Interactions of Salmonella enterica with lettuce leaves.
OBJECTIVE
To investigate the interactions of Salmonella enterica with abiotic and plant surfaces and their effect on the tolerance of the pathogen to various stressors.


RESULTS
Salmonella strains were tested for their ability to form biofilm in various growth media using a polystyrene plate model. Strong biofilm producers were found to attach better to intact Romaine lettuce leaf tissue compared to weak producers. Confocal microscopy and viable count studies revealed preferential attachment of Salmonella to cut-regions of the leaf after 2 h at 25 degrees C, but not for 18 h at 4 degrees C. Storage of intact lettuce pieces contaminated with Salmonella for 9 days at 4 degrees C resulted only in small changes in population size. Exposure of lettuce-associated Salmonella cells to acidic conditions (pH 3.0) revealed increased tolerance of the attached vs planktonic bacteria.


CONCLUSIONS
Biofilm formation on polystyrene may provide a suitable model to predict the initial interaction of Salmonella with cut Romaine lettuce leaves. Association of the pathogen with lettuce leaves facilitates its persistence during storage and enhances its acid tolerance.


CONCLUSIONS
Understanding the interactions between foodborne pathogens and lettuce might be useful in developing new approaches to prevent fresh produce-associated outbreaks.
Kroupitski
Y
Y
Microbial Food-Safety Research Unit, Department of Food Science, Institute for Technology and Storage of Fresh Produce, Agricultural Research Organization, The Volcani Center, Beth-Dagan, Israel.
Pinto
R
R
Brandl
M T
MT
Belausov
E
E
Sela
S
S
D018441:Biofilms / Q000254:growth & development; D015169:Colony Count, Microbial; D003470:Culture Media; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D018545:Lactuca / Q000382:microbiology*; D008954:Models, Biological; D018515:Plant Leaves / Q000382:microbiology*; D011137:Polystyrenes; D019779:Salmonella enterica / Q000254:growth & development* / Q000502:physiology; D013696:Temperature
D003470:Culture Media; D011137:Polystyrenes