Purpose: This work was conducted to determine the survival, injury, and presence of rdar morphotype of Salmonella serovars in soil and water. Additionally, Salmonella biofilm-forming potential on glass and quartz particles was determined.
Methods: Produce outbreak-associated Salmonella serovars were cultured in TSB and washed prior to use. Soil (50 g) obtained from a tomato farm in Virginia was sieved, autoclaved, and then inoculated with 5 ml of Salmonella suspension. Sterile, deionized water (45 ml) was inoculated with 5 ml of Salmonella suspension. Soil and water samples were stored at 30°C for 40 days and sampled every ten days. Bacterial enumeration was performed on XLT-4 and TSA incubated at 35°C for 24-48 hours. Ability to express curli and cellulose (rdar morphotype) was determined using congo red agar. The biofilm forming potential Salmonella serovars was also determined on glass cover slips and quartz particles using 0.1% Crystal Violet staining to estimate biofilm mass.
Results: There was a 2.6 log CFU/g and 2.7 log CFU/ml average decrease in populations of Salmonella serovars in soil and water, respectively, over the 40 day period. Cell injury was greater in soil than in water (P < 0.05). Serovars tested were capable of producing the rdar morphotype on congo red agar. The serovars tested were capable of biofilm attachment to quartz particles and glass.
Significance: Salmonella populations survived well in soil and water and displayed the rdar morphotype that is associated with environmental persistence. Biofilm formation on glass and quartz particles was observed. Extended survival in the farm environment and biofilm formation on soil surfaces may aid in dispersal in the farm environment.