. 2021 Jun 20;10(6):1427. doi: 10.3390/foods10061427

Table 2.

Summary of Listeria spp. and L. monocytogenes prevalence throughout the fresh produce supply chain. All Listeria species (including L. monocytogenes) are considered when Listeria spp. are the only target organisms within a study. However, Listeria spp. exclude L. monocytogenes when both are included in target organisms within a study. Prevalence is given in number of positive samples divided by the total number of samples with corresponding percentage in parentheses.

Geographical Location(s)	Sampling Site(s)	Study Duration	Type of Sample(s)	Target Organism(s)	Presence (Yes/Not Detected)	Prevalence	Positive Sample Type(s)	Strain/Serotype	Reference
Natural Environment and Outdoor Production
Colorado	Wilderness areas (n = 5)	Two years	Soil, water, sediment, surface soil, and wildlife feces (n = 572)	Listeria spp. (excludes Lm)	Yes	19/572 (3.32)	All sample types	L. welshimeri and undetermined strains	[27]
Colorado	Wilderness areas (n = 5)	Two years		Listeria monocytogenes	Yes	3/572 (0.52)	Feces and water	1/2a, 1/2b, 3a, 3b, or 7	[27]
Washington, Oregon, and California	Compost facilities (n = 94)	Three weeks	Market-ready, organic compost (n = 94)	Listeria spp. (all)	Yes	22/47 (46.81)	Compost from OR and CA	Not identified	[28]
Arizona, California, Georgia, Kentucky, Maryland, New York, North Carolina, South Carolina, Tennessee	Farms, outside locations, commercial operations	Four years	Organic fertilizers (n = 103)	Listeria monocytogenes	ND	N/A	N/A	N/A	[29]
New York	Natural environments (n = 5)	Two years	Composite soil, drag swab, water, and wildlife/domestic animal feces (n = 1322)	Listeria spp. (excludes Lm)	Yes	186/734 (25.34)	All sample types	L. innocua, L. seeligeri, L. welshimeri, and L. marthii	[25]
New York	Natural environments (n = 5)	Two years		Listeria monocytogenes	Yes	59/734 (8.04)	Not specified	Not identified	[25]
California	Watershed areas near produce field (n = 30)	Two years	Surface water (n = 1405)	Listeria monocytogenes	Yes	~ 604/1405 (43)	Surface water	1/2a, 1/2b, 3a, 4d, and 4e	[30]
California	Watershed areas near produce field (n = 14)	Ten months	Surface water	Listeria monocytogenes	Yes	Culture positive: 22/36 (61.1) PCR positive: 21/36 (58.3)	Surface water	Not identified	[31]
California	Watershed areas near produce field (n = 30)	Three months	Surface water (n = 206)	Listeria monocytogenes	Yes	62/206 (30.1)	Surface water	1/2a, 1/2b, and 4b	[32]
California	Watershed areas (n > 30)	Two years	Surface water (n = 860)	Listeria monocytogenes	Yes	381/860 (44.3)	Surface water	Not identified	[33]
Ohio	Experimental treatments (n = 5) with varying amendments (sawdust, straw, and water) to manure	Sampling occurred over 57-day period	Compost testing occurred on days 0, 14, 28, and 56	Listeria spp. (all)	Yes	Not specified	Day 0: Five compost treatments. Day 3: Three compost treatments. Day 14: One compost treatment	Not identified	[34]
Pennsylvania	Six parallel plots (5 m × 2 m)	Not specified	Irrigation water and spinach	Listeria spp. (all)	ND	N/A	N/A	N/A	[35]
Maine	Randomized complete block split plot design with five replications completed in duplicate	Two years	Liquid dairy, pig, chicken, cow manure, and potatoes grown with and without liquid dairy manure	Listeria monocytogenes	Yes	Total: 3/24 (12.5) Liquid dairy: 2/6 (33.3) Cow: 1/6 (16.7)	Liquid dairy and cow manure	N/A	[36]
