Isolation and identification of indigenous lactic acid bacteria with inhibitory activity against Aeromonas hydrophila in Vinh Long province

Aeromonas hydrophila is a common cause of hemorrhagic disease that seriously harms several economically valuable farmed fish species in Vietnam and worldwide. Therefore, the objective of this investigation was to isolate and identify indigenous lactic acid bacteria (LAB) strains that inhibit the growth of A. hydrophila, causing hemorrhagic illness in farmed striped catfish in Vinh Long province. This finding yielded a total of 45 isolates of LAB from the intestine of healthy pangasius catfish. Using the well diffusion agar method, the results showed that 30 out of 45 isolated LAB strains (66.67%) had antibacterial activity against A. hydrophila. Among them, 10 out of 30 strains (33.33%) had strong activity, 15 out of 30 strains (50%) showed moderate activity, and 5 out of 30 strains (16.67%) exhibited weak activity, with mean inhibition diameters of 18.8 ± 3.52, 12.02 ± 1.32, and 5.89 ± 0.73 mm, respectively. With the exception of lipase activity, the enzyme activities of proteases and amylases were found in strain TMT1. Phylogenetic analysis using the 16S rRNA gene sequence showed that strain TMT1 was identified as Lactobacillus casei. The results of the research indicate that isolate TMT1 may be used to produce probiotics that help prevent pangasius hemorrhagic sickness.