scholarly journals Effect of Non-Thermal Atmospheric Plasma on Food-Borne Bacterial Pathogens on Ready-to Eat Foods: Morphological and Physico-Chemical Changes Occurring on the Cellular Envelopes

Foods ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1865
Author(s):  
Tamara Calvo ◽  
Miguel Prieto ◽  
Avelino Alvarez-Ordóñez ◽  
Mercedes López
Keyword(s):  
Salmonella Enteritidis ◽  
Structural Changes ◽  
Membrane Integrity ◽  
Atmospheric Plasma ◽  
Bacterial Cells ◽  
Bacterial Inactivation ◽  
Cellular Targets ◽  
E Coli ◽  
Physico Chemical ◽  
Potential Applications

Currently, there is a need for new technological interventions to guarantee the microbiological safety of ready-to-eat (RTE) foods. Non-thermal atmospheric plasma (NTAP) has emerged as a promising strategy for inactivating microorganisms on thermo-sensitive foods, and the elucidation of its mechanisms of action will aid the rational optimization and industrial implementation of this technology for potential applications in the food industry. In this study, the effectiveness of NTAP for inactivating strains of Salmonella Enteritidis, Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes contaminating the surface of different sliced RTE foods (“chorizo”, salami, bacon, smoked salmon, tofu and apple) was investigated. In addition, to further assess the bacterial inactivation mechanisms of NTAP, the morphological and physico-chemical damages in bacterial cells were analyzed. NTAP was effective for the surface decontamination of all products tested and, especially, of cut apple, where the microbial populations were reduced between 1.3 and 1.8 log units for the two Salmonella strains and E. coli O157: H7, respectively, after 15 min of exposure. In the rest of foods, no significant differences in the lethality obtained for the E. coli O157:H7 strain were observed, with inactivation rates of between 0.6 and 0.9 log cycles after a 15-min treatment. On the other hand, the strains from the rest of pathogenic microorganisms studied were extremely resistant on tofu, where barely 0.2–0.5 log units of inactivation were achieved after 15 min of plasma exposure. S. Enteritidis cells treated for 10 min exhibited noticeable morphological and structural changes, as observed by transmission electron microscopy, which were accompanied by a loss in membrane integrity, with an increased leakage of intracellular components and uptake of propidium iodide and marked changes in regions of their FTIR spectra indicating major alterations of the cell wall components. Overall, this indicates that loss of viability was likely caused for this microorganism by a significant damage in the cellular envelopes. However, the plasma-treated cells of L. monocytogenes did not show such obvious changes in morphology, and exhibited less marked effects on the integrity of their cytoplasmic membrane, what suggests that the death of this pathogenic microorganism upon NTAP exposure is more likely to occur as a consequence of damages in other cellular targets.

scholarly journals Plasma-Activated Water (PAW) as a Disinfection Technology for Bacterial Inactivation with a Focus on Fruit and Vegetables

Foods ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 166
Author(s):  
Aswathi Soni ◽  
Jonghyun Choi ◽  
Gale Brightwell
Keyword(s):  
Fruit And Vegetables ◽  
Atmospheric Plasma ◽  
Model Systems ◽  
Thermal Treatments ◽  
Bacterial Cells ◽  
Bacterial Inactivation ◽  
Gas Temperature ◽  
Bacterial Strains ◽  
Sensory Qualities ◽  
Plasma Activated Water

Plasma-activated water (PAW) is generated by treating water with cold atmospheric plasma (CAP) using controllable parameters, such as plasma-forming voltage, carrier gas, temperature, pulses, or frequency as required. PAW is reported to have lower pH, higher conductivity, and higher oxygen reduction potential when compared with untreated water due to the presence of reactive species. PAW has received significant attention from researchers over the last decade due to its non-thermal and non-toxic mode of action especially for bacterial inactivation. The objective of the current review is to develop a summary of the effect of PAW on bacterial strains in foods as well as model systems such as buffers, with a specific focus on fruit and vegetables. The review elaborated the properties of PAW, the effect of various treatment parameters on its efficiency in bacterial inactivation along with its usage as a standalone technology as well as a hurdle approach with mild thermal treatments. A section highlighting different models that can be employed to generate PAW alongside a direct comparison of the PAW characteristics on the inactivation potential and the existing research gaps are also included. The mechanism of action of PAW on the bacterial cells and any reported effects on the sensory qualities and shelf life of food has been evaluated. Based on the literature, it can be concluded that PAW offers a significant potential as a non-chemical and non-thermal intervention for bacterial inactivation, especially on food. However, the applicability and usage of PAW depend on the effect of environmental and bacterial strain-based conditions and cost-effectiveness.