Maryland	Mixed produce and dairy farm; 12 sampling sites	14 months	Cow feces, cow feed, cow drinking water, bird feces, bird gathering areas, raw liquid manure, water from lagoon, raw separated solids, partially composted material, fully composed material, surface water, and soil from vegetable production area and cow pasture (n = 159)	Listeria spp. (excludes Lm)	Yes	8/159 (5.03)	Cow feed, cow feces, raw separated solid, windrow compost, finished compost, bird feces, pasture soil	Not identified	[37]
Maryland	Mixed produce and dairy farm; 12 sampling sites	14 months		Listeria monocytogenes	Yes	2/159 (1.26)	Cow feed and pasture soil	Not identified	[37]
Rio Grande Valley and Texas	Cabbage farms with packing sheds and separate packing sheds (n = 6)	Seven months	Cabbage (n = 425), water (n = 205), and environmental (n = 225)	Listeria spp. (excludes Lm)	Yes	24/855 (2.81)	All sample types	L. grayi, L. innocua, L. ivanoii, and L. welshimeri	[38]
Rio Grande Valley and Texas		Seven months		Listeria monocytogenes	Yes	26/855 (3.04)	All sample types	Not identified	[38]
Maryland	Non-tidal freshwater creek	One year	Creek water, soil, radishes, and kale	Listeria monocytogenes	Yes	0.04 and 0.07 MPN/L	Creek water	Not identified	[39]
New York	Spinach fields (n = 2)	Seven weeks	Feces, leaves, soil, and surface water (n = 1492)	Listeria spp. (excludes Lm)	Yes	74/1492 (4.96)	All sample types	Not identified	[40]
New York	Spinach fields (n = 2)	Seven weeks	Feces, leaves, soil, and surface water (n = 1492)	Listeria monocytogenes	Yes	130/1492 (8.71)	All sample types	Not identified	[40]
New York	Natural (n = 4) and urban (n = 4) sites	Two years	Soil, vegetation, surface water, floors, sidewalks, and human contact surfaces (n = 1805)	Listeria monocytogenes	Yes	Urban: 67/898 (7.5) Natural: 13/907 (1.4)	Urban: soil, vegetation, water, sidewalk/floor, and human contact surfaces Natural: soil, vegetation, and water	Not identified	[41]
New York	Natural (n = 4) and urban (n = 4) sites	Two years	Soil, vegetation, surface water, floors, sidewalks, and human contact surfaces (n = 1805)	Listeria spp. (excludes Lm)	Yes	362/1805 (20.1)	Variety from natural and urban sites	L. marthii, L. innocua, L. seeligeri, and L. welshimeri	[42]
New York	Natural (n = 4) and urban (n = 4) sites	Two years		Listeria monocytogenes	Yes	80/1805 (4.43)	Variety from natural and urban sites	Not identified	[42]
Arizona and New York	Watershed areas (n = 9)	Eleven months	Surface water (n = 1053)	Listeria spp. (excludes Lm)	Yes	AZ: 0/76 (0) NY: 58/257 (22.57)	Streams in NY	L. booriae, L. innocua, L. marthii, L. seeligeri, and L. welshimeri	[43]
Arizona and New York	Watershed areas (n = 9)	Eleven months	Surface water (n = 1053)	Listeria monocytogenes	Yes	AZ: 3/76 (3.95) NY: 30/257 (11.67)	Canals in AZ and streams in NY	Not identified	[43]
Arizona	Five sites in two wastewater treatment plants	20 months	Reclaimed and return flow water (n = 28)	Listeria monocytogenes	ND	N/A	N/A	N/A	[44]
Mid-Atlantic U.S.	Convention water sources (n = 6)	Three years	Tidal freshwater river (n = 34), non-tidal freshwater creek (n = 32), reclaimed water holding pond (n = 25), pond water sites (n = 69), and produce wash water (n = 10)	Listeria monocytogenes	Yes	53/170 (31.18)	All sample types	Not identified	[45]
Washington	Red raspberry field with individual plots (22.86 m × 3.05 m; n = 4) with buffer rows between treatment plots; completed in duplicate	Two years	Fertilizer, soil, foliar, and raspberry fruit	Listeria monocytogenes	ND	N/A	N/A	N/A	[46]
New York	Produce farms (n = 5)	27 months	Soil, water (engineered and surface), feces, and drag swabs (n = 588)	Listeria monocytogenes	Yes	88/588 (15.0)	All sample types except for engineered water	Not identified	[47]
