Antibiotic resistance gene-free probiont administration to tilapia for growth performance and Streptococcus agalactiae resistance

Research (Published online: 25-12-2023)

16. Antibiotic resistance gene-free probiont administration to tilapia for growth performance and Streptococcus agalactiae resistance

Mira Mawardi, Agustin Indrawati, Angela Mariana Lusiastuti, and I Wayan Teguh Wibawan

Veterinary World, 16(12): 2504-2514

Mira Mawardi: Division of Medical Microbiology, School of Veterinary Medicine and Biomedical Sciences, IPB University, Jl. Agatis Kampus IPB Dramaga Bogor, Jawa Barat, 16680 Indonesia; Government of Indonesia Ministry of Marine Affairs and Fisheries, Main Center for Freshwater Aquaculture - Ministry of Marine Affairs and Fisheries, Jl. Selabintana No. 37, Selabatu, Kec. Cikole, Kota Sukabumi, Jawa Barat 43114, Indonesia.

Agustin Indrawati: Division of Medical Microbiology, School of Veterinary Medicine and Biomedical Sciences, IPB University, Jl. Agatis Kampus IPB Dramaga Bogor, Jawa Barat, 16680 Indonesia.

Angela Mariana Lusiastuti: Research Center for Veterinary Sciences. National Research and Innovation Agency, KST BRIN Soekarno Cibinong Bogor, 16911, Jawa Barat, Indonesia.

I Wayan Teguh Wibawan: Division of Medical Microbiology, School of Veterinary Medicine and Biomedical Sciences, IPB University, Jl. Agatis Kampus IPB Dramaga Bogor, Jawa Barat, 16680 Indonesia.

Background and Aim: The rapid development of aquaculture as a major food sector is accompanied by challenges, including diseases that affect tilapia farming worldwide. One such infectious disease caused by Streptococcus agalactiae poses a serious threat to tilapia populations. Probiotics have emerged as a potentially safe preventive measure against S. agalactiae infection. However, antimicrobial resistance from antibiotic-resistant bacteria remains a concern because it can lead to the spread of resistant bacteria and serve as a reservoir of antibiotic-resistant genes in fishes and the surrounding environment. This study aimed to identify candidate probiotic bacteria capable of promoting tilapia growth, providing resistance to S. agalactiae infection, devoid of potential pathogenicity, and free from antibiotic resistance genes. Subsequently, the performance of these probiotic candidates in tilapia was evaluated.

Materials and Methods: Lactococcus garvieae, Priestia megaterium, Bacterium spp., Bacillus megaterium, Bacillus subtilis, and Bacillus pumilus were examined to assess their antibacterial properties, hemolytic patterns, and antibiotic resistance genes. We used the specific primers tetA, tetB, tetD, tetE, tetO, tetQ, ermB, and qnrS that were used for antibiotic resistance gene detection. In vivo probiotic efficacy was evaluated by administering probiotic candidates in tilapia feed at a concentration of 1 × 106 colonies/mL/50 g of feed over a 60-day maintenance period. Resistance to S. agalactiae infection was observed for 14 days after the challenge test.

Results: Lactococcus garvieae, P. megaterium, and Bacterium spp. were identified as promising probiotic candidates among the bacterial isolates. On the other hand, B. megaterium, B. subtilis, and B. pumilus carried resistance genes and exhibited a β hemolytic pattern, rendering them unsuitable as probiotic candidates. The selected probiotic candidates (L. garvieae, P. megaterium, and Bacterium spp.) demonstrated the potential to enhance tilapia growth, exhibited no pathogenic tendencies, and were free from antibiotic resistance genes. Supplementation with L. garvieae and Bacterium spp. enhanced tilapia resistance to S. agalactiae infection, whereas P. megaterium supplementation showed an insignificant survival rate compared with controls after the challenge test period.

Conclusion: Probiotics, particularly L. garvieae, P. megaterium, and Bacterium spp., enhance growth and resistance against S. agalactiae infection, without harboring antibiotic resistance genes. Selecting probiotic candidates based on antibiotic resistance genes is essential to ensure the safety of fish, the environment, and human health.

Keywords: Bacterium, Lactococcus garvieae, Priestia megaterium, Probiotic, Streptococcus agalactiae, Tilapia.