Adaptation of Salmonella enterica Serovar Senftenberg to Linalool and Its Association with Antibiotic Resistance and Environmental Persistence

ABSTRACT A clinical isolate of Salmonella enterica serovar Senftenberg, isolated from an outbreak linked to the herb Ocimum basilicum L. (basil), has been shown to be resistant to basil oil and to the terpene alcohol linalool. To better understand how human pathogens might develop resistance to linalool and to investigate the association of this resistance with resistance to different antimicrobial agents, selective pressure was applied to the wild-type strain by sequential exposure to increasing concentrations of linalool. The results demonstrated that S. Senftenberg adapted to linalool with a MIC increment of at least 8-fold, which also resulted in better resistance to basil oil and better survival on harvested basil leaves. Adaptation to linalool was shown to confer cross protection against the antibiotics trimethoprim, sulfamethoxazole, piperacillin, chloramphenicol, and tetracycline, increasing their MICs by 2- to 32-fold. The improved resistance was shown to correlate with multiple phenotypes that included changes in membrane fatty acid composition, induced efflux, reduced influx, controlled motility, and the ability to form larger aggregates in the presence of linalool. The adaptation to linalool obtained in vitro did not affect survival on the basil phyllosphere in planta and even diminished survival in soil, suggesting that development of extreme resistance to linalool may be accompanied by a loss of fitness. Altogether, this report notes the concern regarding the ability of human pathogens to develop resistance to commercial essential oils, a resistance that is also associated with cross-resistance to antibiotics and may endanger public health. IMPORTANCE Greater consumer awareness and concern regarding synthetic chemical additives have led producers to control microbial spoilage and hazards by the use of natural preservatives, such as plant essential oils with antimicrobial activity. This report establishes, however, that these compounds may provoke the emergence of resistant human pathogens. Herein, we demonstrate the acquisition of resistance to basil oil by Salmonella Senftenberg. Exposure to linalool, a component of basil oil, resulted in adaptation to the basil oil mixture, as well as cross protection against several antibiotics and better survival on harvested basil leaves. Collectively, this work highlights the hazard to public health while using plant essential oils without sufficient knowledge about their influence on pathogens at subinhibitory concentrations.

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Multidrug Resistance Salmonella Genomic Island 1 in a Morganella morganii subsp. morganii Human Clinical Isolate from France

mSphere ◽

10.1128/msphere.00118-17 ◽

2017 ◽

Vol 2 (2) ◽

Cited By ~ 21

Author(s):

Eliette Schultz ◽

Olivier Barraud ◽

Jean-Yves Madec ◽

Marisa Haenni ◽

Axel Cloeckaert ◽

...

Keyword(s):