New York	Produce farms (n = 21)	Five weeks	Fields (n = 263) and environmental samples (soil, drag swab, and water; n = 600)	Listeria monocytogenes	Yes	Field: 46/263 (17.5) Soil: 30/263 (11) Drag: 21/263 (8) Water: 22/74 (30)	All sample types	Nine allelic types representing lineages I, II, and IIIa	[48]
New York	Produce farms (n = 10)	Six weeks	Terrestrial, water, and fecal (n = 124)	Listeria spp. (excludes Lm)	Yes	24/124 (19.35)	All sample types	L. seeligeri, L. welshimeri, and L. innocua	[49]
New York	Produce farms (n = 10)	Six weeks	Terrestrial, water, and fecal (n = 124)	Listeria monocytogenes	Yes	28/124 (22.58)	All sample types	Not identified	[49]
Packinghouse, Indoor Production, and Processing
Pennsylvania	Small scale mushroom production facility (n = 1)	Two months	NFCS, such as shovels, drains, doors, floors, conveyor belts, brooms, dust pans, etc. (n = 184)	Listeria spp. (excludes Lm)	Yes	26/184 (14.13)	Phase I composting, phase II composting, tray filling line, and growing rooms	L. innocua, L. welshimeri, and L. grayi	[50]
Pennsylvania	Small scale mushroom production facility (n = 1)	Two months		Listeria monocytogenes	Yes	3/184 (1.63)	Phase I composting	Not identified	[50]
Maryland	Organic farms (n = 7)	Two years	Produce (tomatoes, leafy greens, peppers, cucumbers, etc.), well water, and surface water (n = 206)	Listeria monocytogenes	ND	N/A	N/A	N/A	[51]
Southern U.S.	Farms (n = 13) and packing sheds (n = 5)	19 months	Produce (leafy greens, herbs, and cantaloupe; n = 398)	Listeria monocytogenes	ND	N/A	N/A	N/A	[52]
Northeast U.S.	Apple and other tree fruit packinghouses (n = 3)	Six months	NFCS (n = 117)	Listeria monocytogenes	Yes	66/117 (56.41)	Washing, drying, and waxing areas of all facilities	Not identified	[53]
Southern U.S.	Packinghouses (n = 8)	14 months	Leafy greens (n = 109), herbs (n = 165), and cantaloupe (n = 36)	Listeria monocytogenes	Yes	Leafy greens: 3/43 (6.98)	Cabbage	Not identified	[54]
Southeastern U.S.	Packinghouses (n = 11)	Nine months	NFCS, such as forklift wheels, drains, dump tank legs, cold room floors, etc.	Listeria spp. (excludes Lm)	Yes	52/1588 (3.27)	Drains, cold storage rooms, wet NFCS, mobile NFCS, dry NFCS, and outside packing/handling area	L. innouca, L. marthii, L. seeligeri, and L. welshimeri	[55]
Southeastern U.S.	Packinghouses (n = 11)	Nine months		Listeria monocytogenes	Yes	60/1588 (3.78)		Not identified	[55]
California	Stone fruits (n = 105; from seven lots)	Not specified	White nectarines (n = 30), yellow nectarines (n = 30), white peaches (n = 30), and yellow peaches (n = 15)	Listeria monocytogenes	Yes; 11.3 CFU/fruit (geometric mean)	Total: 56/105 (53.3) Nectarines: 15/60 (25) Peaches: 41/45 (91.1)	All sample types	IVb-v1 and 1/2b	[17]
Four U.S. states	Packinghouses (n = 3) and fresh-cut facilities (n = 5)	One year	Sponge samples (n = 2014)	Listeria spp. (excludes Lm)	Yes	Packinghouse: 5/252 (2) to 8/171 (4.7) Fresh-cut: 0/249 (0) to 5/325 (1.5)	Zones 2 and 3 for packinghouse and only zone 3 for fresh-cut	Not identified	[56]
Four U.S. states	Packinghouses (n = 3) and fresh-cut facilities (n = 5)	One year	Sponge samples (n = 2014)	Listeria monocytogenes	Yes	Packinghouse: 2/252 (0.8) to 10/171 (5.8) Fresh-cut: 0/249 (0) to 4/246 (1.6)	Zones 2 and 3 for packinghouse and only zone 3 for fresh-cut	Not identified	[56]
Multiregional	Processing plants (n = 2)	14 months	Baby spinach (n = 409)	Listeria spp. (excludes Lm)	Yes	2/409 (0.49)	Processed samples	L. seeligeri	[57]
Multiregional	Processing plants (n = 2)	14 months	Baby spinach (n = 409)	Listeria monocytogenes	Yes	3/409 (0.73)	One processed and two minimally processed baby spinach samples	Not identified	[57]
