Salmonella as an endophytic colonizer of plants - A risk for health safety vegetable production

Kljujev, Igor; Raičević, Vera; Vujović, Bojana; Rothballer, Michael; Schmid, Michael

doi:10.1016/j.micpath.2017.12.020

Cited by 27 publications

(19 citation statements)

References 41 publications

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“…Typhimurium ATCC14028, and S . Typhimurium S1 into the root of different plants, including lettuce, was demonstrated recently using a sterile system and subsequent FISH-CLSM analysis (Kljujev et al, 2018). In the case of basil, internalization of S. Thompson strain FMFP 899 via roots was demonstrated using Salmonella -soaked germination discs using high cell counts of Salmonella for inoculation (Li and Uyttendaele, 2018).…”

Section: Discussionmentioning

confidence: 99%

Salmonella Establishment in Agricultural Soil and Colonization of Crop Plants Depend on Soil Type and Plant Species

et al. 2019

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Human pathogenic bacteria, such as Salmonella enterica , are able to colonize crop plants. So far, not much is known about biotic and abiotic factors influencing this colonization in field soil. This understanding, however, is imperative for the provision of safe fresh produce to the consumer. In this study, we investigated the effects of soil type, organic fertilization, plant species and the way of Salmonella entry into the plant production system, on the survival of S. enterica in soil as well as the colonization of plants. The selected S. enterica serovar Typhimurium strain 14028s, S. Typhimurium strain LT2 and S. Senftenberg were able to persist in soil for several weeks. Salmonella’s persistence in soil was prolonged in loamy, if compared to sandy soil, and when applied together with organic fertilizer. The leaves of lettuce and corn salad were colonized by S. enterica providing evidence for internalization from the soil via the root. Colonization rates were affected by soil type, plant species and S. enterica strain. Overall, S. enterica was detected in leaves of 0.5–0.9% of the plants, while lettuce was more frequently colonized than corn salad. Plants grown in sandy soil were more often colonized than plants grown in loamy soil. After spray inoculation, S. enterica could be detected on and in leaves for several weeks by cultivation-depending methods, confirmed by confocal microscopy using GFP-labeled S. Typhimurium 14028s. On the one hand, transcriptome data from S. Typhimurium 14028s assessed in response to lettuce medium or lettuce root exudates showed an upregulation of genes associated with biofilm formation and virulence. On the other hand, lettuce inoculated with S. Typhimurium 14028s showed a strong upregulation of genes associated with plant immune response and genes related to stress response. In summary, these results showed that organic fertilizers can increase the persistence of Salmonella in soil and that soil type and plant species play a crucial role in the interactions between human pathogens and crop plants. This understanding is therefore a starting point for new strategies to provide safe food for the consumer.

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Section: Discussionmentioning

confidence: 99%

Salmonella Establishment in Agricultural Soil and Colonization of Crop Plants Depend on Soil Type and Plant Species

et al. 2019

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“…Cross-contamination of fieldgrown vegetables by the foodborne pathogens through the contaminated irrigation water with fecal waste or improperly composted manure is suggested to be a possible source of pathogen at the pre-harvest level (Oliveira et al, 2012). Attachment of human bacterial pathogens on fresh produce during spray irrigation can be affected by the bacterial strains, bacterial population, stress tolerance, and their biofilm formation ability (Carey et al, 2009;Ge et al, 2012;Yaron and Römling, 2014;Kljujev et al, 2018). Other factors such as produce growing conditions, plant development stage, and the leaf characteristics of cultivars also affect bacterial attachment on the fresh produce leaf (Barak et al, 2011;Ge et al, 2012;Hirneisen et al, 2012;Quilliam et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Persistence of Escherichia coli O157:H12 and Escherichia coli K12 as Non-pathogenic Surrogates for O157:H7 on Lettuce Cultivars Irrigated With Secondary-Treated Wastewater and Roof-Collected Rain Water in the Field

Yin

Gupta

Chen

et al. 2020

Front. Sustain. Food Syst.