scholarly journals Evaluation of treatment and disinfection of water using cold atmospheric plasma

2016 ◽  
Vol 14 (4) ◽  
pp. 609-616 ◽  
Author(s):  
Zohreh Rashmei ◽  
Hamid Bornasi ◽  
Mahmood Ghoranneviss
Keyword(s):  
Atmospheric Plasma ◽  
Bacterial Inactivation ◽  
Electrical Fields ◽  
E Coli ◽  
Colony Forming Units ◽  
Escherichia Coli Bacteria ◽  
Physical And Chemical ◽  
Inactivation Of Bacteria ◽  
Number Of Bacteria ◽  
Research Show

In this paper, the disinfection of water is investigated using plasma spark treatment and the results are compared with conventional techniques. Inactivation of the Enterococcus faecalis and Escherichia coli bacteria is considered in the treatment process of water by the plasma spark. For this purpose, many physical and chemical parameters of water are measured and the obtained results demonstrate a reduction of 8-log in colony forming units of E. coli and E. faecalis at 15 minutes and 12 minutes, respectively. The results of this research show that no ozone is produced during the plasma spark treatment. Moreover, inactivation of a large number of bacteria without any change of pH shows that pH is not the cause of the bacterial inactivation. It is concluded that the main causes of the inactivation of bacteria in the treated water are H2O2 molecules and the electrical fields generated by plasma.

Inactivation of Escherichia Coli 0157:H7 and Salmonella Enteritidis in Liquid Egg Using Continuous Pulsed Electric Field System

2006 ◽  
Vol 1 (5) ◽  
Author(s):  
Malek Amiali ◽  
Michael Ngadi ◽  
James P. Smith ◽  
Vijaya Raghavan
Keyword(s):  
Escherichia Coli ◽  
Electric Field ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
Salmonella Enteritidis ◽  
Processing Temperature ◽  
Bacterial Inactivation ◽  
E Coli ◽  
Liquid Whole Egg ◽  
Whole Egg

This study sought to evaluate the effect of PEF parameters such as electric field intensity and number of pulses on the inactivation of Escherichia coli O157:H7 and Salmonella Enteritidis suspended in liquid whole egg. The medium was inoculated with 108 CFU ml-1 of E. coli O157:H7 or S. Enteritidis and was treated continuously at 10, 20 or 30°C using electric field intensity of either 20 or 30 kV cm-1. A biphasic instant reversal PEF waveform with up to 105 pulses of 2 µs in width was applied. Bacterial inactivation increased with increasing applied electric field intensity, number of pulses and processing temperature. Maximum reductions of 3.9 and 3.6 log cycles were obtained for E. coli O157:H7 and S. Enteritidis, respectively. The maximum input energies required to inactivate E. coli O157:H7 and S. Enteritidis were 538 and 914 J, respectively. The higher kinetic value was obtained for S. Enteritidis (0.043 µs-1) representing the more heat–PEF sensitive bacteria compared to E. coli O157:H7.

Formation of ammonium in saline solution treated by nanosecond pulsed cold atmospheric microplasma: a route to fast inactivation of E. coli bacteria

RSC Advances ◽  
2015 ◽  
Vol 5 (52) ◽  
pp. 42135-42140 ◽  
Author(s):  
Simon Maheux ◽  
David Duday ◽  
Thierry Belmonte ◽  
Christian Penny ◽  
Henry-Michel Cauchie ◽  
...  
Keyword(s):  
Saline Solution ◽  
Atmospheric Plasma ◽  
Main Process ◽  
Bacterial Inactivation ◽  
Fast Inactivation ◽  
Cold Atmospheric Plasma ◽  
E Coli ◽  
Solution Treated ◽  
Saline Solutions ◽  
First Time

The formation of significant NH4+species in saline solutions treated by He/N2cold atmospheric plasma is proposed for the first time as the main process responsible for the fast bacterial inactivation ofE. coliat ambient temperature and physiological pH.

scholarly journals Synergistic Antibiofilm Effects of Ultrasound and Phenyllactic Acid against Staphylococcus aureus and Salmonella enteritidis

