Survival of Flavobacterium psychrophilum in rainbow trout ( Oncorhynchus mykiss ) serum in vitro

T. Wiklund, Inger Dalsgaard

Research output: Contribution to journalJournal articlepeer-review


Virulent and non-virulent strains of Flavobacterium psychrophilum of different serotypes were examined for survival and growth in non-immune and immune rainbow trout serum, in vitro. A majority of the examined strains consumed complement of non-immune serum, but the complement cascade was not able to cause an immediate (after 3 h incubation) notable reduction in viability of the inoculated cells. After 24 h incubation a more pronounced reduction in the number of viable bacteria was observed in untreated serum as well as in serum heated at 45degrees C. In serum heated at 56degrees C this reduction in cell number was not observed, but an increase in cell number did not occur either. The serum survival of one of the examined strains was different from the others in showing cell multiplication after 24 h incubation in normal as well as heat- treated (45 and 56degrees C) serum. In immune serum no immediate reduction in viability of inoculated cells, of all tested strains, was observed. The number of viable cells showed a slow decrease or remained almost unchanged for up to 72 h post-inoculation in untreated serum, at 5degrees C as well as 15degrees C, In heat-treated serum (45degrees C) the number of viable cells decreased slowly at 5degrees C and 15degrees C for up to 72 h The results suggest that the examined strains were unaffected by the alternative complement reaction present in fish serum as well as by antibodies against F. psychrophilum. However, some unknown component(s) in the fish sera, or lack of nutrients or essential growth factors, inhibited the growth of most of the examined strains in the tested fish sera. (C) 2002 Academic Press.
Original languageEnglish
JournalFish & shellfish immunology
Issue number2
Pages (from-to)141-153
Publication statusPublished - 2002


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