DAO 64:99-106 (2005)  -  doi:10.3354/dao064099

Accumulation and clearance of orally administered erythromycin and its derivative, azithromycin,in juvenile fall Chinook salmonOncorhynchus tshawytscha

William T. Fairgrieve1,*, Cyndy L. Masada2, W. Carlin McAuley2, Mark E. Peterson2,Mark S. Myers2, Mark S. Strom2

1Pacific States Marine Fisheries Commission, 205 South East Spokane Street Suite 100, Portland, Oregon 97202, USA
2Northwest Fisheries Science Center, NOAA Fisheries, 2725 Montlake Boulevard East, Seattle, Washington 98112, USA

ABSTRACT: Fall Chinook salmon Oncorhynchus tshawytscha were fed practical diets medicated with azithromycin (30 mg kg–1 fish for 14 d) or erythromycin (100 mg kg–1 fish for 28 d) either 1, 2, or 3 times beginning 14 d after initiation of exogenous feeding (February) and ending at smoltification (June). Average tissue concentrations of azithromycin increased from 19.0 µg g–1 in fry to 44.9 µg g–1 in smolts, and persisted in the tissues >76 d after treatment ceased. Tissue concentrations of erythromycin were comparatively low, ranging from 0.2 µg g–1 in fry to 10.4 µg g–1 in smolts. Erythromycin was not detectable 21 d post-treatment. Neither antibiotic caused histopathologically significant lesions in the trunk kidney or other organ tissues. The high tissue concentrations and prolonged retention of azithromycin in Chinook may be factors that increase the efficacy of the antibiotic against Renibacterium salmoninarum, compared with erythromycin, particularly in early life history stages before covertly infected fish show clinical signs of disease.


KEY WORDS: Macrolide pharmacokinetics · Bacterial kidney disease · Juvenile · Chinook salmon


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