Pacific Northwest U.S.	Produce handling and processing facilities (n = 7)	One year	Environmental sponge samples (n = 350)	Listeria spp. (excludes Lm)	Yes	11/350 (3.14)	Drain, entry point, floor, forklift tire, forklift traffic area, equipment leg	L. innocua, L. ivanoii, and L. welshimeri	[58]
Pacific Northwest U.S.	Produce handling and processing facilities (n = 7)	One year	Environmental sponge samples (n = 350)	Listeria monocytogenes	Yes	15/350 (4.29)		1/2a, 3a, 4b, 4d, 4e	[58]
California	Grower (n = 1)	Four months	Conventional and organic spring mix	Listeria monocytogenes	ND	N/A	N/A	N/A	[59]
Not specified	Fresh mushroom slicing and packaging operation; 98 sampling sites within the facility	14 months	NFCS, such as loading dock doors, floors, walls, pallets, drains, squeegees, electrical utility boxes, forklifts, plastic curtains, etc. (n = 255)	Listeria spp. (excludes Lm)	Yes	16/255 (6.27)	Receiving and staging, washing and slicing, packaging, and shipping sites	L. innocua and L. grayi	[60]
Not specified		14 months		Listeria monocytogenes	Yes	48/255 (18.8)	Receiving and staging, washing and slicing, and packaging sites	1/2a, 1/2b, and 1/2c	[60]
Retail
Michigan and New Jersey	Distribution (cilantro), retail (cilantro and mung bean sprouts) and farm (cucumber)	Not specified	Cilantro (pre-retail and retail), cucumbers, and mung bean sprouts	Listeria spp. and Listeria monocytogenes	No live isolates obtained; however, species level proportional abundances illustrate presence of Listeria DNA		L. monocytogenes DNA present in two cilantro samples	Not identified	[61]
South America, North America, Europe, Africa, and Asia	Published studies (n = 25)	Not specified	Packaged salads (n = 20,904), including packaged greens (n = 1212), packaged RTE (n = 11,978), unsure if packaged (n = 2637), and packaged with meat (n = 5077)	Listeria monocytogenes	Yes	543/20,904 (2.60)	All sample types, except for some unsure if packaged samples	Not identified	[62]
Maryland	Retail stores (n = 3)	One year	Basil, cilantro, lettuce, scallion, spinach, and parsley (n = 414)	Listeria monocytogenes	Yes	Not specified	Spinach	Not identified	[63]
California, Texas, Iowa, Minnesota, Ohio, Massachusetts, and Florida	Retail grocery produce departments (n = 30)	Eight months	FCS and NFCS	Listeria monocytogenes	Yes	Total: 226/5112 (4.42) NFCS: 178/2205 (8.1) FCS: 48/2907 (1.7)	Drain (cold room storage), standing water, drain (produce area), squeegee/floor cleaners, floor (cold room storage), etc.	Not identified	[64]
Maryland and California	Retail markets	Over 14 to 23 months	Bagged salads (n = 2966)	Listeria monocytogenes	Yes	Total: 22/2966 (0.74) MD: 8/1465 (0.55) CA: 14/1501 (0.93)	Bagged salads	Not identified	[65]
California, Maryland, Connecticut, and Georgia	Retail stores (n = 1042)	Two years	Produce, including cut vegetables (raw), low-acid cut fruit, and sprouts (n = 6749)	Listeria monocytogenes	Yes	36/6749 (0.53)	All sample types	Not identified	[66]
Virginia	Retail markets	Two months	Whole (n = 20) and sliced (n = 8) shiitake mushrooms	Listeria spp. (excludes Lm)	Yes	Total: 3/28 (10.71) Whole: 1/20 (5) Sliced: 2/8 (25)	Whole and sliced mushrooms	Not identified	[67]
Virginia	Retail markets	Two months	Whole (n = 20) and sliced (n = 8) shiitake mushrooms	Listeria monocytogenes	ND	N/A	N/A	N/A	[67]
Delaware	Grocery stores (number not specified)	15 months	Mushrooms (n = 202) and alfalfa sprouts (n = 206)	Listeria spp. (excludes Lm)	Yes	Total: 24/408 (5.88) Mushroom: 17/202 (8.42) Sprouts: 7/206 (3.40)	Mushroom and sprouts	L. welshimeri, L. innocua, and L. seeligeri	[68]
