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

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 poses a serious threat to tilapia populations. Probiotics have emerged as a potentially safe preventive measure against 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 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: spp., and were examined to assess their antibacterial properties, hemolytic patterns, and antibiotic resistance genes. We used the specific primers , , , , , , , and that were used for antibiotic resistance gene detection. probiotic efficacy was evaluated by administering probiotic candidates in tilapia feed at a concentration of 1 × 10 colonies/mL/50 g of feed over a 60-day maintenance period. Resistance to infection was observed for 14 days after the challenge test.

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

Conclusion: Probiotics, particularly , and spp., enhance growth and resistance against 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.