Acute Hepatopancreatic Necrosis Disease (AHPND is a devasting shrimp disease recognized by the World Organisation for Animal Health (WOAH). Strains of the Vibrio genus were identified as the causative agent of this disease, particularly Vibrio parahaemolyticus (Vp), which produces a binary toxin called PirAB, expressed by the pirA and pirB genes located on a conjugative virulent plasmid (pVA1).
This disease, first reported in China in 2009 and rapidly spreading around the world, was reported in Mexico for the first time in 2013, causing severe economic losses in the shrimp culture.
Overuse of antibiotics has led to antibiotic-resistant bacteria and weakened immune responses, reducing the effectiveness of treatment. In response, phage therapy has emerged as a promising, environmentally friendly, species-specific, and less expensive alternative to treat bacteria due to its lytic capacity to regulate bacterial populations. However, it has been shown that bacteria can develop resistance through various mechanisms, allowing the proliferation of strains with different genotypes, phenotypes, and levels of virulence, favoring species diversification.
In this study, two lytic bacteriophages, which are viruses that infect and kill bacteria, were isolated and purified from shrimp pond samples taken from different locations south of Mazatlán, Sinaloa, with lytic activity against AHPND-causing Vibrio parahaemolyticus (M0904), one of the most virulent strains.
Subsequently, the Vp M0904 strain will be exposed to the bacteriophages, and those with phage resistance will be isolated. The complete genome of the phage-resistant strains will be obtained using whole genome sequencing to identify genotypic changes. Simultaneously, they will be biologically characterized to evaluate the phenotypic changes such as motility, biofilm production, and antibiotic resistance. A comparison of the degrees of virulence between the phage-resistant strains and the wild-type strain will be made by in vivo experiments with P. vannamei juveniles.