Public Health ◽

Multidrug Resistance ◽

Resistance Genes ◽

Salmonella Enterica ◽

Genomic Island ◽

Multidrug Resistant ◽

Health Concern ◽

Human Pathogens ◽

Morganella Morganii ◽

Content Type

ABSTRACT Since its initial identification in epidemic multidrug-resistant Salmonella enterica serovar Typhimurium DT104 strains, several SGI1 variants, SGI1 lineages, and SGI1-related elements (SGI2, PGI1, and AGI1) have been described in many bacterial genera (Salmonella, Proteus, Morganella, Vibrio, Shewanella, etc.). They constitute a family of multidrug resistance site-specific integrative elements acquired by horizontal gene transfer, SGI1 being the best-characterized element. The horizontal transfer of SGI1/PGI1 elements into other genera is of public health concern, notably with regard to the spread of critically important resistance genes such as ESBL and carbapenemase genes. The identification of SGI1 in Morganella morganii raises the issue of (i) the potential for SGI1 to emerge in other human pathogens and (ii) its bacterial host range. Further surveillance and research are needed to understand the epidemiology, the spread, and the importance of the members of this SGI1 family of integrative elements in contributing to antibiotic resistance development. Salmonella genomic island 1 (SGI1) is a multidrug resistance integrative mobilizable element that harbors a great diversity of antimicrobial resistance gene clusters described in numerous Salmonella enterica serovars and also in Proteus mirabilis. A serious threat to public health was revealed in the recent description in P. mirabilis of a SGI1-derivative multidrug resistance island named PGI1 (Proteus genomic island 1) carrying extended-spectrum-β-lactamase (ESBL) and metallo-β-lactamase resistance genes, bla VEB-6 and bla NDM-1, respectively. Here, we report the first description of Salmonella genomic island 1 (SGI1) in a multidrug-resistant clinical Morganella morganii subsp. morganii strain isolated from a patient in France in 2013. Complete-genome sequencing of the strain revealed SGI1 variant SGI1-L carrying resistance genes dfrA15, floR, tetA(G), bla PSE-1 (now referred to as bla CARB-2), and sul1, conferring resistance to trimethoprim, phenicols, tetracyclines, amoxicillin, and sulfonamides, respectively. The SGI1-L variant was integrated into the usual chromosome-specific integration site at the 3′ end of the trmE gene. Beyond Salmonella enterica and Proteus mirabilis, the SGI1 integrative mobilizable element may thus also disseminate its multidrug resistance phenotype in another genus belonging to the Proteae tribe of the family Enterobacteriaceae. IMPORTANCE Since its initial identification in epidemic multidrug-resistant Salmonella enterica serovar Typhimurium DT104 strains, several SGI1 variants, SGI1 lineages, and SGI1-related elements (SGI2, PGI1, and AGI1) have been described in many bacterial genera (Salmonella, Proteus, Morganella, Vibrio, Shewanella, etc.). They constitute a family of multidrug resistance site-specific integrative elements acquired by horizontal gene transfer, SGI1 being the best-characterized element. The horizontal transfer of SGI1/PGI1 elements into other genera is of public health concern, notably with regard to the spread of critically important resistance genes such as ESBL and carbapenemase genes. The identification of SGI1 in Morganella morganii raises the issue of (i) the potential for SGI1 to emerge in other human pathogens and (ii) its bacterial host range. Further surveillance and research are needed to understand the epidemiology, the spread, and the importance of the members of this SGI1 family of integrative elements in contributing to antibiotic resistance development.

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Evidence for Inhibition of Topoisomerase 1A by Gold(III) Macrocycles and Chelates TargetingMycobacterium tuberculosisandMycobacterium abscessus

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01696-17 ◽

2018 ◽

Vol 62 (5) ◽

Cited By ~ 6

Author(s):

Rashmi Gupta ◽

Carolina Rodrigues Felix ◽

Matthew P. Akerman ◽

Kate J. Akerman ◽

Cathryn A. Slabber ◽

...

Keyword(s):

Mycobacterium Abscessus ◽

Cross Resistance ◽

Human Pathogens ◽

Intrinsic Resistance ◽

Content Type ◽

Starting Point ◽

Scalable Synthesis ◽

High Level ◽

Novel Drug

ABSTRACTMycobacterium tuberculosisand the fast-growing speciesMycobacterium abscessusare two important human pathogens causing persistent pulmonary infections that are difficult to cure and require long treatment times. The emergence of drug-resistantM. tuberculosisstrains and the high level of intrinsic resistance ofM. abscessuscall for novel drug scaffolds that effectively target both pathogens. In this study, we evaluated the activity of bis(pyrrolide-imine) gold(III) macrocycles and chelates, originally designed as DNA intercalators capable of targeting human topoisomerase types I and II (Topo1 and Topo2), againstM. abscessusandM. tuberculosis. We identified a total of 5 noncytotoxic compounds active against both mycobacterial pathogens under replicatingin vitroconditions. We chose one of these hits, compound 14, for detailed analysis due to its potent bactericidal mode of inhibition and scalable synthesis. The clinical relevance of this compound was demonstrated by its ability to inhibit a panel of diverseM. tuberculosisandM. abscessusclinical isolates. Prompted by previous data suggesting that compound 14 may target topoisomerase/gyrase enzymes, we demonstrated that it lacked cross-resistance with fluoroquinolones, which target theM. tuberculosisgyrase.In vitroenzyme assays confirmed the potent activity of compound 14 against bacterial topoisomerase 1A (Topo1) enzymes but not gyrase. Novel scaffolds like compound 14 with potent, selective bactericidal activity againstM. tuberculosisandM. abscessusthat act on validated but underexploited targets like Topo1 represent a promising starting point for the development of novel therapeutics for infections by pathogenic mycobacteria.

