Fate of <i>Salmonella enterica</i> Serovar Typhimurium on Carrots and Radishes Grown in Fields Treated with Contaminated Manure Composts or Irrigation Water

TLDR

The study investigates how Salmonella enterica serovar Typhimurium persists in soils amended with three types of manure compost or contaminated irrigation water and on carrots and radishes grown in those soils. A split‑plot block design with five treatments—no compost, poultry manure compost, dairy cattle manure compost, alkaline‑pH stabilized dairy cattle manure compost, and contaminated water—was applied to each crop in five replicates, and Salmonella levels were monitored over time. Salmonella survived 203–231 days in soil, was detected on radishes after 84 days and on carrots after 203 days, with greatest persistence in poultry compost–amended soil and lowest in alkaline‑pH stabilized dairy cattle manure compost, indicating that both contaminated compost and irrigation water can keep the pathogen in soil and root vegetables for several months.

Abstract

ABSTRACT Three different types of compost, PM-5 (poultry manure compost), 338 (dairy cattle manure compost), and NVIRO-4 (alkaline-pH-stabilized dairy cattle manure compost), and irrigation water were inoculated with an avirulent strain of Salmonella enterica serovar Typhimurium at 10 7 CFU g −1 and 10 5 CFU ml −1 , respectively, to determine the persistence of salmonellae in soils containing these composts, in irrigation water, and also on carrots and radishes grown in these contaminated soils. A split-plot block design plan was used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but with contaminated water applied) and five replicates for a total of 25 plots for each crop, with each plot measuring 1.8 × 4.6 m. Salmonellae persisted for an extended period of time, with the bacteria surviving in soil samples for 203 to 231 days, and were detected after seeds were sown for 84 and 203 days on radishes and carrots, respectively. Salmonella survival was greatest in soil amended with poultry compost and least in soil containing alkaline-pH-stabilized dairy cattle manure compost. Survival profiles of Salmonella on vegetables and soil samples contaminated by irrigation water were similar to those observed when contamination occurred through compost. Hence, both contaminated manure compost and irrigation water can play an important role in contaminating soil and root vegetables with salmonellae for several months.