Role of cellulose in protecting Shiga toxin producing Escherichia coli against oxidative and acidic stress

This study assessed the role of cellulose in protecting Shiga toxin-producing Escherichia coli (STEC) against environmental stress. Cellulose producing STEC strain 19B (O5:H-) and 49B (O103:H2) as well as their cellulose deficient derivates (19D and 49D) were subjected to oxidative (10, 20 and 30 mM H2O2) and acidic (pH 3.0, 3.5 and 4.5) stress. Approximately 4.25, 2.46 or 1.74 log CFU ml−1 of the 19B cells survived a 2.5-h treatment with 10, 20 and 30 mM H2O2, respectively, while none of the 19D cells (8.02 logs) survived the same treatments. The population of 49D decreased from 7.70 to <0.60 log CFU ml−1, whereas that of 49B decreased from 7.70 to 2.47 log CFU ml−1 by a 2-h treatment with 30 mM H2O2. Approximately 2.63 log CFU ml−1 of the 19B cells survived at pH 3.0 for 1 h and 4.75 log CFU ml−1 of the 49B cells survived at pH 3.0 for 1.5 h, but the 19D and 49D cells did not survive these treatments. Results indicated that cellulose protected the selected STEC strains against oxidative treatments with 10–30 mM of H2O2 and acidic treatments at pH 3.0–3.5.