A broad-spectrum broth rapidly and completely repairing the sublethal injuries of Escherichia coli caused by freezing and lactic acid alone or in combination for accurate enumeration

Abstract

Pathogenic and spoilage bacteria undergo various stresses during food preservation and processing, leading to sublethal injuries. This emphasizes the need for a versatile repair broth. Furthermore, the broth should quickly revive all sublethal cells within 20 min to prevent the proliferation of intact cells for accurate counting. For this purpose, we developed a new repair medium called ERBMn in this study. After systematically examining various factors affecting sublethal injuries in both Escherichia coli K-12 and O157:H7, we identified the freezing and thawing (FT) treatment that resulted in the highest sublethal ratio for each strain. Then, five treatments were used to induce various numbers, types, and degrees of sublethal injuries for both strains: FT, lactic acid (LA), pretreatment with LA followed by FT, concurrent exposure to LA and FT, and pretreatment with FT followed by LA. Our results demonstrated that ERBMn rapidly and completely recovers all sublethal injuries within 20 min. Additionally, we confirmed no observable proliferation after a 20-min incubation in ERBMn. To the best of our knowledge, ERBMn is the first broad-spectrum repair broth for precise enumeration. It is expected to become the preferred repair broth for accurately quantifying E. coli in food for food safety.