scholarly journals Antibacterial activity of selected varieties of Malaysian honey against Escherichia coli: A comparative study

10.3823/854 ◽  
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad A. Alkafaween ◽  
Hamid A. Nagi Al-Jamal ◽  
Abu Bakar Mohmd Hilmi
Keyword(s):  
Escherichia Coli ◽  
Antibacterial Activity ◽  
Expression Profiles ◽  
E Coli ◽  
Log Reduction ◽  
Qpcr Analysis ◽  
Acacia Honey ◽  
Kill Curve ◽  
Time Kill ◽  
Tualang Honey

Background: The purpose of this study was to investigate antibacterial activity of three varieties of Malaysian honey; Tualang honey (TH), Gelam honey (GH), and Acacia honey (AH) against Escherichia coli. Methods: The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the honey samples against E. coli were determined by the broth microdilution assay in the presence and absence of catalase enzyme. The mode of inhibition of honey samples against E. coli was investigated by the effect of time on viability. Impacts of the honeys on the expression profiles of the selected genes of E. coli were examined using RT-qPCR analysis. Results: The results showed that TH and GH honey possessed lowest MIC and MBC values against E. coli with 20% and 25% (w/v) respectively. Highest MIC and MBC values were observed by AH honey against E. coli with 25% (w/v) and 50% (w/v) values respectively. Among the tested honeys, TH and GH exhibited the highest total antibacterial activity and the highest levels of peroxide-dependent activity. Time–kill curve demonstrated a bactericidal rather than a bacteriostatic effect; with a 2-log reduction estimated within 540 min. Viable cells were not recovered after 9 hours exposure to MIC of all honey-treated. The RT-qPCR analysis showed that all honey-treated cells share a similar overall pattern of gene expression, with a trend toward reduced expression of the virulence genes of interest. Conclusion: This study demonstrates that Malaysian honey have the potential to be effective inhibitor and virulence modulator of E. coli via multiple molecular targets.

scholarly journals Antibacterial Activity of Ethanolic Extract ofSyzygium polyanthumL.(Salam)Leaves against Foodborne Pathogens and Application as Food Sanitizer

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Suzita Ramli ◽  
Son Radu ◽  
Khozirah Shaari ◽  
Yaya Rukayadi
Keyword(s):  
Antibacterial Activity ◽  
Foodborne Pathogens ◽  
Ethanolic Extract ◽  
Inhibition Zone ◽  
Antimicrobial Activities ◽  
Disk Diffusion Test ◽  
E Coli ◽  
Natural Microflora ◽  
Kill Curve ◽  
Time Kill

The aim of this study was to determine antibacterial activity ofS. polyanthumL.(salam)leaves extract foodborne pathogens. All the foodborne pathogens were inhibited after treating with extract in disk diffusion test with range6.67±0.58–9.67±0.58 mm of inhibition zone. The range of MIC values was between 0.63 and 1.25 mg/mL whereas MBC values were in the range 0.63 mg/mL to 2.50 mg/mL. In time-kill curve,L. monocytogenesandP. aeruginosawere found completely killed after exposing to extract in 1 h incubation at 4x MIC. Four hours had been taken to completely killE. coli,S. aureus,V. cholerae,andV. parahaemolyticusat 4x MIC. However, the population ofK. pneumoniae,P. mirabilis,andS. typhimuriumonly reduced to 3 log CFU/mL. The treated cell showed cell rupture and leakage of the cell cytoplasm in SEM observation. The significant reduction of natural microflora in grapes fruit was started at 0.50% of extract at 5 min and this concentration also was parallel to sensory attributes acceptability where application of extract was accepted by the panellists until 5%. In conclusion,S. polyanthumextract exhibits antimicrobial activities and thus might be developed as natural sanitizer for washing raw food materials.

scholarly journals Time-kill kinetics and antibacterial activity of root extract of Adenodolichos paniculatus (Hua) Hutch & Dalz (Fabaceae)

2021 ◽  
Vol 18 (2) ◽  
pp. 95-102
Author(s):  
Friday I. Kyahar ◽  
Edith A. Onwuliri ◽  
Joseph O. Ehinmidu ◽  
Peters O. Oladosu
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Antibacterial Activity ◽  
Streptococcus Pyogenes ◽  
Antibacterial Activities ◽  
Root Extract ◽  
Log Reduction ◽  
Zones Of Inhibition ◽  
Time Kill

Medicinal plants have been used in treatment of illness from time immemorial. Adenodolichos paniculatus is a medicinal plant used for traditional remedy of sore throat infections. This study therefore, evaluated the antibacterial activities of the root extracts and time-kill kinetics of the most potent extract. Five extracts, obtained by maceration using n-hexane, chloroform, ethyl acetate, methanol and water sequentially were evaluated for antibacterial activities and time-kill kinetics against Streptococcus pyogenes, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. Chloroform root extract at 100 mg/ml was active against Streptococcus pyogenes, Staphylococcus aureus and Pseudomonas aeruginosa with zones of inhibition 25.00, 21.00 and 14.75 mm respectively but not against Escherichia coli. Minimum inhibitory concentrations were 1.56, 6.25 and 25.00 mg/ml respectively and the minimum bactericidal concentrations were 3.12, 12.50 and 50.00 mg/ml. Complete elimination of S. pyogenes, S. aureus and P. aeruginosa was achieved at concentrations 1.56 mg/ml, 6.25 mg/ml and 25.00 mg/ml within 300, 720 and 960 minutes exposure respectively and at concentrations 3.12 mg/ml, 25.00 mg/ml and 50.00 mg/ml within 180, 300 and 720 minutes exposure respectively. Chloroform root extract has the potential to be used as antibacterial agent and was better than the other solvent extract two-fold. Keywords: Adenodolichos paniculatus; Antibacterial activity; Time-kill kinetics; Percentage reduction, Log reduction

