Kitchen Sponges as Reservoirs of Foodborne Pathogens: Microbial Growth Dynamics, Surface Cross-Contamination, and...

Foodborne pathogens pose a persistent risk to public health, with domestic environments representing a major but often underestimated source of contamination. In this study, we investigated the survival, proliferation, and transfer potential of Salmonella Enteritidis, Escherichia coli, and Staphylococcus aureus in kitchen sponges harboring an established core microbiota. Using culture-based, metagenomic, and fluorescence in situ hybridization approaches in combination with confocal laser scanning microscopy, we examined pathogen persistence, desiccation tolerance, cross-contamination potential, and spatial microbial organization over 14 days. All three pathogens persisted within the sponge matrix for at least 2 weeks, even at very low initial populations (approximately 2,5 log₁₀ colony-forming units (CFU) per sponge section). Escherichia coli and Salmonella Enteritidis rapidly established stable populations reaching approximately 9 log CFU per sponge section, whereas S. aureus showed limited growth of approximately 4 log CFU per sponge section, indicating species-specific interactions with the resident microbiota. Notably, pathogen populations remained stable after 3 days of desiccation, confirming the role of sponges as long-term microbial reservoirs. Contact between colonized sponges and surfaces under mild pressure resulted in transfer of up to 5 log CFU to contacted surfaces, highlighting realistic domestic transmission pathways. Sensory changes such as odor or discoloration were not correlated with microbial load, indicating that visual assessment is unreliable for sponge replacement decisions. These results underscore the role of kitchen sponges as critical microbial reservoirs in households and emphasize the need for regular sponge replacement or the use of alternative cleaning utensils. The standardized sponge model developed in this study provides a valuable platform for evaluating sanitation strategies and for understanding microbial interactions relevant to domestic hygiene and public health.