Abstract
Mortalities of bivalve larvae and spat linked with Vibrio spp. infection have been described in hatcheries since 1959, causing potential development of resistant bacteria. A reliable and sustainable solution to this problem is yet to be developed. Potential treatment of bacterial infection with bacteriophages is gaining interest in aquaculture as a more sustainable option for managing Vibrio spp. infection. This study assessed the effectiveness of bacteriophages (Φ-5, Φ-6, and Φ-7) against pathogenic Vibrio isolates (USC-26004 and USC-26005). These phage isolates were found to belong to the Myoviridae viral family. A total of 212 ORFs of Φ-5 were identified and annotated. The genome of this phage contained putative thymidine kinase and lysin enzyme. During infections with phages, the OD values of the isolates USC-26005 and USC-26004 remained stable at a much lower reading compared to the control after 9 h of incubation. Mortality rate of oyster (Saccostrea glomerata) larvae was 28.2 ± 3.5% in the bacteriophage treatment group, compared to 77.9 ± 9.1% in the bacterial treatment group after 24 h incubation. Findings of this study indicate that lytic phages might be utilized as potential bio-control agents of luminescent bacterial disease in oyster hatcheries.
Highlights
Global oyster production accounted for 31% of total world mollusk production in 2016 [1] and a significant proportion of this output relied on hatchery production [2]
The objectives of this study were, to isolate pathogenic Vibrio spp. and their specific bacteriophages, and to determine the effectiveness of a bacteriophage cocktail composed of these isolated bacteriophages against Vibrio spp. infesting cultures of oyster larvae
Watts et that 90% of bacteria isolated from seawater were resistant to at least one antibiotic and 20% of bacteria al. [32] pointed out that 90% of bacteria isolated from seawater were resistant to at least one antibiotic were resistant to five or more antibiotics
Summary
Global oyster production accounted for 31% of total world mollusk production in 2016 [1] and a significant proportion of this output relied on hatchery production [2]. Bivalve hatcheries are constantly threatened by bacterial diseases [3] and in most cases, members of the genus Vibrio have been identified as significant pathogens in production environments [4]. Since the first description of Vibrio species as the causative agents of disease in bivalve larvae [5], numerous studies have identified pathogenic Vibrio spp., including V. tubiashii [3], V. splendidus biovar II [6], and V. ostreicida [7] associated with infections that have caused major losses for shellfish farmers [8]. Major activities within oyster hatcheries include broodstock holding, spawning induction, rearing and setting of larvae, and the culture and production of live microalgae as a larval food source [2]. Three key vectors for potential Vibrio spp. contamination in these hatcheries include broodstock, microalgae cultures, and seawater supply [9,10].
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