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Rapid attachment of Listeria monocytogenes to hydroponic and soil grown lettuce leaves

Kyere, Emmanuel O., Foong, Grace, Palmer, Jon, Wargent, Jason J., Fletcher, Graham C., Flint, Steve
Food control 2019 v.101 pp. 77-80
Listeria monocytogenes, exposure duration, fresh produce, hydroponics, lettuce, pathogens, soil
Listeria monocytogenes has been implicated in many foodborne outbreaks involving fresh produce such as lettuce. In order to contaminate the lettuce, the pathogen must attach to the fresh produce. In this study, the attachment of L. monocytogenes strains O8A06, O8A07 and O8A08 to hydroponically grown lettuce as well as lettuce grown with a soil potting mix was evaluated under different exposure times (1 s, 10 s, 30 s, 60 s, 2 min and 5 min). Attachment of L. monocytogenes O8A08 to hydroponically grown lettuce leaves during 2 and 5 min exposure times was significantly higher (p < 0.05) than O8A06 and O8A07. There was no significant difference (p > 0.05) in Listeria attachment to both hydroponic and soil grown lettuce leaves as well as the number attaching to lettuce between the different exposures times tested. The number of L. monocytogenes which attached to both soil and hydroponically grown lettuce leaves within these short exposure times for all the three strains ranged from 0.77 to 1.46 log CFU/cm2. The results indicate that any exposure of lettuce leaves to a source of L. monocytogenes may result in rapid colonisation of the product and therefore, prevention of fresh produce contamination by L. monocytogenes is more important than depending on other control systems to remove contamination.