When a disease occurs in aquaculture, it affects local economic and social development and usually uses antibiotics to control disease. However, the use of antibiotics destroys the balance of microorganisms in the fish gut and dysbiosis can cause diseases caused by the multiplication of pathogens. Probiotics are known to help balance the composition of intestinal microflora, inhibit the growth of pathogens, and have a positive impact on growth and survival. This study investigated the effects of probiotics on antibiotic therapy and recovery steps after antibiotic treatment of fish.
There were four different treatment of feeds were used in this study including Control (control feed for 3weeks), AMX (AMX; amoxicillin feed for 3weeks), AMX/CON (amoxicillin feed for 2 weeks after E. piscicida EET52 107 CFU/fish 2 times challenge. After that, control feed for 1 week), and AMX/PRO (amoxicillin feed for 2 weeks after E. piscicida EET52 107 CFU/fish 2 times challenge. After that, probiotic feed for 1 week). Probiotics feed were made 108 CFU/g of Lactoccocus lactis supsp. lactis strain WFLU12 and 40 mg/kg bw/day of amoxicillin feed were made. Metagenomic sequencing was conducted on twelve of fish gut mucus samples.
Our results confirmed that the majority of operational taxonomic units (OTUs; 97% sequence similarity) in all compartment consisted primarily of Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria. Enterobacteriaceae showed an increasing pattern in the treatment 2, 3 and 4 where antibiotics were administered. Addition of probiotics led to an increase in microbial diversity, leading to an increase in Firmicutes phylum and a decrease in the strain of Enterobacteriaceae. Lactococcus lactis was significantly increased in AMX / PRO.Interestingly, when comparing the total number of reads, S. parauberis was significantly (P < 0.05) reduced in AMX and AMX / PRO than in CON. Edwardsiella, the most abundant genus, tended to be reduced by amoxicillin and showed increased patterns in AMX / CON and AMX / PRO. However, citrobacter increased in AMX and AMX / CON. Vibrio showed a tendency to decrease in AMX and AMX / PRO compared to CON. After amoxicillin treatment, treatment with probiotics will inhibit colonization of fish pathogens in fish gut.