Influence of bovine manure as fertilizer on the bacteriological quality of organic Iceberg lettuce

Abstract

Aim: 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. Methods and 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. Significance and Impact of the Study: 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.

Potential Uptake of Escherichia coli O157:H7 from Organic Manure into Crisphead Lettuce

“…These results concur with those of a field study in which manure naturally contaminated with E. coli O157:H7 was used as a fertilizer on lettuce, and E. coli O157:H7 was not isolated from the lettuce (16). In contrast, other studies that have investigated the risks of using manure as fertilizer on vegetables have found that transmission may occur under experimental conditions both in greenhouses and in the field (11-14, 23, 29).…”

“…Samples of soil, manure, and fertilized soil were each mixed manually before appropriate subsamples were weighed into stomacher bags for further processing. The samples from lettuce (heads and outer leaves) were cut into pieces and prepared as described by Johannessen et al (16). For the underdeveloped lettuce and roots, all the material was cut into pieces and used for analysis.…”

“…The few investigations on the bacteriological quality of organic fruit and vegetables that have been published have found no evidence that these products are of poorer hygienic quality, or have higher numbers of pathogenic bacteria present, than conventionally produced ones (16,(20)(21)(22)27).…”

Microbiological Quality of Organic and Conventional Leafy Vegetables

“…In some scientific studies greater risk with the consumption of organic food was not identified [8,13] but controversially, several foodborne disease outbreaks are related to organic food [14]. One example is the outbreak of Shiga toxin-producing Escherichia coli O157:H7 linked with organic 2 Journal of Food Quality Sprinkler irrigation is a method similar to natural rainfall; water is delivered through a pressurized pipe network to sprinklers which spray the water into the air * Source: Solomon et al [23].…”

Farm Management, Environment, and Weather Factors Jointly Affect the Probability of Spinach Contamination by Generic Escherichia coli at the Preharvest Stage

“…While produce contamination with enteric food-borne pathogens is of high public health and economic concern, the contam-ination events are relatively rare (6,12,13), thus requiring intensive but also expensive sampling and testing efforts. A common practice has been to use generic Escherichia coli as an indicator of fecal contamination of produce (5,6,(13)(14)(15).…”