Postharvest Handling Conditions Affect Internalization of Salmonella in Baby Spinach during Washing

Gómez‐López, Vicente M.; Marín, Alicia; Allende, Ana; Beuchat, Larry R.; Gil, María I.

doi:10.4315/0362-028x.jfp-12-539

Cited by 19 publications

(14 citation statements)

References 32 publications

(35 reference statements)

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“…In the field, 42 contaminated water, dust containing manures, wildlife animals, and insects can potentially serve 43 as the sources of produce contamination (Berger et al, 2010;Brandl, 2006;Cooley et al, 2014;44 Strawn et al, 2013). At the postharvest level, produce contamination may result from water used for washing and processing produce, workers, or cross-contamination from other food (Beuchat and Ryu, 1997;Gomez-Lopez et al, 2013;Lynch et al, 2009). Additionally, inadequate storage temperature (Alegre et al, 2010;Sim et al, 2013) or minimally processed vegetables such as precut vegetables may facilitate amplification of pathogens on produce (Brandl, 2008).…”

Section: Introductionmentioning

confidence: 99%

Curli fimbriae are conditionally required in Escherichia coli O157:H7 for initial attachment and biofilm formation

et al. 2016

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Several species of enteric pathogens produce curli fimbriae, which may affect their interaction with surfaces and other microbes in nonhost environments. Here we used two Escherichia coli O157:H7 outbreak strains with distinct genotypes to understand the role of curli in surface attachment and biofilm formation in several systems relevant to fresh produce production and processing. Curli significantly enhanced the initial attachment of E. coli O157:H7 to spinach leaves and stainless steel surfaces by 5-fold. Curli was also required for E. coli O157:H7 biofilm formation on stainless steel and enhanced biofilm production on glass by 19-27 fold in LB no-salt broth. However, this contribution was not observed when cells were grown in sterile spinach lysates. Furthermore, both strains of E. coli O157:H7 produced minimal biofilms on polypropylene in LB no-salt broth but considerable amounts in spinach lysates. Under the latter conditions, curli appeared to slightly increase biofilm production. Importantly, curli played an essential role in the formation of mixed biofilm by E. coli O157:H7 and plant-associated microorganisms in spinach leaf washes, as revealed by confocal microscopy. Little or no E. coli O157:H7 biofilms were detected at 4 °C, supporting the importance of temperature control in postharvest and produce processing environments.

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Section: Introductionmentioning

confidence: 99%

Curli fimbriae are conditionally required in Escherichia coli O157:H7 for initial attachment and biofilm formation

et al. 2016

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“…Research has speculated that the low bacteria recovery from food matrixes may be attributed to the strong binding affinity between the bacterial cells and the produce and the internalization of bacteria into plant tissue (16,18,25). Therefore, there is increased need to develop an effective separation strategy so that the levels of bacterial contamination are not underestimated.…”

Section: Introductionmentioning

confidence: 99%

Enzymatic Digestion for Improved Bacteria Separation from Leafy Green Vegetables

Wang

et al. 2016

Journal of Food Protection

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An effective and rapid method for the separation of bacteria from food matrix remains a bottleneck for rapid bacteria detection for food safety. Bacteria can strongly attach to a food surface or internalize within the matrix, making their isolation extremely difficult. Traditional methods of separating bacteria from food routinely involve stomaching, blending, and shaking. However, these methods may not be efficient at removing all the bacteria from complex matrices. Here, we investigate the benefits of using enzyme digestion followed by immunomagnetic separation to isolate Salmonella from spinach and lettuce. Enzymatic digestion using pectinase and cellulase was able to break down the structure of the leafy green vegetables, resulting in the detachment and release of Salmonella from the leaves. Immunomagnetic separation of Salmonella from the liquefied sample allowed an additional separation step to achieve a more pure sample without leaf debris that may benefit additional downstream applications. We have investigated the optimal combination of pectinase and cellulase for the digestion of spinach and lettuce to improve sample detection yields. The concentrations of enzymes used to digest the leaves were confirmed to have no significant effect on the viability of the inoculated Salmonella. Results reported that the recovery of the Salmonella from the produce after enzyme digestion of the leaves was significantly higher (P <0.05) than traditional sample preparation methods to separate bacteria (stomaching and manually shaking). The results demonstrate the potential for use of enzyme digestion prior to separation can improve the efficiency of bacteria separation and increase the likelihood of detecting pathogens in the final detection assay.

