Properties of Probiotics Kocuria SM1 and Rhodococcus SM2 Isolated from Fish Guts

Area of Science:

• Microbiology
• Aquatic Animal Health
• Probiotics

Background:

• The intestinal microbiota plays a crucial role in fish health and nutrition.
• Probiotics offer a sustainable alternative to antibiotics in aquaculture.
• Characterizing novel probiotic strains is essential for their effective application.

Purpose of the Study:

• To characterize Kocuria SM1 and Rhodococcus SM2 probiotics isolated from rainbow trout.
• To assess their tolerance to gastrointestinal conditions and antimicrobial activity.
• To evaluate their potential as functional probiotics in aquaculture.

Main Methods:

• Isolation and characterization of bacterial strains from rainbow trout intestine.
• Assessment of growth under various temperature, salinity, and pH conditions.
• Enzyme profiling using API-ZYM system and antimicrobial activity testing against selected pathogens.
• Determination of resistance to antimicrobial agents.

Main Results:

• Kocuria SM1 and Rhodococcus SM2 demonstrated robust growth across wide ranges of temperature (4-37°C, 45°C for SM1), salinity (0-20% NaCl), and pH (2-11).
• Both strains survived simulated gastrointestinal conditions (pepsin and pancreatin).
• Secondary metabolites from both strains inhibited pathogenic bacteria; Rhodococcus SM2 showed broader activity, including against multi-drug-resistant human pathogens like Escherichia coli and Staphylococcus aureus.
• Rhodococcus SM2 exhibited resistance to penicillin and sulphatriad, while Kocuria SM1 was resistant to sulphatriad.

Conclusions:

• Kocuria SM1 and Rhodococcus SM2 are robust probiotics with potential for aquaculture applications due to their wide environmental tolerance and antimicrobial properties.
• Extracellular enzymes produced by these probiotics may aid in fish digestion.
• Rhodococcus SM2's activity against multi-drug-resistant pathogens highlights its significant potential for novel therapeutic applications.