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Antimicrobial Susceptibility to Azithromycin among Salmonella enterica Isolates from the United States

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00590-11 ◽

2011 ◽

Vol 55 (9) ◽

pp. 3985-3989 ◽

Cited By ~ 49

Author(s):

Maria Sjölund-Karlsson ◽

Kevin Joyce ◽

Karen Blickenstaff ◽

Takiyah Ball ◽

Jovita Haro ◽

...

Keyword(s):

United States ◽

Antimicrobial Susceptibility ◽

Salmonella Enterica ◽

Antimicrobial Agents ◽

The United States ◽

Outcome Data ◽

Content Type ◽

Susceptibility Data ◽

Retail Meat ◽

Clinical Breakpoints

ABSTRACTDue to emerging resistance to traditional antimicrobial agents, such as ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol, azithromycin is increasingly used for the treatment of invasiveSalmonellainfections. In the present study, 696 isolates of non-TyphiSalmonellacollected from humans, food animals, and retail meats in the United States were investigated for antimicrobial susceptibility to azithromycin. Seventy-twoSalmonella entericaserotype Typhi isolates from humans were also tested. For each isolate, MICs of azithromycin and 15 other antimicrobial agents were determined by broth microdilution. Among the non-TyphiSalmonellaisolates, azithromycin MICs among human isolates ranged from 1 to 32 μg/ml, whereas the MICs among the animal and retail meat isolates ranged from 2 to 16 μg/ml and 4 to 16 μg/ml, respectively. AmongSalmonellaserotype Typhi isolates, the azithromycin MICs ranged from 4 to 16 μg/ml. The highest MIC observed in the present study was 32 μg/ml, and it was detected in three human isolates belonging to serotypes Kentucky, Montevideo, and Paratyphi A. Based on our findings, we propose an epidemiological cutoff value (ECOFF) for wild-typeSalmonellaof ≤16 μg/ml of azithromycin. The susceptibility data provided could be used in combination with clinical outcome data to determine tentative clinical breakpoints for azithromycin andSalmonella enterica.

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Efficacy of Biocides Used in the Modern Food Industry To Control Salmonella enterica, and Links between Biocide Tolerance and Resistance to Clinically Relevant Antimicrobial Compounds

Applied and Environmental Microbiology ◽

10.1128/aem.07534-11 ◽

2012 ◽

Vol 78 (9) ◽

pp. 3087-3097 ◽

Cited By ~ 106

Author(s):

Orla Condell ◽

Carol Iversen ◽

Shane Cooney ◽

Karen A. Power ◽

Ciara Walsh ◽

...

Keyword(s):

Salmonella Enterica ◽

Food Industry ◽

Multidrug Resistant ◽

Cross Resistance ◽

Antimicrobial Compounds ◽

Cross Tolerance ◽

Content Type ◽

Food Grade ◽

High Level

ABSTRACTBiocides play an essential role in limiting the spread of infectious disease. The food industry is dependent on these agents, and their increasing use is a matter for concern. Specifically, the emergence of bacteria demonstrating increased tolerance to biocides, coupled with the potential for the development of a phenotype of cross-resistance to clinically important antimicrobial compounds, needs to be assessed. In this study, we investigated the tolerance of a collection of susceptible and multidrug-resistant (MDR)Salmonella entericastrains to a panel of seven commercially available food-grade biocide formulations. We explored their abilities to adapt to these formulations and their active biocidal agents, i.e., triclosan, chlorhexidine, hydrogen peroxide, and benzalkonium chloride, after sequential rounds ofin vitroselection. Finally, cross-tolerance of different categories of biocidal formulations, their active agents, and the potential for coselection of resistance to clinically important antibiotics were investigated. Six of seven food-grade biocide formulations were bactericidal at their recommended working concentrations. All showed a reduced activity against both surface-dried and biofilm cultures. A stable phenotype of tolerance to biocide formulations could not be selected. Upon exposure ofSalmonellastrains to an active biocidal compound, a high-level of tolerance was selected for a number ofSalmonellaserotypes. No cross-tolerance to the different biocidal agents or food-grade biocide formulations was observed. Most tolerant isolates displayed changes in their patterns of susceptibility to antimicrobial compounds. Food industry biocides are effective against planktonicSalmonella. When exposed to sublethal concentrations of individual active biocidal agents, tolerant isolates may emerge. This emergence was associated with changes in antimicrobial susceptibilities.

