Construction and Characterization of an Aeromonas hydrophila Multi-Gene Deletion Strain and Evaluation of Its Potential as a Live-Attenuated Vaccine in Grass Carp

Abstract

Aeromonas hydrophila is an important pathogen that causes motile Aeromonas septicemia (MAS) in the aquaculture industry. Aerolysin, hemolysin, serine protease and enterotoxins are considered to be the major virulence factors of A. hydrophila. In this study, we constructed a five-gene (aerA, hly, ahp, alt and ast) deletion mutant strain (named Aeromonas hydrophila five-gene deletion strain, AHFGDS) to observe the biological characteristics and detect its potential as a live-attenuated vaccine candidate. AHFGDS displayed highly attenuated and showed increased susceptibility to fish blood and skin mucus killing, while the wild-type strain ZYAH72 was highly virulent. In zebrafish (Danio rerio), AHFGDS showed a 240-fold higher 50% lethal dose (LD50) than that of the wild-type strain. Immunization with AHFGDS by intracelomic injection or immersion routes both provided grass carp (Ctenopharyngodon idella) significant protection against the challenge of the strain ZYAH72 or J-1 and protected the fish organs from serious injury. Further agglutinating antibody titer test supported that AHFGDS could elicit a host-adaptive immune response. These results suggested the potential of AHFGDS to serve as a live-attenuated vaccine to control A. hydrophila infection in aquaculture.

Pharmacoprophylaxis of experimental aeromonosis of carp in the conditions of farms in the Krasnodar region

“…Bacteriological studies carried out during the experiment showed that on the 5th day there were no significant differences between the fish of the experimental and control groups (Table 1). The control reisolation on the 10th day after infection showed that the contamination of the parenchymal organs of the fish of the control group remained at a high level (1.2x10 7 -8.4x10 7 ), while in the experimental group a pronounced decrease in contamination was noted (2.0x10 5 -5.2x10 6 ) or even absence of increase compared to the first reisolation (1.9x10 7 -3.5x10 7 ).…”

“…Both in natural ecosystems and in aquaculture conditions, fish are often exposed to mass infections with aeromonosis, which can cause significant economic damage to fish farms [7,8].…”

A Review of Bacterial Co-Infections in Farmed Catfish: Components, Diagnostics, and Treatment Directions

“…A catfish-derived vAh strain selected for resistance to two antibiotics demonstrated significant protection in channel catfish and Nile tilapia when IP-injected, resulting in 86–100% protection relative to naïve fish [ 49 ]. Attenuated vaccines to protect fish from vAh were generated by selecting for antibiotic resistance [ 50 ] or generating attenuated vAh via multiple gene deletions [ 51 ]. An attenuated vAh strain resistant to both novobiocin and rifampicin was used to vaccinate channel catfish by IP, resulting in 100% protection against the parent vAh strain with evidence for a strong antibody-mediated response and induction of Na(+)/K(+) ATPase α subunit, hepcidin, interleukin-1β, and lysozyme c within the anterior kidney in vaccinated fish relative to naïve fish [ 50 ].…”

“…The mutant strain yielded an RPS of 70 or 75% when fish were vaccinated by immersion and subsequently challenged by two different vAh strains. An RPS of 75 or 85% was obtained when fish were vaccinated by intracelomic injection and challenged by vAh strains [ 51 ].…”

Streptomyces enissocaesilis L-82 has broad-spectrum antibacterial activity and promotes growth for Carassius auratus

“…When water pollution, high stocking density, and improper breeding operations increase the risk of sepsis outbreaks (Azzam-Sayuti et al 2021 ). The disease can cause swelling, necrosis, ulceration, and hemorrhagic septicemia in fish tissues, and the incidence rate is fast, and the mortality rate is also very high, causing huge economic losses to fish farmers (Li et al 2021 ). Therefore, the prevention and control of such diseases is the focus of prevention and control in fish aquaculture.…”