Delaware	Grocery stores (number not specified)	15 months	Mushrooms (n = 202) and alfalfa sprouts (n = 206)	Listeria monocytogenes	Yes	Total: 1/408 (0.25) Mushroom: 0/202 Sprouts: 1/206 (0.49)	Only sprouts	Not identified	[68]
Seattle, Washington	Retail stores	One year	Sprouts (n = 200) and mushrooms (n = 100)	Listeria monocytogenes	Yes	1/100 (1)	Mushroom	Not identified	[69]
Colorado, Connecticut, Georgia, Maryland, Minnesota, California, Texas, and Washington	Retail locations	Six years	Leafy greens (n = 14,183), sprouts (2652), and melons (3411)	Listeria monocytogenes	Yes	Leafy greens: (0.11) Sprouts: (0.11) Melons: (0.23)	Spinach, romaine, alfalfa sprouts, broccoli sprouts, cucumber, and mango	Not identified	[70]
Philadelphia, Pennsylvania	Retail food establishments (n = 60)	Two years	RTE fresh fruit, greens, and herbs	Listeria monocytogenes	ND	N/A	N/A	N/A	[71]
Minnesota	Supermarket	Not specified	Produce (lettuce, potato peels, corn husks, broccoli stems, cabbage outer leaves, carrot peels, cauliflower stems, mushroom stems, spinach, beet peels, and frozen green beans, pea pods, green peas, and spinach)	Listeria monocytogenes	ND	N/A	N/A	N/A	[72]
Minneapolis, Minnesota	Supermarkets (n = 2)	One year	Produce (broccoli, cabbage, carrots, cauliflower, cucumbers, lettuce, mushrooms, potatoes, radishes, and tomatoes; n = 1000)	Listeria spp. and Listeria monocytogenes	Yes	97/1000 (9.7)	Lettuce, cabbage, cucumbers, mushrooms, potatoes, radishes	L. monocytogenes, L. innocua, L. welshimeri, and L. seeligeri	[73]
Farmers’ Markets
West Virginia and Kentucky	Farmers’ markets (n = 2)	Four months	Produce (tomatoes, peppers, cucumber, cantaloupe, and spinach; n = 212)	Listeria spp. (excludes Lm)	Yes	4/212 (1.89)	Peppers and cantaloupes	Not identified	[74]
West Virginia and Kentucky	Farmers’ markets (n = 2)	Four months		Listeria monocytogenes	Yes	4/212 (1.89)	Tomatoes, cucumbers, and cantaloupes	Not identified	[74]
Pennsylvania	Farmers’ markets (n = 25) and vendors (n = 58)	8 months	Leafy greens (n = 50 each of lettuce, spinach, and kale)	Listeria spp. (excludes Lm)	Yes	5/152 (3.30)	Kale, lettuce, and spinach	Not identified	[75]
Pennsylvania	Farmers’ markets (n = 25) and vendors (n = 58)	8 months	Leafy greens (n = 50 each of lettuce, spinach, and kale)	Listeria monocytogenes	Yes	1/152 (0.66)	Spinach	Not identified	[75]
Washington D.C.	Farmers’ markets and supermarkets	Not specified	Produce (alfalfa sprouts, beets, broccoli, broccoli sprouts, cauliflower, celery, cilantro, cucumbers, field cress, green peppers, lettuce, mung bean sprouts, potatoes, soybean sprouts, watercress, yams; n = 127)	Listeria spp. (excludes Lm)	Yes	19/127 (14.96)	Celery, field cress, lettuce, mung bean sprouts, potatoes, soybean sprouts, watercress, yams	L. innocua, L. welshimeri, and L. grayi	[76]
Washington D.C.	Farmers’ markets and supermarkets	Not specified		Listeria monocytogenes	Yes	6/127 (4.72)	Field cress and potatoes	N/A	[76]
Florida	Farmers’ markets (n = 9) and supermarkets (n = 12)	10 months	Leafy greens (n = 103), berries (n = 106), spinach (n = 77), and tomatoes (n = 115)	Listeria monocytogenes	Yes	4/401 (1)	Leafy greens and spinach from farmer’s markets	Not identified	[77]
Domestic
Philadelphia, Pennsylvania	Homes (n = 100)	One year	Refrigerator door handle, bottom shelf, meat drawer; kitchen counter near sink; used kitchen sponge or dishcloth	Listeria spp. (excludes Lm)	Yes	12/557 (2.15)	Meat drawer	L. innocua, L. welshimeri, L. grayi, and L. seeligeri	[78]
Philadelphia, Pennsylvania	Homes (n = 100)	One year		Listeria monocytogenes	Yes	4/557 (0.72)	Refrigerator door handle, refrigerator drawer, kitchen sink, and dishcloth/sponge	Not identified	[78]