Influence of bovine manure as fertilizer on the bacteriological quality of organic Iceberg lettuce.
OBJECTIVE
To investigate the bacteriological quality, and the occurrence of selected pathogenic bacteria from organically grown Iceberg lettuce fertilized with bovine manure in the form of compost, firm manure and slurry in a 2-year field trial.


RESULTS
Samples of soil, fertilizer, fertilized soil, seedlings and lettuce were analysed for aerobic plate counts (APC), thermotolerant coliform bacteria (TCB), Escherichia coli, E. coli O157:H7, Salmonella spp. and Listeria monocytogenes. No difference in bacteriological quality could be shown in lettuce at harvest, however, APC varied significantly from year to year in the study. The various treatments gave significantly different APC and numbers of TCB isolated from fertilized soil. Escherichia coli O157:H7 was isolated from firm manure and slurry, and soils fertilized with the respective fertilizers the second year, but were not recovered from the lettuce.


CONCLUSIONS
No difference in bacteriological quality could be detected in lettuce at harvest after application of various types of manure-based fertilizers grown under Norwegian conditions.


CONCLUSIONS
The results may indicate that the use of manure does not have considerable influence on the bacteriological quality of organic lettuce. However, others have suggested that there is a risk by using manure. There is a need for more research in the field.
Johannessen
G S
GS
Section for Food and Feed Microbiology, National Veterinary Institute, Oslo, Norway. gro.johannessen@vetinst.no
Frøseth
R B
RB
Solemdal
L
L
Jarp
J
J
Wasteson
Y
Y
M  Rørvik
L
L
D000818:Animals; D001419:Bacteria / Q000302:isolation & purification*; D002417:Cattle; D019453:Escherichia coli O157 / Q000302:isolation & purification; D005308:Fertilizers; D005506:Food Contamination; D005516:Food Microbiology; D006801:Humans; D018545:Lactuca / Q000254:growth & development / Q000382:microbiology*; D008089:Listeria monocytogenes / Q000302:isolation & purification; D008372:Manure; D009664:Norway; D012475:Salmonella / Q000302:isolation & purification; D012988:Soil Microbiology
D005308:Fertilizers; D008372:Manure