Foods ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2171
Author(s):  
Jiaojiao Zhang ◽  
Debao Wang ◽  
Jinyue Sun ◽  
Zhilan Sun ◽  
Fang Liu ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Respiratory Chain ◽  
Laser Scanning ◽  
Salmonella Enteritidis ◽  
Membrane Integrity ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Bacterial Cells ◽  
Phenyllactic Acid ◽  
Cell Membrane Integrity

This study evaluated the effect of the combination of ultrasound and phenyllactic acid (PLA) on inactivating Staphylococcus aureus and Salmonella enteritidis biofilm cells and determined the possible antibiofilm mechanism. S. aureus and S. enteritidis biofilm cells were separately treated with ultrasound (US, 270 W), phenyllactic acid (PLA, 0.5% and 1%), and their combination (US + 0.5% PLA, and US + 1% PLA) for 5, 10, 20, 30, and 60 min. Biofilm inactivation, polysaccharide, and respiratory chain dehydrogenase assays were conducted. US and PLA had a synergistic effect on inactivating bacterial cells in S. aureus and S. enteritidis biofilms. The combination of US and PLA significantly decreased the contents of soluble and insoluble polysaccharides and the activity of respiratory chain dehydrogenase in the biofilm cells compared to the single treatment. Confocal laser scanning microscopy, scanning electron microscopy, and intracellular adenosine-triphosphate (ATP) analyses indicated that the combination of US and PLA seriously destroyed the cell membrane integrity of the S. aureus and S. enteritidis biofilms and caused the leakage of intracellular ATP. These findings demonstrated the synergistic antibiofilm effect of US combined with PLA and offered a research basis for its application in the food industry.

scholarly journals Killing of adherent oral microbes by a non-thermal atmospheric plasma jet

2010 ◽  
Vol 59 (2) ◽  
pp. 206-212 ◽  
Author(s):  
Stefan Rupf ◽  
Antje Lehmann ◽  
Matthias Hannig ◽  
Barbara Schäfer ◽  
Andreas Schubert ◽  
...  
Keyword(s):  
Plasma Jet ◽  
Plasma Jets ◽  
Atmospheric Plasma ◽  
Killing Effect ◽  
E Coli ◽  
Potential Applications ◽  
Oral Microbes ◽  
Micro Organisms

Atmospheric plasma jets are being intensively studied with respect to potential applications in medicine. The aim of this in vitro study was to test a microwave-powered non-thermal atmospheric plasma jet for its antimicrobial efficacy against adherent oral micro-organisms. Agar plates and dentin slices were inoculated with 6 log10 c.f.u. cm−2 of Lactobacillus casei, Streptococcus mutans and Candida albicans, with Escherichia coli as a control. Areas of 1 cm2 on the agar plates or the complete dentin slices were irradiated with a helium plasma jet for 0.3, 0.6 or 0.9 s mm−2, respectively. The agar plates were incubated at 37 °C, and dentin slices were vortexed in liquid media and suspensions were placed on agar plates. The killing efficacy of the plasma jet was assessed by counting the number of c.f.u. on the irradiated areas of the agar plates, as well as by determination of the number of c.f.u. recovered from dentin slices. A microbe-killing effect was found on the irradiated parts of the agar plates for L. casei, S. mutans, C. albicans and E. coli. The plasma-jet treatment reduced the c.f.u. by 3–4 log10 intervals on the dentin slices in comparison to recovery rates from untreated controls. The microbe-killing effect was correlated with increasing irradiation times. Thus, non-thermal atmospheric plasma jets could be used for the disinfection of dental surfaces.

scholarly journals ssDNA recombineering boosts in vivo evolution of nanobodies displayed on bacterial surfaces

2021 ◽  
Author(s):  
Yamal Al-ramahi ◽  
Akos Nyerges ◽  
Yago Margolles ◽  
Lidia Cerdán ◽  
Gyorgyi Ferenc ◽  
...  
Keyword(s):  
Bacterial Genome ◽  
Industrial Biotechnology ◽  
Bacterial Cells ◽  
E Coli ◽  
Immunomagnetic Capture ◽  
Bacterial Surfaces ◽  
Potential Applications ◽  
Novel Target

