Effectiveness of disinfectant MA-T against Escherichia coli in various growth media was demonstrated by minimal inhibitory concentration (MIC). MIC of MA-T in (DM+1/100 volume of LBG [Luria-Bertani medium with 0.4% glucose]) at pH 6.5 and pH 8.5 was 2.5 μg/mL, and that in 100%LBG at pH 6.5 and pH 8.5 was 7.5 μg/mL and 10 μg/mL, respectively. MA-T is not markedly affected by organic materials or pH. MIC of HClO in DM+1/100LBG at pH 6.5 and pH 8.5 was 7.5 μg/mL and 12.5 μg/mL, respectively, but MIC in rich medium (100%LBG) at pH 6.5 and pH 8.5 was 300 μg/mL and 500 μg/mL, respectively, indicating that HClO does not affect bacteria because of preferential reaction with biological materials contained in LBG, with minimal difference at varying pH. Growth of E. coli as monitored in aerobic shaking culture in LBG was dramatically reduced by adding 25 μg/mL MA-T, but growth was not affected by 100 μg/mL HClO (pH 6.5) or NaClO (pH 8.5). The CFU/mL of E. coli in aerobic standing culture in LBG declined linearly with incubation time on a logarithm chart after addition of 25 μg/mL MA-T. Viability was not affected by the addition of 100 μg/mL HClO (pH 6.5) or NaClO (pH 8.5). In conclusion, bactericidal effect of MA-T against E. coli is minimally affected by biological substances at different pH values (pH 6.5 or 8.5), but bactericidal effect of both HClO (pH 6.5) and NaClO (pH 8.5) is completely abolished by biological substances.