Comprehensive Characterization of a Novel Bacteriophage, vB_VhaS_MAG7 against a Fish Pathogenic Strain of Vibrio harveyi and Its In Vivo Efficacy in Phage Therapy Trials

Abstract

Vibrio harveyi, a significant opportunistic marine pathogen, has been a challenge to the aquaculture industry, leading to severe economical and production losses. Phage therapy has been an auspicious approach in controlling such bacterial infections in the era of antimicrobial resistance. In this study, we isolated and fully characterized a novel strain-specific phage, vB_VhaS_MAG7, which infects V. harveyi MM46, and tested its efficacy as a therapeutic agent in challenged gilthead seabream larvae. vB_VhaS_MAG7 is a tailed bacteriophage with a double-stranded DNA of 49,315 bp. No genes linked with virulence or antibiotic resistance were harbored in the genome. The phage had a remarkably large burst size of 1393 PFU cell−1 and showed strong lytic ability in in vitro assays. When applied in phage therapy trials in challenged gilthead seabream larvae, vB_VhaS_MAG7 was capable of improving the survival of the larvae up to 20%. Due to its distinct features and safety, vB_VhaS_MAG7 is considered a suitable candidate for applied phage therapy.

Characterization of a Vibriophage Infecting Pathogenic Vibrio harveyi

“…Additionally, R21Y maintained high lytic activity over varying environmental conditions (4-55 • C and pH 4-10). R21Y showed better thermal tolerance than vB_VhaM_pir03 (45 • C) [21], VPMCC5 (45 • C) [50], vB_VhaS_MAG7 (45 • C) [54], V-YDF132 (50 • C) [49], and vB_VhaS-R18L (50 • C) [53] and greater acid tolerance than V-YDF132 (pH 5-11) and vB_VhaS-R18L (pH 6-11). Thus, R21Y can remain stable and exert bactericidal activity in practical applications, suggesting that it is a promising candidate for biological control of V. harveyi disease.…”

Perturbation of Quorum Sensing after the Acquisition of Bacteriophage Resistance Could Contribute to Novel Traits in Vibrio alginolyticus

“…Bacterial virulence was assessed using an in vivo challenge model with gilthead seabream larvae as described previously [ 24 ]. Gilthead Seabream eggs at a similar developmental stage obtained from broodstock and kept in Hellenic Center of Marine Research (HCMR) facilities were utilized.…”