SUMMARYIn vivo evolution of antibodies facilitates emergence of novel target specificities from pre-existing clones. In this work we show how mutagenic ssDNA recombineering of camel-derived nanobodies encoded in a bacterial genome enables clonal hyper-diversification and the rise of new properties. As a proof-of-principle we used a nanobody recognizing the antigen TirM from enterohaemorrhagic E. coli (EHEC) and evolved it towards the otherwise not recognized TirM antigen from enteropathogenic E. coli (EPEC). To this end, E. coli cells displaying on their surface this nanobody fused to the intimin outer membrane anchor domain were subjected to multiple rounds of mutagenic ssDNA recombineering targeted to the CDR1, CDR2 and CDR3 regions of its genomically encoded VHH sequence. Binders to the new antigen (EPEC TirM) were then selected upon immunomagnetic capture of bacteria bearing the corresponding nanobody variants. As a result, several modified nanobodies were identified which maintained recognition of EHEC TirM but acquired the ability to bind the new antigen with high affinity (Kd ~20 nM). The results highlight the power of combining evolutionary properties of bacteria in vivo with oligonucleotide synthesis in vitro for the sake of focusing diversification to specific segments of a gene (or protein thereof) of interest. Our experimental workflow empowers the evolution of nanobodies displayed on the surface of bacterial cells for a large number of potential applications in medical and industrial biotechnology.

Evaluation of Universal Preenrichment Broth for Growth of Heat-Injured Pathogens

2001 ◽  
Vol 64 (11) ◽  
pp. 1751-1755 ◽  
Author(s):  
TONG ZHAO ◽  
MICHAEL P. DOYLE
Keyword(s):  
Salmonella Typhimurium ◽  
Salmonella Enterica ◽  
Salmonella Enteritidis ◽  
Ground Beef ◽  
Detection Methods ◽  
Cell Populations ◽  
Bacterial Cells ◽  
E Coli ◽  
Enrichment Cultures ◽  
Cell Counts

Universal preenrichment broth (UPB) was developed to enable enrichment of injured foodborne pathogens of different genera simultaneously in lieu of having to undergo separate simultaneous enrichment cultures for subsequent detection or isolation of each pathogen. Enrichment conditions in UPB for growth of injured pathogens to populations that will enable pathogen detection by rapid immuno-based or polymerase chain reaction (PCR)-based assays have not been defined. Hence, studies were done to determine recovery and growth rates of heat-injured Escherichia coli O157:H7, Salmonella enterica ser. Typhimurium, Salmonella enterica ser. Enteritidis, and Listeria monocytogenes in UPB. Bacterial cells were heat injured in tryptic phosphate broth at 57.2°C and inoculated at populations of ca. 0.17 to 63 injured cells per ml with raw ground beef, fresh chicken, lettuce, and environmental sponge samples. Enrichment cultures were sampled at 1, 2, 3, 4, 5, 6, and 24 h at 37°C postinoculation, and pathogens were enumerated on appropriate selective media. Results revealed that recovery and growth of pathogens during the first 6 h of enrichment were not sufficient to ensure adequate numbers of bacteria (>103 CFU/ml) for detection by most immunoassays or PCR assays. Cells often required 3 to 4 h for recovery before growth was initiated. Salmonella Typhimurium, Salmonella Enteritidis, E. coli O157:H7, or L. monocytogenes cell populations in enrichment cultures with ground beef or lettuce at 6 h were 0.5 to 2.9 log10 CFU/ml. At 24 h of incubation, cell counts of enrichment samples for the three pathogens from all food and environmental sponge samples ranged from 4.0 to 8.3 log10 CFU/ml. Enrichment in UPB at 37°C of foods or environmental sponge samples containing heat-injured cells of Salmonella Typhimurium, Salmonella Enteritidis, E. coli O157:H7, or L. monocytogenes reliably provides at 24 h of incubation—but not at 6 h—sufficient cell populations for detection by rapid immunoassay or PCR assay procedures that can detect at least 4 log10 CFU/ml. These results raise questions regarding the sensitivity of rapid detection methods that employ an abbreviated enrichment protocol of 6 h or less.

scholarly journals Effects of Lipopolysaccharide Core Sugar Deficiency on Colanic Acid Biosynthesis in Escherichia coli