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Effect of Essential Oils on the Inhibition of Biofilm and Quorum Sensing in Salmonella Enteritidis 13076 and Salmonella Typhimurium 14028

Antibiotics ◽

10.3390/antibiotics10101191 ◽

2021 ◽

Vol 10 (10) ◽

pp. 1191

Author(s):

Yuliany Guillín ◽

Marlon Cáceres ◽

Rodrigo Torres ◽

Elena Stashenko ◽

Claudia Ortiz

Keyword(s):

Quorum Sensing ◽

Essential Oils ◽

Salmonella Enterica ◽

Salmonella Enteritidis ◽

Antimicrobial Agents ◽

Multidrug Resistant ◽

Transcriptional Analysis ◽

Bacterial Cells ◽

Sem Images ◽

Biofilm Inhibition

The emergence of multidrug-resistant microorganisms represents a global challenge that has led to a search for new antimicrobial compounds. Essential oils (EOs) from medicinal aromatic plants are a potential alternative for conventional antibiotics. In this study, the antimicrobial and anti-biofilm potential of 15 EOs was evaluated on planktonic and biofilm-associated cells of Salmonella enterica serovar Enteritidis ATCC 13076 (S. enteritidis) and Salmonella enterica serovar Typhimurium ATCC 14028 (S. typhimurium). In total, 4 out of 15 EOs showed antimicrobial activity and 6 EOs showed anti-biofilm activity against both strains. The EO from the Lippia origanoides chemotype thymol-carvacrol II (LTC II) presented the lowest minimum inhibitory concentration (MIC50 = 0.37 mg mL−1) and minimum bactericidal concentration (MBC = 0.75 mg mL−1) values. This EO also presented the highest percentage of biofilm inhibition (>65%) on both microorganisms, which could be confirmed by scanning electron microscopy (SEM) images. Transcriptional analysis showed significant changes in the expression of the genes related to quorum sensing and the formation of the biofilm. EOs could inhibit the expression of genes involved in the quorum sensing mechanism (luxR, luxS, qseB, sdiA) and biofilm formation (csgA, csgB, csgD, flhD, fliZ, and motB), indicating their potential use as anti-biofilm antimicrobial agents. However, further studies are needed to elucidate the action mechanisms of essential oils on the bacterial cells under study.

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Experimental Induction of Bacterial Resistance to the Antimicrobial Peptide Tachyplesin I and Investigation of the Resistance Mechanisms

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00640-16 ◽

2016 ◽

Vol 60 (10) ◽

pp. 6067-6075 ◽

Cited By ~ 21

Author(s):

Jun Hong ◽

Jianye Hu ◽

Fei Ke

Keyword(s):

Antimicrobial Peptide ◽

Bacterial Resistance ◽

Antimicrobial Agents ◽

Resistance Mechanisms ◽

Cross Resistance ◽

Antibacterial Drug ◽

Cationic Antimicrobial Peptide ◽

Content Type ◽

Tachyplesin I

ABSTRACTTachyplesin I is a 17-amino-acid cationic antimicrobial peptide (AMP) with a typical cyclic antiparallel β-sheet structure that is a promising therapeutic for infections, tumors, and viruses. To date, no bacterial resistance to tachyplesin I has been reported. To explore the safety of tachyplesin I as an antibacterial drug for wide clinical application, we experimentally induced bacterial resistance to tachyplesin I by using two selection procedures and studied the preliminary resistance mechanisms.Aeromonas hydrophilaXS91-4-1,Pseudomonas aeruginosaCGMCC1.2620, andEscherichia coliATCC 25922 and F41 showed resistance to tachyplesin I under long-term selection pressure with continuously increasing concentrations of tachyplesin I. In addition,P. aeruginosaandE. coliexhibited resistance to tachyplesin I under UV mutagenesis selection conditions. Cell growth and colony morphology were slightly different between control strains and strains with induced resistance. Cross-resistance to tachyplesin I and antimicrobial agents (cefoperazone and amikacin) or other AMPs (pexiganan, tachyplesin III, and polyphemusin I) was observed in some resistant mutants. Previous studies showed that extracellular protease-mediated degradation of AMPs induced bacterial resistance to AMPs. Our results indicated that the resistance mechanism ofP. aeruginosawas not entirely dependent on extracellular proteolytic degradation of tachyplesin I; however, tachyplesin I could induce increased proteolytic activity inP. aeruginosa. Most importantly, our findings raise serious concerns about the long-term risks associated with the development and clinical use of tachyplesin I.

