engleski

Bacterial flora of rainbow trout larvae and fry (Oncorhynchus mykiss)

To date no results have been published regarding the composition of the bacterial flora in rainbow trout larvae and fry during the first days of their lives. The objective of our work was to follow bacterial flora between the third and the eighth week of their lives. During 35 days of experiment bacterial flora of rainbow trout has been examined, along with following physico-chemical characteristics of water quality as well as it's influence on health. Samples for bacteriological examination were taken from gill, heart and kidney areas and innoculated on the plates. Bacterial colonies were examined macroscopically, slides with Gram staining, and afterwords biochemical tests were performed. For identification, APILAB Plus programme (bio Mérieux, France) was used. Bacterial population of rainbow trout larvae and fry changed in dependence with their age. Physico-chemical characteristics of water ranged within optimal values. Most of bacterial colonies originated from gill isolates (64, 4%), than from heart (21, 8%) and kidney areas (13, 8%). The bacterial flora of larvae in incubator was composed mostly of Gram-positive bacteria (75, 1%), genera: Renibacterium (25%), Lactobacillus (16, 7%), Staphilococcus (16, 7%) and Corynebacterium (16, 7%). The transfer of larvae from incubator into the pools resulted in reducing bacterial flora (66, 7%) after 45 minute stay in the pool. Gram-negative bacteria, which have been represented in larvae in incubator with low percent (24, 9%), after the transfer of larvae to the pools became dominant and represented more than 95% of rainbow trout larvae and fry bacterial flora. Flavobacterium, Acinetobacter and Yersinia were the predominant Gram-negative genera in larvae in incubator, whereas Aeromonas, Pseudomonas, Flavobacterium and Pasteurella were the main isolates from rainbow trout larvae and fry until the end of experiment. Bacterial flora of larvae in incubator mostly consists of Gram-positive bacteria, whereas in rainbow trout larvae and fry in pools Gram-negative bacterial flora prevail.

larva - fry; rainbow trout; bacterial flora; internal organs

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