2016 ◽  
Vol 198 (11) ◽  
pp. 1576-1584 ◽  
Author(s):  
Ge Ren ◽  
Zhou Wang ◽  
Ye Li ◽  
Xiaoqing Hu ◽  
Xiaoyuan Wang
Keyword(s):  
Escherichia Coli ◽  
Acid Production ◽  
High Performance ◽  
Membrane Integrity ◽  
Biological Significance ◽  
Bacterial Cells ◽  
Content Type ◽  
E Coli ◽  
Colanic Acid ◽  
Cell Stress Response

ABSTRACTWhen 10Escherichia colimutant strains with defects in lipopolysaccharide (LPS) core biosynthesis were grown on agar medium at 30°C, four of them, the ΔwaaF, ΔwaaG, ΔwaaP, and ΔwaaBstrains, formed mucoid colonies, while the other six, the ΔwaaU, ΔwaaR, ΔwaaO, ΔwaaC, ΔwaaQ, and ΔwaaYstrains, did not. Using light microscopy with tannin mordant staining, the presence of exopolysaccharide around the cells of the mutants that formed mucoid colonies could be discerned. The ΔwaaFmutant produced the largest amounts of exopolysaccharide, regardless of whether it was grown on agar or in liquid medium. The exopolysaccharide was isolated from the liquid growth medium of ΔwaaFcells, hydrolyzed, and analyzed by high-performance liquid chromatography with an ion-exchange column, and the results indicated that the exopolysaccharide was consistent with colanic acid. When the key genes related to the biosynthesis of colanic acid, i.e.,wza,wzb,wzc, andwcaA, were deleted in the ΔwaaFbackground, the exopolysaccharide could not be produced any more, further confirming that it was colanic acid. Colanic acid could not be produced in strains in whichrcsA,rcsB,rcsD, orrcsFwas deleted in the ΔwaaFbackground, but a reduced level of colanic acid production was detected when thercsCgene was deleted, suggesting that a change of lipopolysaccharide structure in ΔwaaFcells might be sensed by the RcsCDB phosphorelay system, leading to the production of colanic acid. The results demonstrate thatE. colicells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural deficiency of lipopolysaccharide.IMPORTANCELipopolysaccharide and colanic acid are important forms of exopolysaccharide forEscherichia colicells. Their metabolism and biological significance have been investigated, but their interrelation with the cell stress response process is not understood. This study demonstrates, for the first time, thatE. colicells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural change of lipopolysaccharide, suggesting that bacterial cells can monitor the outer membrane integrity, which is essential for cell survival and damage repair.

scholarly journals Combined Antimicrobial Effect of Bio-Waste Olive Leaf Extract and Remote Cold Atmospheric Plasma Effluent

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1890
Author(s):  
Jose Gustavo De la Ossa ◽  
Hani El Kadri ◽  
Jorge Gutierrez-Merino ◽  
Thomas Wantock ◽  
Thomas Harle ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Leaf Extract ◽  
Preliminary Investigation ◽  
Atmospheric Plasma ◽  
Aureus Strain ◽  
Bacterial Inactivation ◽  
Olive Leaf ◽  
Cold Atmospheric Plasma ◽  
E Coli ◽  
Olive Leaf Extract

A novel strategy involving Olive Leaf Extract (OLE) and Cold Atmospheric Plasma (CAP) was developed as a green antimicrobial treatment. Specifically, we reported a preliminary investigation on the combined use of OLE + CAP against three pathogens, chosen to represent medical and food industries (i.e., E. coli, S. aureus and L. innocua). The results indicated that a concentration of 100 mg/mL (total polyphenols) in OLE can exert an antimicrobial activity, but still insufficient for a total bacterial inactivation. By using plain OLE, we significantly reduced the growth of Gram positive S. aureus and L. innocua, but not Gram-negative E. coli. Instead, we demonstrated a remarkable decontamination effect of OLE + CAP in E. coli, S. aureus and L. innocua samples after 6 h. This effect was optimally maintained up to 24 h in S. aureus strain. E. coli and L. innocua grew again in 24 h. In the latter strain, OLE alone was most effective to significantly reduce bacterial growth. By further adjusting the parameters of OLE + CAP technology, e.g., OLE amount and CAP exposure, it could be possible to prolong the initial powerful decontamination over a longer time. Since OLE derives from a bio-waste and CAP is a non-thermal technology based on ionized air, we propose OLE + CAP as a potential green platform for bacterial decontamination. As a combination, OLE and CAP can lead to better antimicrobial activity than individually and may replace or complement conventional thermal procedures in food and biomedical industries.

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