristics of the Pathogen
The validity and distinctiveness of Ph. damselae has been confi rmed, with isolates
homogeneous by BIOLOG-GN fi ngerprints and API 20E profi les LPS profi les, but
heterogeneous by ribotyping and serology (4 serogroups were defi ned) (Austin
et al. 1997 ).
Although Love et al. ( 1981 ) did not publish detailed reasons for the dissimilarity
of ‘ V. damsela ’ to other species of Vibrio , they did mention that DNA: DNA hybridisation studies had been completed. Unfortunately, the results were not published.
This situation was corrected by Grimes et al. ( 1984b ), who demonstrated low DNA
homology values with other vibrios. Therefore, it is not surprising that the pathogen
was re-classifi ed out from Vibrio, initially to Listonella (MacDonell et al. 1986 ),
then to Photobacterium, as Photobacterium damsela (Smith et al. 1991 ) and fi nally
corrected to Ph. damselae (Trüper and De’Clari 1997 ).
Diagnosis
Serology Magnetic beads incorporating polyclonal antibodies with an enzyme
immunoassay have found success for the rapid diagnosis of pasteurellosis caused by
Ph. damselae subsp. piscicida, in which the commercial kit had a detection limit of
10
4 cells albeit with a problem of specifi city, i.e. other photobacteria namely Ph.
damselae subsp. damselae and Ph. histaminum , were also detected (Romalde et al.
1999 ).
Box 10.1: Photobacterium damselae subsp. damselae
Cultures comprise facultatively anaerobic Gram-negative, weakly motile (by
one or more unsheathed polar fl agella) rods. Arginine dihydrolase, catalase
and oxidase are produced, but not ß-galactosidase, H 2 S, indole, lysine or ornithine decarboxylase or phenylalanine deaminase. Chitin, DNA, starch and
urea, but not corn oil (lipids) or gelatin, are degraded. The methyl red test and
Voges Proskauer reaction are positive. Nitrates are reduced. Growth occurs in
1–6 % (w/v) but not 0 % or 7 % (w/v) sodium chloride. Acid is produced from
D-glucose, maltose and mannose, but not D-adonitol, arabinose, cellobiose,
dulcitol, erythritol, inositol, lactose, mannitol, melibiose, raffi nose,
L-rhamnose, salicin, D-sorbitol, sucrose, trehalose or D-xylose. Acetate,
citrate and malonate are not utilised. Sensitivity is recorded to the vibriostatic
agent, O/129. The G + C ratio (for one strain) is 43 moles %.
10 Vibrios