Comparative In vitro Evaluation of Widely Used Aquaculture Disinfectants Against Major Marine Bacterial Fish...

Effective disinfection is a critical component of aquaculture biosecurity. The present study evaluated in vitro efficacy of eight commonly used disinfectants [Chloramine-T, benzalkonium chloride (BKC), iodophor, formalin, sodium hypochlorite, hydrogen peroxide (H₂O₂), potassium permanganate (KMnO4), and glutaraldehyde] against three major marine pathogens, viz. Streptococcus agalactiae, Photobacterium damselae, and Vibrio vulnificus. Multiple evaluations were performed, including determination of minimum inhibitory concentration (MIC), time-kill kinetics, effective concentration, influence of organic load, and an integrated activity scoring system. Sodium hypochlorite and BKC had the maximum and minimum MICs, respectively, across all three species. The least coefficient of variation % in MIC across different species was shown by BKC (34.4%). Iodophor and Chloramine-T achieved a ≥ 5 log₁₀ reduction in all pathogens within 10 min at their MIC level. Formalin could not achieve the desired results even at 16-fold higher MIC values, showing its unsuitability for rapid surface disinfection protocols. All disinfectants showed reduced efficacy even at an organic load level of 0.5%. Integrated scoring system graded iodophor and BKC as the most effective disinfectants (> 80% of total score), making them strong candidates for aquaculture disinfection programmes. Collectively, the findings serve as the reference for adopting effective biosecurity practises against bacterial pathogens in marine/estuarine aquaculture.