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Antibodies Are Major Drivers of Protection against Lethal Aerosol Infection with Highly Pathogenic Burkholderia spp.

mSphere ◽

10.1128/msphere.00674-18 ◽

2019 ◽

Vol 4 (1) ◽

Cited By ~ 1

Author(s):

Robert J. Hogan ◽

Eric R. Lafontaine

Keyword(s):

Public Health ◽

Burkholderia Pseudomallei ◽

Pathogenic Bacteria ◽

Cross Protection ◽

Burkholderia Mallei ◽

Global Public Health ◽

Highly Pathogenic ◽

Content Type ◽

Causative Agents ◽

Aerosol Infection

ABSTRACT Burkholderia pseudomallei and Burkholderia mallei are the causative agents of melioidosis and glanders, respectively. There is no vaccine to protect against these highly pathogenic bacteria, and there is concern regarding their emergence as global public health (B. pseudomallei) and biosecurity (B. mallei) threats. In this issue of mSphere, an article by Khakhum and colleagues (N. Khakhum, P. Bharaj, J. N. Myers, D. Tapia, et al., mSphere 4:e00570-18, 2019, https://doi.org/10.1128/mSphere.00570-18) describes a novel vaccination platform with excellent potential for cross-protection against both Burkholderia species. The report also highlights the importance of antibodies in immunity against these facultative intracellular organisms.

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Evaluation of Aerated Steam Treatment of Alfalfa and Mung Bean Seeds To Eliminate High Levels of Escherichia coli O157:H7 and O178:H12, Salmonella enterica, and Listeria monocytogenes

Applied and Environmental Microbiology ◽

10.1128/aem.00443-13 ◽

2013 ◽

Vol 79 (15) ◽

pp. 4613-4619 ◽

Cited By ~ 14

Author(s):

Patrick Studer ◽

Werner E. Heller ◽

Jörg Hummerjohann ◽

David Drissner

Keyword(s):

Escherichia Coli ◽

Listeria Monocytogenes ◽

Salmonella Enterica ◽

Mung Bean ◽

Germination Rate ◽

Steam Treatment ◽

Heat Sensitivity ◽

Human Pathogens ◽

Content Type ◽

E Coli

ABSTRACTSprouts contaminated with human pathogens are able to cause food-borne diseases due to the favorable growth conditions for bacteria during germination and because of minimal processing steps prior to consumption. We have investigated the potential of hot humid air, i.e., aerated steam, to treat alfalfa and mung bean seeds which have been artificially contaminated withEscherichia coliO157:H7,Salmonella entericasubsp.entericaserovar Weltevreden, andListeria monocytogenesScott A. In addition, a recently collectedE. coliO178:H12 isolate, characterized by a reduced heat sensitivity, was exposed to the treatment described. Populations ofE. coliO157:H7 andS. entericaon alfalfa and mung bean seeds could be completely eliminated by a 300-s treatment with steam at 70 ± 1°C as revealed by enrichment studies.L. monocytogenesandE. coliO178:H12 could not be completely eliminated from artificially inoculated seeds. However, bacterial populations were reduced by more than 5 log CFU/g on alfalfa and by more than 4 log CFU/g on mung bean seeds. The germination rate of mung beans was not affected by the 300-s treatment compared to the germination rate of untreated seeds whereas that of alfalfa seeds was significantly lower by 11.9%. This chemical-free method is an effective alternative to the 20,000-ppm hypochlorite treatment presently recommended by the U.S. Food and Drug Administration (FDA).

