Fate of Listeria spp. on parsley leaves grown in laboratory and field cultures

• Published in: Journal of applied microbiology Vol. 103; no. 5; pp. 1821 - 1827
• Main Authors: Dreux, N, Albagnac, C, Carlin, F, Morris, C.E, Nguyen-The, C
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.11.2007; Blackwell Publishing Ltd; Blackwell Science; Wiley
• Subjects: Bacteriological Techniques; Biological and medical sciences; Colony Count, Microbial; desiccation; field culture; Food Microbiology; fresh produce; Fundamental and applied biological sciences. Psychology; Humidity; Life Sciences; Listeria; Listeria - growth & development; Listeria innocua; Listeria monocytogenes; Listeria monocytogenes - growth & development; Microbial Viability; Microbiology; Microbiology and Parasitology; parsley; Petroselinum - microbiology; Plant Leaves - microbiology; produce; relative humidity; Santé publique et épidémiologie; Time Factors; Water Microbiology; Relative humidity; Applied microbiology; Desiccation; Petroselinum crispum; fresh produce; field culture; Plant leaf; Laboratory; parsley; Listeria; Fresh product; Dicotyledones; Angiospermae; Bacteria; Spermatophyta; Umbelliferae; Culture; FRESH PRODUCE; RELATIVE HUMIDITY; PARSLEY; HUMIDITE RELATIVE; DESICCATION; FIELD CULTURE; PERSIL
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/j.1365-2672.2007.03419.x

To investigate the population dynamics of Listeria monocytogenes and Listeria innocua on the aerial surfaces of parsley. Under 100% relative humidity (RH) in laboratory and regardless of the inoculum tested (10³-10⁸ CFU per leaf), counts of L. monocytogenes EGDe, LO28, LmP60 and L. innocua CIP 80-12 tended towards approx. 10⁵ CFU per leaf. Under low RH, Listeria spp. populations declined regardless to the inoculum size (10⁴-10⁸ 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 log₁₀ in 2 days in field conditions compared to a decrease of 4·5 log₁₀ 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. 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 log₁₀ scales within 2 days. 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.