Antibiotic Susceptibility Profiles of Aeromonas hydrophila Isolates From Aquaculture Farms and Response to Potential Antibacterial Plant Extracts

Aeromonas spp., which inhabits freshwater and marine water bodies, can be responsible for the diseases and mortalities of many different cultured fishes. In this study, the antibiotic susceptibility profiles of 20 Aeromonas hydrophila strains isolated from diseased freshwater fish cultured in the Red River Delta, Vietnam were categorised as non-wild-type (non-WT) strains or were resistant to at least one antibiotic. Also, in-vitro antibacterial activities of extracts from two local plants against several antibiotic-resistant A. hydrophila strains were done to screen for potential bio-antibiotic materials. The antibiotic susceptibility results showed that 25 % of bacterial strains were resistant to 3–9 antibiotics, 35 % to 2 antibiotics, and 10 % to one antibiotic. Both plants, rose myrtle seed, Rhodomyrtus tomentosa Hassk, 1842, extract and fermented garlic, Allium sativum Linnaeus, 1753, supernatant, showed inhibitory activities against antibiotic-resistant A. hydrophila strains. Furthermore, the R. tomentosa extract and the fermented A. sativum supernatant exhibited significant antibacterial effects to several A. hydrophila strains, namely A. hydrophila CEDMA17.021, CEDMA17.002, CEDMA17.008, and CEDMA17.009 resistant to two or more antibiotics. This study demonstrated multiple resistant profiles of A. hydrophila strains to different antibiotics and the inhibitory activities of R. tomentosa extract and the fermented A. sativum supernatant against antibiotic-resistant A. hydrophila strains. Hence, this study indicates the potential use of bio-antibiotics derived from plants to manage Aeromonas-related infections.