Tracing the Evolutionary Course of Antimicrobial Resistance Genes Mutations in Aeromonas Species from Mugil cephalus and Solea solea

A total of eight isolates of Aeromonas species were isolated from 70 Mugil cephalus (M. cephalus) fish and 30 Solea solea (S. solea) fish samples collected from Lake Manzala in Port Said Governorate, Egypt, with a prevalence of 8%. The isolated strains were identified biochemically and genetically, and addressed to detect the antibiotic susceptibility profiles. From M. cephalus fish, A. hydrophila was recorded with the highest (4/70) isolated strains (5.7%), followed by A. caviae, A. sobria and A. schaberttii (1/70), (1/70), and (1/70) strains, with percentages of 1.4, 1.4, and 1.4%, respectively. While A. veronii was isolated from S. solea fish (1/30) strain (3.3%). The molecular identification of isolated aeromonads by conventional PCR was conducted using 16Sr-RNA for Aeromonas species. Results revealed that all isolates were positive. The genetic determinants revealed 2 acquired antibiotic resistance genes, as bla_TEM and gyrA were represented in all Aeromonas spp. bla_CTX-M gene was detected only in 4 species of Aeromonas species (A. caviae, A. sobria, A. schabertii and A. veronii), and (ereA) gene was detected only in 3 strains of Aeromonas species (A. sobria, A. schaberttii and A. veronii). At the genomic level, our study reveals several key mutations in the gyrA gene of A. caviae, A. veronii, and A. hydrophila, specifically at positions 83 and 87, which are known to associate with fluoroquinolone resistance. The predicted functional impact of QRDR mutations using PROVEAN revealed deleterious score (below -2.5) in A. hydrophila S83L, A. veronii D87N and A. caviae D87Y. These mutations are known to confer fluoroquinolone resistance, while the prediction score was natural in A. sobria E84G (-0.7) associated with unknown significance mutation and A. schubertii L82P (-2.5) which is considered a novel mutation, this has not been previously reported in Aeromonas, making it an interesting candidate for further studies for its implication in gene function.