Salmonella has a sweet tooth for lettuce

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Salmonella has a sweet tooth for lettuce
A possible route by which Salmonella could infect commercially available lettuce is clarified in
a report online this week in The ISME Journal. The study reveals that Salmonella actively
moves towards a sugar-like carbon source found in the root extracts of lettuce, and that in the
presence of these root extracts the bacteria activate genes that enable them to attach to the
lettuce root cells.
Salmonella bacteria are some of the most commonly known bacterial pathogens to
cause human illness, with infection often resulting in food poisoning. Well-established
common causes of infection involve poultry, raw eggs and food that has been cooked or
defrosted and not eaten straight away. However, it is also recognized that human pathogenic
bacteria can be found associated with fresh produce – such as lettuce. In the present study
Michel Klerks and colleagues examine the interactions between Salmonella and commercially
available lettuce. They report that the Salmonella bacteria actively move towards the lettuce
roots, and that this movement is associated with a sugar-like carbon source excreted by the
roots. Genetic analysis revealed that pathogenicity-related genes in Salmonella are induced
in the presence of the roots – demonstrating that Salmonella is conditioned for attachment to
the lettuce roots.
The authors suggest that knowledge of the route of infection of susceptible plants
could be the basis for development of strategies to prevent infection by the Salmonella
bacteria. They stress, however, that the risk of infection of plant produce is still relatively low
compared to that of Salmonellosis associated with poultry or eggs.
Differential interaction of Salmonella enterica serovars with lettuce cultivars and plantmicrobe factors influencing the colonization efficiency
Michel M Klerks, Eelco Franz, Marga van Gent-Pelzer, Carolien Zijlstra and Ariena H C van
Author contacts:
Michel Klerks (Wageningen University, Plant Research International BV, The Netherlands)
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