Purpose: To investigate if soil and humidity conditions alter Salmonellasurvival on plastic tomato collection totes.
Methods: Five produce-related, nalidixic acid-resistant strains of Salmonella entericawere standardized and mixed before being added to water containing 5% horse serum, 5% soil, or a mix of 5% horse serum and 5% soil. The non-supplemented standard inoculum was also tested. Tote coupons were steeped in the mixture and incubated at 20°C at 94%, 75%, 54% or 33% relative humidity (RH). Coupons were analyzed and quantified by colony forming units at five time points over 28 days.
Results: Analysis of variance indicated the addition of 5% soil to the mixture of bacteria significantly increased long term bacterial survival over the non-supplemented mixture (P < 0.001); survival was up to 4-5 log higher at all humidity levels, with the exception of 33% RH, where a 3-log increase in survival was observed. Survival at 33% RH was greater than at the higher humidity levels for all the inoculation variations tested (P < 0.001). No significant differences in bacterial survival were detected until 14 days post inoculation. Confocal microscopy confirmed that Salmonellacells were associated with soil components within the mixtures.
Significance: Results indicate improved and regular sanitation of plastic totes must be implemented to reduce the possibility of Salmonella contamination of harvested tomatoes. Adequate washing and removal of soil and other organic material may help reduce Salmonella survival.