Survival of Salmonellae on and in Tomato Plants from the Time of Inoculation at Flowering and Early Stages of Fruit Development through Fruit Ripening

Abstract

The fate of salmonellae applied to tomato plants was investigated. Five Salmonella serotypes were used to inoculate tomato plants before and after fruits set, either by injecting stems with inoculum or brushing flowers with it. Ripe tomato fruits were subjected to microbiological analysis. Peptone wash water, homogenates of stem scar tissues, and homogenates of fruit pulp were serially diluted and plated on bismuth sulfite agar before and after enrichment. Presumptive Salmonella colonies were confirmed by serological tests, PCR assay using HILA2 primers, and enterobacterial repetitive intergenic consensus PCR. Of 30 tomatoes harvested from inoculated plants, 11 (37%) were positive for Salmonella. Of the Salmonella-positive tomatoes, 43 and 40%, respectively, were from plants receiving stem inoculation before and after flower set. Two of eight tomatoes produced from inoculated flowers contained Salmonella. Higher percentages of surface (82%) and stem scar tissue (73%) samples, compared to pulp of Salmonella-positive tomatoes (55%), harbored the pathogen. Of the five serotypes in the inoculum, Montevideo was the most persistent, being isolated from tomatoes 49 days after inoculation, and Poona was the most dominant, being present in 5 of 11 Salmonella-positive tomatoes. Results suggest that Salmonella cells survive in or on tomato fruits from the time of inoculation at flowering through fruit ripening. Tomato stems and flowers are possible sites at which Salmonella may attach and remain viable during fruit development, thus serving as routes or reservoirs for contaminating ripened fruit.

Differential interaction of Salmonella enterica serovars with lettuce cultivars and plant-microbe factors influencing the colonization efficiency

“…For example, gfp-tagged strains of S. enterica colonized the interior of tomato plants when grown hydroponically (Guo et al, 2001;Guo et al, 2002) and various S. enterica serovars were able to colonize Medicago sativa and other leguminous plants endophytically and epiphytically (Dong et al, 2003;Wang et al 2006). Also, an avirulent strain of S. enterica serovar Typhimurium colonized carrots and radishes which were grown on a field treated with S. enterica serovar Typhimurium-contaminated composted manure or irrigation water (Islam et al, 2004).…”

Investigation of Possible Situation of Internalization of Salmonella Enteritidis in Tomato Fruits and Bacterial Survival during Tomato Plant Cultivation

“…However, the route of contamination remains vague. It was shown that S. enterica can contaminate entire tomato plants following direct root inoculations in a hydroponic system , and S. enterica was observed to contaminate tomato fruits by direct inoculation of flowers (Guo et al, 2001). These results suggest that Salmonella contamination of tomatoes can occur during cultivation.…”

“…Guo et al (2001) reported that brushing tomato flowers with a fivestrain cocktail of S. enterica (serovar Enteritidis, Harford, Michigan, Montevideo, and Poona) resulted in contamination of 25% of ripe fruits. The present result, however, showed that S. Enteritidis counts were below the detection limit (< 0.3 MPN/g) in the edible parts of tomato and calyces (Table 3).…”

Comparison of Phage-Based Magnetoelastic Biosensors with Taqman- Based Quantitative Real-Time PCR for the Detection of Salmonella typhimurium Directly Grown on Tomato Surfaces

“…Since the most predominant place for harboring Salmonella in or on tomatoes has been found to be the outer surface (82%) [12], the ME biosensor method has been applied directly to the tomato surfaces without any further sample preparation. S. typhimurium was inoculated and grown directly on the tomato surfaces in order to compare the ME biosensor method with Q-PCR.…”