Abstract
Recently, most foodborne illness outbreaks of salmonellosis have been caused by consumption of contaminated fresh produce. Yet, the mechanisms that allow the human pathogen Salmonella enterica to contaminate and grow in plant environments remain poorly described. We examined the effect of feeding by phytophagous insects on survival of S. enterica on lettuce. Larger S. enterica populations were found on leaves infested with Macrosteles quadrilineatus. In contrast, pathogen populations among plants exposed to Frankliniella occidentalis or Myzus persicae were similar to those without insects. However, on plants infested with F. occidentalis, areas of the infested leaf with feeding damage sustained higher S. enterica populations than areas without damage. The spatial distribution of S. enterica cells on leaves infested with F. occidentalis may be altered resulting in higher populations in feeding lesions or survival may be different across a leaf dependent on local damage. Results suggest the possibility of some specificity with select insects and the persistence of S. enterica. Additionally, we demonstrated the potential for phytophagous insects to become contaminated with S. enterica from contaminated plant material. S. enterica was detected in approximately 50% of all M. quadrilineatus, F. occidentalis, and M. persicae after 24 h exposure to contaminated leaves. Particularly, 17% of F. occidentalis, the smallest of the insects tested, harbored more than 102 CFU/F. occidentalis. Our results show that phytophagous insects may influence the population dynamics of S. enterica in agricultural crops. This study provides evidence of a human bacterial pathogen interacting with phytophagous insect during plant infestation.
Highlights
The frequency and severity of produce-related foodborne illness outbreaks have increased in the last few decades [1,2]
Lettuce plants inoculated with S. enterica were exposed to F. occidentalis to investigate if insect infestation influenced S. enterica populations
S. enterica was not recovered from uninoculated control plants
Summary
The frequency and severity of produce-related foodborne illness outbreaks have increased in the last few decades [1,2]. In the US, Salmonella enterica is the number one cause of bacterial foodborne illness, and the incidence of infection has not declined over the past 15 years, and instead, has increased slightly since mid-2000s [3,4]. Net growth of S. enterica on leaves is rare and populations tend to decline steadily overtime [6,7,8]. This suggests that multiplication factors are required to induce growth of bacterial populations or sustain infectious populations for extended periods, in what is normally described as a nonhost environment. The role of additional biological multipliers, such as phytophagous insects remains unexplored
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