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Treated wastewater (TW) and roof-collected rain water (RW) that meet the required microbial quality as per Food Safety Modernization Act (FSMA) regulation may serve as alternative irrigation water sources to decrease the pressure on the current water scarcity. Alternative water sources may have different water characteristics that influence the survival and transfer of microorganisms to the irrigated produce. Further, these water sources may contain pathogenic bacteria such as Shiga-toxigenic Escherichia coli. To evaluate the risk associated with TW and RW irrigation on the fresh produce safety, the effect of TW and RW irrigation on the transfer of two non-pathogenic E. coli strains as surrogates for E. coli O157:H7 to different lettuce cultivars grown in the field was investigated. Lettuce cultivars “Annapolis,” “Celinet,” and “Coastline” were grown in the field at the Fulton farm (Chambersburg, PA). Approximately 10 days before harvest, lettuce plants were spray-irrigated with groundwater (GW), TW, or RW containing 6 log CFU ml−1 of a mixture of nalidixic acid-resistant E. coli O157:H12 and chloramphenicol-resistant E. coli K12 in fecal slurry as non-pathogenic surrogates for E. coli O157:H7. On 0, 1, 3, 7, and 10 days post-irrigation, four replicate lettuce leaf samples (30 g per sample) from each group were collected and pummeled in 120 ml of buffered peptone water for 2 min, followed by spiral plating on MacConkey agars with antibiotics. Results showed that the recovery of E. coli O157:H12 was significantly greater than the populations of E. coli K12 recovered from the irrigated lettuce regardless of the water sources and the lettuce cultivars. The TW irrigation resulted in the lowest recovery of the E. coli surrogates on the lettuce compared to the populations of these bacteria recovered from the lettuce with RW and GW irrigation on day 0. The difference in leaf characteristics of lettuce cultivars significantly influenced the recovery of these surrogates on lettuce leaves. Populations of E. coli O157:H12 recovered from the RW-irrigated “Annapolis” lettuce were significantly lower than the recovery of this bacterium from the “Celinet” and “Coastline” lettuce (P < 0.05). Overall, the recovery of specific E. coli surrogates from the RW and TW irrigated lettuce was comparable to the lettuce with the GW irrigation, where GW served as a baseline water source. E. coli O157:H12 could be a more suitable surrogate compared to E. coli K12 because it is an environmental watershed isolate. The findings of this study provide critical information in risk assessment evaluation of RW and TW irrigation on lettuce in Mid-Atlantic area.

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“…It has been recently reported [44] that antibiotics can be taken up by plant roots, and then translocated to the fruit and leaves, where a sub-lethal amount of antibiotics (such as tetracycline, streptomycin, and ciprofloxacin) has been detected. In addition, plant internal colonization by opportunistic human pathogens occurs in different crops [53,54]. In this regard, none of the eight selected strains belonged to species reported to be a human opportunist pathogen and they all showed a low level of resistance to the antibiotics considered in this work.…”

Section: Discussionmentioning

confidence: 88%

Screening of Bacterial Endophytes Able to Promote Plant Growth and Increase Salinity Tolerance

et al. 2020

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Bacterial endophytes can colonize plant tissues without harming the plant. Instead, they are often able to increase plant growth and tolerance to environmental stresses. In this work, new strains of bacterial endophytes were isolated from three economically important crop plants (sorghum, cucumber and tomato) grown in three different regions in soils with different management. All bacterial strains were identified by 16S rRNA sequencing and characterized for plant beneficial traits. Based on physiological activities, we selected eight strains that were further tested for their antibiotic resistance profile and for the ability to efficiently colonize the interior of sorghum plants. According to the results of the re-inoculation test, five strains were used to inoculate sorghum seeds. Then, plant growth promotion activity was assessed on sorghum plants exposed to salinity stress. Only two bacterial endophytes increased plant biomass, but three of them delayed or reduced plant salinity stress symptoms. These five strains were then characterized for the ability to produce the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which is involved in the increase of stress tolerance. Pseudomonas brassicacearum SVB6R1 was the only strain that was able to produce this enzyme, suggesting that ACC deaminase is not the only physiological trait involved in conferring plant tolerance to salt stress in these bacterial strains.

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Salmonella as an endophytic colonizer of plants - A risk for health safety vegetable production

Cited by 27 publications

References 41 publications

Salmonella Establishment in Agricultural Soil and Colonization of Crop Plants Depend on Soil Type and Plant Species

Salmonella Establishment in Agricultural Soil and Colonization of Crop Plants Depend on Soil Type and Plant Species

Persistence of Escherichia coli O157:H12 and Escherichia coli K12 as Non-pathogenic Surrogates for O157:H7 on Lettuce Cultivars Irrigated With Secondary-Treated Wastewater and Roof-Collected Rain Water in the Field

Screening of Bacterial Endophytes Able to Promote Plant Growth and Increase Salinity Tolerance

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