Growth and Survival of Salmonella montevideo on Tomatoes and Disinfection with Chlorinated Water

Abstract

The survival on tomato fruits (Lycopersicum esculentum) of a rifampicin-resistant strain of Salmonella montevideo (Centers for Disease Control and Prevention [CDC] isolate G4639), the alleged source of the 1993 multistate outbreak of salmonellosis, was affected by inoculum dose and inoculation site (unbroken surface or wounds and stem scars), as well as by the medium (distilled water, Butterfield's buffer, or trypticase soy broth [TSB]) used to deliver the bacterium, This bacterium inoculated at 4 log10 CFU (colony forming units) per site in distilled water survived for 20 h on tomato skin. However, comparable survival occurred at the stem scars and growth cracks with smaller inoculum doses (3 log10 CFU). The bacterial populations increased rapidly on puncture wounds and tomato slices but decreased on the unbroken surface and stem scar. With unbroken skin and approximately 4 log10 CFU per site, the population survived for at least 48 h but could not be consistently detected after 5 days. By contrast, the stem scar population survived for at least 7 days and decreased only 1 to 2 log10 units. The inherently low pH of the tomatoes did not inhibit bacterial growth. Treatment with 100 ppm of aqueous chlorine for up to 2 min failed to kill all bacteria at these inoculation sites. This was especially true when the bacterial suspensions were prepared in TSB. TSB supported better bacterial survival and/or growth and also protected against the bactericidal effect of aqueous chlorine.

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

“…Our previous study [24] showed that minimum initial inoculum size for the S. typhimurium growth on the tomato surface was determined to be 3 log CFU/tomato surface with diluted nutrients. These findings agreed with Wei et al 's [31] study (1995) in that S. Montevideo could grow with the help of nutrients (for example, in puncture wounds). Without any nutrient sources, the bacteria could only survive for several days on tomato surfaces at 20 and 25°C.…”

Extending and measuring the quality of fresh-cut fruit and vegetables: a review

“…There is a controversy about the formation of carcinogenic chlorinated compounds in water (chloramines and trihalomethanes), calling into question the use of chlorine (Wei et al, 1999). The current concern associated with chlorine outlines the need for research on other treatments suitable for use on fresh-cut products.…”

Whey permeate as a bio-preservative for shelf life maintenance of fresh-cut vegetables

“…Chlorine solutions have been widely used to sanitise fresh-cut fruits and vegetables in the industry. However, the possible formation of carcinogenic chlorinated compounds in water has called into question the use of chlorine in food processing plants (Dychdala, 1991;Page, Harris, & Epstein, 1976;Wei et al, 1999). Moreover, the antimicrobial effectiveness of cold chlorinated water is limited due to hydrophobic plant surfaces that are believed to limit contact between chlorine solutions and microbial contaminants (Adams, 1991;Beuchat, 1992).…”