Purpose: To evaluate factors affecting the transfer of E. coli between gloves and lettuce.
Methods: In the laboratory, leaves on Romaine lettuce plants were inoculated with approximately 6 log CFU/leaf of generic E. coli. After 6 or 24 h, pieces (100 cm2) of latex gloves (disposable smooth, or reusable; smooth or textured) were held on the inoculated lettuce surface for 5 s. In Salinas, CA, field, heads of lettuce were inoculated at 7 log CFU/head and dried for 2 h. A single inoculated head of lettuce was harvested with an uninoculated glove before harvesting 20 additional uninoculated heads using the same glove. Latex gloves (disposable smooth or reusable textured) were inoculated with E. coli at 4.5 log CFU/glove, dried for 1 min, and used to harvest 20 heads of lettuce. Lettuce leaves and gloves were homogenized in 0.1% peptone or Dey-Engley broth, respectively, plated on tryptic soy (TS) agar or enriched in TS broth with 50 μg/ml rifampicin and incubated for 24 h at 35°C.
Results: In the laboratory, 10 to 100 cells of E. coli were transferred from inoculated lettuce leaves to gloves, irrespective of drying time or glove type. In the field, after harvesting a single inoculated head of lettuce, sufficient cells were transferred to the glove such that E. coli was detected on 20 subsequent heads of lettuce more than 50% of the time, irrespective of glove type. When gloves were inoculated, E. coli was transferred to a greater proportion of lettuce heads when harvested with disposable gloves than with reusable gloves.
Significance: Contaminated gloves can transfer E. coli to multiple heads of lettuce during harvest; in some cases glove type may impact this transfer.