I. Dalsgaard et al., IDENTIFICATION OF ATYPICAL AEROMONAS-SALMONICIDA - INTER-LABORATORY EVALUATION AND HARMONIZATION OF METHODS, Journal of applied microbiology, 84(6), 1998, pp. 999-1006
The atypical isolates of Aeromonas salmonicida are becoming increasing
ly important as the frequency of isolation of bacteria belonging to th
is group continues to rise. The primary object of this study was to co
mpare and evaluate the results obtained in various laboratories concer
ning the biochemical identification of atypical Aer. salmonicida befor
e and after standardization of media and methods. Five laboratories ex
amined 25 isolates of Aer. salmonicida from diverse fish species and g
eographical locations including the reference strains of Aer. salmonic
ida subsp, salmonicida (NCMB 1102) and Aer. salmonicida subsp. achromo
genes (NCMB 1110), Without standardization of the methods, 100% agreem
ent was obtained only for two tests: motility and ornithine decarboxyl
ase. The main reason for the discrepancies found was the variation of
the incubation time prior to reading the biochemical reactions. After
standardization, improvement was obtained with the identification; how
ever, disagreement was still observed between the different laboratori
es. These findings demonstrate the difficulties involved in a proper i
dentification of atypical Aer. salmonicida and also that data presente
d in the literature on various strains of Aer. salmonicida are not rea
dily comparable. This paper seems to be the first on standardization o
f microbiological tests for identification of fish pathogens and the r
esults obtained show the need for standardization of methods both with
in and between laboratories.