Microbiological Quality of Bagged Cut Spinach and Lettuce Mixes

Division of Microbiology, United States Food and Drug Administration, College Park, Maryland 20740, USA.
Applied and Environmental Microbiology (Impact Factor: 3.67). 03/2008; 74(4):1240-2. DOI: 10.1128/AEM.02258-07
Source: PubMed


Analysis of 100 bagged lettuce and spinach samples showed mean total bacterial counts of 7.0 log(10) CFU/g and a broad range of < 4 to 8.3 log10 CFU/g. Most probable numbers (MPN) of > or = 11,000/g coliforms were found in 55 samples, and generic Escherichia coli bacteria were detected in 16 samples, but no E. coli count exceeded 10 MPN/g.

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Available from: Peter C H Feng, Oct 06, 2015
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    • "However, no clear phenotype has been found to strongly differentiate those groups, raising questions on the mechanisms that led to their formation and more generally on the nature of the differences in bacterial population structures. Low levels of non-pathogenic E. coli are often associated with vegetables after anthropic or natural contaminations , suggesting that interactions between E. coli and agricultural plants are not uncommon (Ibenyassine et al., 2007; Rai and Tripathi, 2007; Ilic et al., 2008; Valentin-Bon et al., 2008; Mandrell, 2009; Caponigro et al., 2010; Oliveira et al., 2010). In the light of past outbreaks linked with the ingestion of vegetables contaminated with enteric pathogens such as Salmonella enterica, E. coli O157:H7, or more recently E. coli O104:H4 (Rohde et al., 2011), it has been suggested that plants could be common vectors and even additional secondary "
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    ABSTRACT: Plants are increasingly considered as secondary reservoirs for commensal and pathogenic Escherichia coli strains, but the ecological and functional factors involved in this association are not clear. To address this question, we undertook a comparative approach combining phenotypic and phylogenetic analyses of E. coli isolates from crops and mammalian hosts. Phenotypic profiling revealed significant differences according to the source of isolation. Notably, isolates from plants displayed higher biofilm and extracellular matrix production and higher frequency of utilization of sucrose and the aromatic compound p-hydroxyphenylacetic acid. However, when compared with mammalian-associated strains, they reached lower growth yields on many C-sources commonly used by E. coli. Strikingly, we observed a strong association between phenotypes and E. coli phylogenetic groups. Strains belonging to phylogroup B1 were more likely to harbour traits indicative of a higher ability to colonize plants, whereas phylogroup A and B2 isolates displayed phenotypes linked to an animal-associated lifestyle. This work provides clear indications that E. coli phylogroups are specifically affected by niche-specific selective pressures, and provides an explanation on why E. coli population structures vary in natural environments, implying that different lineages in E. coli have substantially different transmission ecology.
    Environmental Microbiology 07/2012; 15(2). DOI:10.1111/j.1462-2920.2012.02852.x · 6.20 Impact Factor
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    • "The microbial quality indicators of bagged ready-to-eat salads, fresh vegetables and fruits depends on by several bacteria species (mesophilic aerobic, total and faecal coliforms, Escherichia coli O:157, Salmonella sp., Listeria monocytogenes and Leuconostoc sp.) that affect on shelf-life, quality and safety of these commodities. For this reason, these microorganisms have been widely studied and reported in the previous researches [1] [2] [3] [4] [5] [6] [7] [8] [9]. "
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    ABSTRACT: The aim of this work was to investigate the fungal population dynamics in ready-to-eat bagged samples of rocket (Diplotaxis spp.), lettuce baby leaf (Lactuca sativa L.) and "songino" (Valerianella olitoria L.) during a shelf-life, in order to evaluate the effects of the storage length and season of production on the spoilage processes. The incidence of toxigenic moulds was particularity studied in order to evaluate a potential production of mycotoxins and allergenic conidia. A total of 900 samples collected from 10 Italian trademarks were analyzed at the 2nd, 5th and 8th day after the packaging in the spring and summer. A very high number of fungi was found and a great variability of moulds and yeasts at the 1st day of sampling was observed. Regarding to season of production, any seasonal effect on the moulds and yeasts has been observed, but the moulds detected belonged to different species in relation to season. Regarding to storage length, the yeasts and moulds did not showed significant variations during a shelf-life. In relation to vegetable species, the lettuce resulted always less contaminated with respect to other salads, and the rocket presented 1-2 Log cfu/g of increasing in the level of moulds. Regarding to fungi species, the yeasts were significantly predominant respect to moulds. Finally, the toxigenic moulds Aspergillus flavus and Penicillium italicum were found in all the types of salad in the summer, and their growth during the storage at low temperature represented a potential hazard for the mycotoxins and allergenic conidia production in these commodities.
    Journal of Agricultural Science and Technology 04/2012; 2(4):569-576. · 0.70 Impact Factor
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