Document Detail

Plant lesions promote the rapid multiplication of Escherichia coli O157:H7 on postharvest lettuce.
MedLine Citation:
PMID:  18641153     Owner:  NLM     Status:  MEDLINE    
Several outbreaks of Escherichia coli O157:H7 infections have been associated with minimally processed leafy vegetables in the United States. Harvesting and processing cause plant tissue damage. In order to assess the role of plant tissue damage in the contamination of leafy greens with E. coli O157:H7, the effect of mechanical, physiological, and plant disease-induced lesions on the growth of this pathogen on postharvest romaine lettuce was investigated. Within only 4 h after inoculation, the population sizes of E. coli O157:H7 increased 4.0-, 4.5-, and 11.0-fold on lettuce leaves that were mechanically bruised, cut into large pieces, and shredded into multiple pieces, respectively. During the same time, E. coli O157:H7 population sizes increased only twofold on leaves that were left intact after harvest. Also, the population size of E. coli O157:H7 was 27 times greater on young leaves affected by soft rot due to infection by Erwinia chrysanthemi than on healthy middle-aged leaves. Confocal microscopy revealed that leaf tip burn lesions, which are caused by a common physiological disorder of lettuce, harbored dense populations of E. coli O157:H7 cells both internally and externally. Investigation of the colonization of cut lettuce stems by E. coli O157:H7 showed that the pathogen grew 11-fold over 4 h of incubation after its inoculation onto the stems, from which large amounts of latex were released. The results of this study indicate that plant tissue damage of various types can promote significant multiplication of E. coli O157:H7 over a short time and suggest that harvesting and processing are critical control points in the prevention or reduction of E. coli O157:H7 contamination of lettuce.
M T Brandl
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2008-07-18
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  74     ISSN:  1098-5336     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2008 Sep 
Date Detail:
Created Date:  2008-08-29     Completed Date:  2008-09-30     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  5285-9     Citation Subset:  IM    
Produce Safety and Microbiology Research Unit, 800 Buchanan St., Albany, CA 94710, USA.
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MeSH Terms
Colony Count, Microbial
Disease Outbreaks
Escherichia coli Infections / epidemiology
Escherichia coli O157 / growth & development*
Food Handling / methods*
Food Microbiology*
Lettuce / microbiology*
Pectobacterium chrysanthemi / growth & development
Plant Diseases / microbiology
Plant Leaves / microbiology
Plant Stems / microbiology
United States / epidemiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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