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“…Recent studies have demonstrated that exposure of leafy greens to low relative humidity (RH) conditions before washing decreased internalization of Salmonella spp. compared to internalization in baby spinach exposed to high RH (Gomez-Lopez et al, 2013). The effect of cooling on the persistence of human Norovirus GGIi on iceberg lettuce was studied by Mormann et al (2010): neither viral capsid integrity nor genome copy number was significantly reduced by storage at 6ºC for 2 days.…”

Section: Description Of Processing Methods For Leafy Greensmentioning

confidence: 99%

“…These studies illustrate the potential of PAA and NaOCl in reducing the likelihood of cross-contamination during the washing process and establishing a minor reduction of MNV-1, as a surrogate virus for human Norovirus, present on leafy greens. Additionally, if the wash water contains pathogens, they may be internalised in the tissues (Gomez-Lopez et al, 2013). Although many studies have assessed the ability of crops to internalize human bacterial pathogens such as Salmonella through root uptake (Hirneisen et al, 2012), internalisation at the wounded tissue of fresh-cut leafy greens during washing steps in processing has not been extensively studied.…”

Section: Water Sources (Washing)mentioning

confidence: 99%

“…Internalisation of Salmonella in the detached leaves can also occur due to the impact of on farm post-harvest handling conditions. Recently, Gomez-Lopez et al (2013) demonstrated that humidity during on farm postharvest handling affects the internalisation of Salmonella enterica. Exposure of leaves to low relative humidity conditions before washing, which reduced the tissue water content, decreased internalisation of Salmonella compared to high relative humidity.…”

Section: Environmental Factorsmentioning

confidence: 99%

See 1 more Smart Citation

Scientific Opinion on the risk posed by pathogens in food of non‐animal origin. Part 2 (Salmonella and Norovirus in leafy greens eaten raw as salads)

Publication¹

2014

EFS2

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Leafy greens eaten raw as salads are minimally processed and widely consumed foods. Risk factors for leafy greens contamination by Salmonella spp. and Norovirus were considered in the context of the whole food chain including agricultural production and processing. Available estimates of the prevalence of these pathogens (together with the use of Escherichia coli as an indicator organism) in leafy greens were evaluated. Specific mitigation options relating to contamination of leafy greens were considered and qualitatively assessed. It was concluded that each farm environment represents a unique combination of numerous characteristics that can influence occurrence and persistence of pathogens in leafy greens production. Appropriate implementation of food safety management systems, including Good Agricultural Practices (GAP), Good Hygiene Practices (GHP) and Good Manufacturing Practices (GMP), should be primary objectives of leafy green producers. The relevance of microbiological criteria applicable to production, processing and at retail/catering were considered. The current legal framework does not include microbiological criteria applicable at primary production which will validate and verify GAP and GHP. It is proposed to define a criterion at primary production of leafy greens which is designated as Hygiene Criterion, and E. coli was identified as suitable for this purpose. A Process Hygiene Criterion for E. coli in leafy green packaging plants or fresh cutting plants was considered and will also give an indication of the degree to which GAP, GHP, GMP or HACCP programs have been implemented. A Food Safety Criterion for Salmonella in leafy greens could be used as a tool to communicate to producers and processors that Salmonella should not be present in the product. Studies on the prevalence and infectivity of Norovirus are limited, and quantitative data on viral load are scarce making establishment of microbiological criteria for Norovirus on leafy greens difficult.

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Postharvest Handling Conditions Affect Internalization of Salmonella in Baby Spinach during Washing

Cited by 19 publications

References 32 publications

Curli fimbriae are conditionally required in Escherichia coli O157:H7 for initial attachment and biofilm formation

Curli fimbriae are conditionally required in Escherichia coli O157:H7 for initial attachment and biofilm formation

Enzymatic Digestion for Improved Bacteria Separation from Leafy Green Vegetables

Scientific Opinion on the risk posed by pathogens in food of non‐animal origin. Part 2 (Salmonella and Norovirus in leafy greens eaten raw as salads)

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