title: Enhanced recovery of injured Escherichia coli by compounds that degrade hydrogen peroxide or block its formation.
abstract: Escherichia coli LSUFS was injured either by freezing at -10 degrees C or by heating at 57 degrees C for 12 min. Surviving cells were recovered on nonselective tryptone-glucose extract agar and selective violet red bile agar supplemented with compounds that degrade hydrogen peroxide or block its formation. Various concentrations of the following compounds were tested: sodium pyruvate, 3,3'-thiodipropionic acid, catalase, ascorbic acid, potassium permanganate, sodium thioglycolate, dimethylsulfoxide, ethoxyquin, n-propyl gallate, alpha-tocopherol sodium metabisulfite, and ferrous sulfate. Sodium pyruvate and 3,3'-thiodipropionic acid, when added to either medium, significantly (P greater than 0.01) increased recovery of injured cells. More than 90% of the heat-injured cells and 40 to 90% of the freeze-injured cells failed to grow on unsupplemented tryptone-glucose extract agar. Supplementation of violet red bile agar increased recovery, but the counts remained considerably lower than the tryptone-glucose extract agar counts. The repair detection procedure of Speck et al. (M. Speck, B. Ray, R. Read, Jr., Appl. Microbiol. 29:549-550, 1975) was greatly improved by the addition of pyruvate or 3,3'-thiodipropionic acid. However, when this improved repair detection procedure was applied to foods, pyruvate-supplemented media showed some false-positives. We therefore recommend that 3,3'-thiodipropionic acid be used to supplement media in the repair detection procedure.
mesh_terms: D002374:Catalase; D003470:Culture Media; D004926:Escherichia coli / Q000302:isolation & purification / Q000502:physiology*; D005615:Freezing; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000378:metabolism*; D011422:Propionates; D011773:Pyruvates; D019289:Pyruvic Acid
chemical_list: D003470:Culture Media; D011422:Propionates; D011773:Pyruvates; C013298:thiodipropionic acid; D019289:Pyruvic Acid; D006861:Hydrogen Peroxide; D002374:Catalase