Synergistic combination of malic acid with sodium hypochlorite impairs biofilm of Cronobacter sakazakii

The current study determined the antibacterial and antibiofilm activity of six organic acids including acetic acid, citric acid, formic acid, tartaric acid, malic acid and maleic acid along with different chemicals (disinfectants, surfactants and chelating agents) either alone or in a combination of organic acid with chemicals against C. sakazakii. All the organic acids and only three chemicals viz., EDTA, NaCl, NaOCl were found to possess antiCronobacter activity and were evaluated for antibiofilm efficacy. All the agents tested for antibiofilm activity were quite effective against formation of biofilm as well as prefomed mature biofilms. Subtractive screening based on antibiofilm activity of different combinations revealed malic acid (0.0625 mol l- 1) with NaOCl (0.00004 mol l- 1) as the most effective combination with fractional inhibitory concentration index (FICI) of 0.38. Biofilm microstructures were rarely observed after treatment as revealed by light microscopy and SEM analysis and a reduction of 7.06 +/- 0.40 log CFU ml-1 in viable cell counts as compared to control groups. The findings indicate that combination of malic acid with NaOCl has synergistic effect and may have implications in its usage in eradication of C. sakazakii biofilms from abiotic surfaces in production plant and clinical settings.