In vitro evaluation of antimicrobial activity of Benzalkonium chloride and Glutaraldehyde combination (REMOVE) on waters with different salinities

The stability of disinfectants in water is one of the desirable features of these compounds. The physicochemical conditions of water, such as hardness, pH, salinity, and etc., can affect the performance of disinfectants. The present study was designed to evaluate the effect of different water salinities on the antimicrobial properties of commercial REMOVE disinfectant (combination of benzalkenium chloride and glutaraldehyde) against some true and opportunistic pathogenic microorganisms of fish. First, four bacterial strains including Streptococcus iniae, Aeromonas Salmonisida, Vibrio Harveyi, and Streptococcus agalactiae, and three fungi including Aspergillus niger, Fusarium oxysporum, and Saprolgenia spp. were selected and cultured on appropriate condition. Then, 1-3106 dilutions of each microorganism were prepared and REMOVE activity was evaluated (in two concentrations of 20 ppm and 10 ppm) in different salinity concentrations (0, 20, 40 ppt) in two time periods of 20 and 40 min. The viability of the studied microorganisms was assessed by disc diffusion and in a liquid medium under laboratory conditions. There was no significant differences in viability of studied microorganisms between the two concentrations of 10 and 20 ppm in different salinities (p>0.05). However, increasing the salinity to 20 and 40 ppt had a significant effect on the viability of the microorganisms in comparison with 0 ppt salinity (p<0.05). At 40 ppt concentrations, the highest amount of CFU/ml was observed in V. harveyi. Although disinfectant is able to reduce the population of microorganisms in different salinities, however this reduction is not very effective compared to 0 ppt concentration. Therefore, based on the results of the present study, it is possible that this disinfectant can be used to reduce the population of microbes in salty waters, but this reduction in practice alone will not be effective enough and requires the use of other controlling programs besides.