Survival of Salmonella on Tomatoes Stored at High Relative Humidity, in Soil, and on Tomatoes in Contact with Soil

Abstract

Salmonellosis has been linked to the consumption of several types of raw fruits and vegetables, some of which may have been contaminated with Salmonella before harvesting. The objectives of this study were to investigate water and soil as reservoirs of Salmonella for the contamination of mature green tomato fruits. Salmonella survived for at least 45 days in inoculated moist soil. The population of Salmonella on tomatoes in contact with soil increased by 2.5 log10 CFU per tomato during storage for 4 days at 20 degrees C and remained constant for an additional 10 days. The number of cells inoculated on tomatoes decreased by approximately 4 log10 CFU per tomato during storage for 14 days at 20 degrees C and 70% relative humidity. Fruits in contact with inoculated soil for 1 day at 20 degrees C harbored Salmonella only near or on the skin surface. More Salmonella cells were observed in stem scar and subsurface areas of tomatoes as the time of storage increased. PCR fingerprinting revealed that among five Salmonella serotypes in the inoculum, Salmonella Montevideo was the most persistent on tomatoes in contact with inoculated soil and on spot-inoculated tomatoes, followed by Salmonella Poona and Salmonella Michigan. The results of this study demonstrate that an enhanced green fluorescent protein marker can be used to detect cells and monitor the growth of Salmonella in the presence of other microorganisms. Observations on the infiltration of Salmonella into tomato tissues support the contention that preharvest contact of produce with contaminated water or soil exacerbates problems associated with the postharvest removal of pathogens or their accessibility to treatment with sanitizers.

Colonization of Tomatoes by Salmonella Montevideo Is Affected by Relative Humidity and Storage Temperature

“…We used a single strain of Salmonella Montevideo, whereas Guo et al (12) tested a mixture of five serotypes of Salmonella enterica, including the Salmonella Montevideo strain used herein. In the Guo et al (12) study, Salmonella Montevideo was the most resistant strain, which supports the present results. The pathogen behavior could also be influenced by the grade of tomato ripeness (red vs. green); however, Wei et al (26) found that the ripeness of wounded tomatoes had no apparent effect on Salmonella Montevideo populations after 24 h at 25ЊC.…”

Survival and Transmission ofSalmonella entericaSerovar Typhimurium in an Outdoor Organic Pig Farming Environment

“…A generally high fecal contamination level was also evident from detection of a high level of E. coli organisms (3 to 7 log 10 CFU g Ϫ1 ) in the paddock compared to the levels after normal application of pig slurry (3 log 10 CFU g Ϫ1 soil) (15). Other studies have reported recovery of Salmonella from soil several months after inoculation, most likely due to different experimental conditions and higher inoculation doses, e.g., 5 log CFU g Ϫ1 (22,28,38,39). E. coli has been reported to a have a survival rate similar to Salmonella, thus providing a good indicator of decimation of Salmonella (38,41).…”

Microbiological quality of organic vegetables produced in soil treated with different types of manure and mineral fertilizer

“…This concern is directed to Salmonella spp. (24,27,40,47,49) and E. coli O157:H7, because cattle is its main reservoir, explaining the risk of transmission by manure (22,34,43,50).…”