The search for effective, sustainable alternatives to antibiotics in aquaculture has intensified interest in probiotics, yet the comparative efficacy of host-derived versus commercial probiotic strains remains poorly understood. This study evaluated the probiotic potential of two indigenous gut isolates including a putatively non-virulent strain of Pseudomonas, Pseudomonas aeruginosa PA4 and Bacillus sp.BA4P, previously screened for safety, against commercial Bacillus - and Pseudomonas -based formulations in red tilapia ( Oreochromis sp.) over a 60-day feeding trial. Fish fed the combined indigenous probiotic (PA4 + BA4P) exhibited superior growth performance, feed efficiency, and digestive enzyme activities (protease, lipase, amylase) compared to control and commercial probiotic groups. Enhanced intestinal villus height, goblet cell density, and intraepithelial lymphocyte counts indicated improved gut health and mucosal immunity. Probiotic supplementation also modulated gut microbiota by increasing beneficial bacteria ( Bacillus , Lactobacillus , Pseudomonas ) and suppressing potential pathogens ( Streptococcus , Aeromonas , Vibrio ). Systemic immunity was strengthened, as evidenced by elevated leukocyte counts, serum IgM levels, and reduced hepatic stress markers. Following co-challenge with Aeromonas hydrophila and Streptococcus iniae , the PA4 + BA4P group showed the highest survival rate (75%), significantly outperforming the control (44% survival). These findings demonstrate that host-adapted, multi-strain probiotics confer more benefits in growth, digestive capacity, gut integrity, and disease resistance, offering a promising sustainable strategy for tilapia aquaculture.
Ntakirutimana et al. (Fri,) studied this question.