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Antimicrobial Resistance in Salmonella in the United States from 1948 to 1995

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02536-15 ◽

2016 ◽

Vol 60 (4) ◽

pp. 2567-2571 ◽

Cited By ~ 17

Author(s):

Daniel A. Tadesse ◽

Aparna Singh ◽

Shaohua Zhao ◽

Mary Bartholomew ◽

Niketta Womack ◽

...

Keyword(s):

United States ◽

Retrospective Study ◽

Multidrug Resistance ◽

Antimicrobial Resistance ◽

Salmonella Enterica ◽

Antimicrobial Agents ◽

The United States ◽

Content Type ◽

The Past ◽

The 1950S

ABSTRACTWe conducted a retrospective study of 2,149 clinicalSalmonellastrains to help document the historical emergence of antimicrobial resistance. There were significant increases in resistance to older drugs, including ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline, which were most common inSalmonella entericaserotype Typhimurium. An increase in multidrug resistance was observed for each decade since the 1950s. These data help show howSalmonellaevolved over the past 6 decades, after the introduction of new antimicrobial agents.

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Fate of Salmonella enterica and Enterohemorrhagic Escherichia coli Cells Artificially Internalized into Vegetable Seeds during Germination

Applied and Environmental Microbiology ◽

10.1128/aem.01888-17 ◽

2017 ◽

Vol 84 (1) ◽

Cited By ~ 9

Author(s):

Da Liu ◽

Yue Cui ◽

Ronald Walcott ◽

Jinru Chen

Keyword(s):

Escherichia Coli ◽

Salmonella Enterica ◽

Bacterial Pathogens ◽

Bacterial Species ◽

Enterohemorrhagic Escherichia Coli ◽

Human Pathogens ◽

Gastrointestinal Infections ◽

Tissue Samples ◽

Content Type ◽

Vegetable Seed

ABSTRACTVegetable seeds contaminated with bacterial pathogens have been linked to fresh-produce-associated outbreaks of gastrointestinal infections. This study was undertaken to observe the physiological behavior ofSalmonella entericaand enterohemorrhagicEscherichia coli(EHEC) cells artificially internalized into vegetable seeds during the germination process. Surface-decontaminated seeds of alfalfa, fenugreek, lettuce, and tomato were vacuum-infiltrated with four individual strains ofSalmonellaor EHEC. Contaminated seeds were germinated at 25°C for 9 days, and different sprout/seedling tissues were microbiologically analyzed every other day. The internalization ofSalmonellaand EHEC cells into vegetable seeds was confirmed by the absence of pathogens in seed-rinsing water and the presence of pathogens in seed homogenates after postinternalization seed surface decontamination. Results show that 317 (62%) and 343 (67%) of the 512 collected sprout/seedling tissue samples were positive forSalmonellaand EHEC, respectively. The averageSalmonellapopulations were significantly larger (P< 0.05) than the EHEC populations. Significantly largerSalmonellapopulations were recovered from the cotyledon and seed coat tissues, followed by the root tissues, but the mean EHEC populations from all sampled tissue sections were statistically similar, except in pregerminated seeds. ThreeSalmonellaand two EHEC strains had significantly larger cell populations on sprout/seedling tissues than other strains used in the study.Salmonellaand EHEC populations from fenugreek and alfalfa tissues were significantly larger than those from tomato and lettuce tissues. The study showed the fate of internalized human pathogens on germinating vegetable seeds and sprout/seedling tissues and emphasized the importance of using pathogen-free seeds for sprout production.IMPORTANCEThe internalization of microorganisms into vegetable seeds could occur naturally and represents a possible pathway of vegetable seed contamination by human pathogens. The present study investigated the ability of two important bacterial pathogens,Salmonellaand enterohemorrhagicEscherichia coli(EHEC), when artificially internalized into vegetable seeds, to grow and disseminate along vegetable sprouts/seedlings during germination. The data from the study revealed that the pathogen cells artificially internalized into vegetable seeds caused the contamination of different tissues of sprouts/seedlings and that pathogen growth on germinating seeds is bacterial species and vegetable seed-type dependent. These results further stress the necessity of using pathogen-free vegetable seeds for edible sprout production.

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