Assessment of microbial contamination in various processing rooms using culture-dependent and 16S rRNA methods in a commercial kitchen in eastern China

Abstract

Commercial kitchens, frequently implicated in foodborne illness outbreaks, underscore the importance of studying bacterial communities in these settings. This study analyzed bacterial communities of two cooked food samples and 49 food contact surface samples in a commercial kitchen in eastern China, utilizing traditional bacterial cultivation methods and 16S rRNA sequencing. The cutting room exhibited the highest microbial contamination, with elevated bacterial colony counts on cutting boards and containers, suggesting it as the primary site for potential cross-contamination risks between different foods. Regarding bacterial communities, Coliform levels in refrigerators ranged from 1.0 to 3.0 log₁₀ CFU/cm², which is below sanitary standards. However, E. coli levels on food contact surfaces and cooked foods exceeded microbial limits set by GB1903 and GB 2726 in China. Proteobacteria were predominant at the phylum level across processing rooms, with Moraxellaceae notably prevalent and Pseudomonadaceae dominant in cooked foods at the family level. Source tracking identified food contact surfaces, including countertops, containers in the cutting room, and refrigerators in the cooking room, as primary sources of bacterial contamination in the final cooked foods, contributing 61.62% of contamination. These findings suggest that effective measures should be developed to control bacterial contamination on kitchen food contact surfaces to prevent cross-contamination among different cooked foods.