Bivalve
aquaculture is generally influenced by bacterial pathogens that cause high
mortality-related losses in hatcheries. Six bacterial phenotypes had been
previously isolated as the most predominant microorganisms in carpet shell clam
(Tapes decussates) samples collected from natural beds in representative
Egyptian clam fisheries. The main aims of this study were to investigate the
nature of the pathogenic strains that significantly affect clam survival and
test their susceptibility to commercially available antibiotics. Based on their
16S rRNA sequences and some biochemical features, two potent clam pathogens
were emerged; one of which is gram-positive and the other is gram-negative. The
former isolate was identified as Micrococcus luteus and the latter as Vibrio
alginolyticus. Experimental challenges with the two bacterial pathogens
introduced at different initial cell concentrations (2.5 X 104 - 7.5
X 104 cfu ml-1) showed markedly diverse clam mortality
results. However, the pathogenic interaction of M. luteus with clam
survival was generally higher than that of V. alginolyticus. When
introduced at a relatively low initial cell density, the infectious records
of V. alginolyticus were significantly increased
suggesting that the expression of its key virulence
factors is mainly triggered as a response to host contact. Antibiotic
susceptibility tests suggested chloramphenicol and tetracycline as markedly
effective agents that can be used to control the spread of these two bacterial
pathogens in aquaculture applications.
Micrococcus luteus, Vibrio alginolyticus, Tapes decussates, pathogenicity, fisheries and Aquaculture
Journal Section | Articles |
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Authors |
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Publication Date | December 15, 2017 |
Submission Date | June 30, 2017 |
Published in Issue | Year 2017Volume: 34 Issue: 4 |