Changes in the effectiveness of chlorine treatments during colonization of Salmonella montevideo on tomatoes
2010
Iturriaga, M. H. | Escartin, E. F.
Inactivation of pathogens in produce is an essential approach for mitigating the risk of disease. A study was undertaken to compare the efficacy of chlorine to kill Salmonella Montevideo cells during colonization on the surface of tomatoes. Tomatoes (Lycopersicum esculentum) were spot-inoculated with 100 μL (ca. 8 log cfu) of S. Montevideo. To promote attachment, inoculated fruits were incubated for 90 min at 22C, then washed to remove unattached cells and stored at 30C and 97% relative humidity for up to 10 days. Periodically, tomatoes were treated with chlorine (1000 or 200 mg/L) or water (control). On day 0, treatments with 1000 or 200 mg/L of chlorine, and water reduced the pathogen population by approximately 5.0, 4.5 and 0.4 log cfu/tomato, respectively. The inactivation efficacy of the sanitizers decreased as the storage time elapsed. By the 7th day, the populations recovered from tomatoes treated with water and disinfectants were not significantly different (P < 0.5). This study clearly shows how the effectiveness of chlorine is modified when treatments are applied to tomatoes several days after the contamination with a human pathogen took place. The diminished effect of disinfection treatments suggests that microorganisms colonizing on surfaces become more resistant to germicides, and that biofilms may provide protective sites, or both. The results also reinforce the concept that once contaminated, bacterial pathogens can persist on tomatoes throughout a normal distribution time.
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