Fate of Listeria spp. on parsley leaves grown in laboratory and field cultures.
OBJECTIVE
To investigate the population dynamics of Listeria monocytogenes and Listeria innocua on the aerial surfaces of parsley.


RESULTS
Under 100% relative humidity (RH) in laboratory and regardless of the inoculum tested (10(3)-10(8) CFU per leaf), counts of L. monocytogenes EGDe, LO28, LmP60 and L. innocua CIP 80-12 tended towards approx. 10(5) CFU per leaf. Under low RH, Listeria spp. populations declined regardless to the inoculum size (10(4)-10(8) CFU per leaf). L. innocua CIP 80-12 survived slightly better than L. monocytogenes in the laboratory and was used in field cultures. Under field cultures, counts of L. innocua decreased more rapidly than in the laboratory, representing a decrease of 9 log(10) in 2 days in field conditions compared to a decrease of 4.5 log(10) in 8 days in the laboratory. Counts of L. innocua on tunnel parsley cultures were always higher (at least by 100 times) than those on unprotected parsley culture.


CONCLUSIONS
Even with a high inoculum and under protected conditions (i.e. plastic tunnels), population of L. monocytogenes on the surface of parsley on the field would decrease by several log(10) scales within 2 days.


CONCLUSIONS
Direct contamination of aerial surfaces of parsley with L. monocytogenes (i.e. through contaminated irrigation water) will not lead to contaminated produce unless it occurs very shortly before harvest.
Dreux
N
N
UMR408 Sécurité et Qualité des Produits d'Origine Végétale, INRA, Université d'Avignon, F-84000 Avignon, France. ndreux@avignon.inra.fr
Albagnac
C
C
Carlin
F
F
Morris
C E
CE
Nguyen-The
C
C
D001431:Bacteriological Techniques; D015169:Colony Count, Microbial; D005516:Food Microbiology; D006813:Humidity; D008087:Listeria / Q000254:growth & development*; D008089:Listeria monocytogenes / Q000254:growth & development; D050296:Microbial Viability; D028528:Petroselinum / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology*; D013997:Time Factors; D014871:Water Microbiology