Potential Antibacterial Activity of Yemeni Sidr Honey Against Pseudomonas aeruginosa and Streptococcus pyogenes

2021 ◽  
Vol 19 ◽  
Author(s):  
Mohammad A. Al-kafaween ◽  
Abu Bakar Mohd Hilmi ◽  
Hamid A. Nagi Al-Jamal ◽  
Rania M. Al-Groom ◽  
Nour A. Elsahoryi ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Pathogenic Bacteria ◽  
Growth Curves ◽  
Cell Number ◽  
Sem Analysis ◽  
Dilution Method ◽  
Microbial Infection ◽  
Log Reduction ◽  
Kill Curve ◽  
Time Kill

Background: Sidr honey has been reported to exhibit antimicrobial activity against numerous pathogenic bacteria making this honey a promising functional food for the treatment of wounds or stomach ulcers. Objective: The purpose of this study was to investigate the effect of Sidr honey against P. aeruginosa and S. pyogenes. Methods: Minimum inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) for Sidr honey were determined by the broth dilution method. The growth curve of both bacteria with MIC, half-MIC and quarter-MIC were monitored by optical density (at OD570). The time-kill curve was used to determine the bacteriostatic and bactericidal activity of Sidr honey on both bacteria by plotting colony forming unit (CFUs) versus time. The effect of Sidr honey on the ultrastructure of the P. aeruginosa and S. pyogenes was investigated using scanning electron microscopy (SEM). The effect of Sidr honey on the expression of virulence genes in both bacteria was determined using quantitative reverse transcription polymerase chain reaction (RT-qPCR). Results: The results showed that Sidr honey possessed the lowest MIC value against P. aeruginosa and S. pyogenes with 12.5 % (w/v) and 20 % (w/v) respectively. In addition, the MBC value for Sidr honey was found to be 20% (w/v) and 25% (w/v) against P. aeruginosa and S. pyogenes respectively. Growth curves conducted with MIC Sidr honey resulted in no growth of P. aeruginosa and S. pyogenes. Growth curves with half-MIC Sidr honey resulted in a reduced growth rate and reduction in overall cell number in both bacteria over a period of 24 h, compared with cells grown without honey. In time-kill curve, treatment of P. aeruginosa and S. pyogenes with Sidr honey for 8 hours resulted in decreases of 4-log reduction (P < 0.05) in total viable counts (TVCs). SEM analysis revealed that there were marked changes in the bacterial cell morphology for both bacteria following treatment with Sidr honey. These changes included the appearance of irregular shapes, incomplete cell division, and swelling cells. The RT-qPCR results showed that the expression of algD, oprF, fleN, fleQ, fleR, fliA, and fliC in P. aeruginosa decreased 0.43-fold, 0.38-fold, 0.41-fold, 0.51-fold, 0.40-fold, 0.61-fold, and 0.39-fold respectively after exposure to Sidr honey. Meanwhile the expression of sof, sfbl, and scpA in S. pyogenes decreased 0.18-fold, 0.21-fold, and 0.28-fold respectively after treated with Sidr honey. Conclusion: Using varying methods to evaluate the planktonic integrity, this study demonstrated that Sidr honey has antibacterial activity against both bacteria and has potential as a therapeutic agent for microbial infection particularly against these two organisms. To our knowledge, this study is the first to indicate that Sidr honey is effective at inducing cell lysis and identify targets genes, at the genetic level, that might be involved in this process.

scholarly journals Antibacterial properties of selected Malaysian Tualang honey against Pseudomonas aeruginosa and Streptococcus pyogenes

2020 ◽  
Author(s):  
Mohammad Abdulraheem Al-Kafaween ◽  
Hamid Ali Al-Jamal ◽  
Abu Bakar Mohd Hilmi ◽  
Nour Amin Elsahoryi ◽  
Norzawani Jaffar ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Streptococcus Pyogenes ◽  
Structural Integrity ◽  
Antibacterial Properties ◽  
Microbial Infection ◽  
Potential Health ◽  
Log Reduction ◽  
Kill Curve ◽  
Time Kill ◽  
Tualang Honey

Background and Objectives: Tualang honey (TH) is a Malaysian multifloral jungle honey. In recent years, there has been a marked increase in the number of studies published in medical databases regarding its potential health benefits. The study aimed to investigate the effect of TH against Pseudomonas aeruginosa and Streptococcus pyogenes. Materials and Methods: The effect of TH on both bacteria was investigated using MIC, MBC, growth curve, time-kill curve, scanning electron microscopy (SEM) and RT-qPCR. Results: The MIC of TH against P. aeruginosa and S. pyogenes was 18.5% (w/v) and 13% (w/v) respectively and MBC 90 was 25% (w/v) for both bacteria. Spectrophotometric readings of at least 90% inhibition yielded MIC values of TH, 18.5% (w/v) and 15% (w/v) for P. aeruginosa and S. pyogenes respectively. A time–kill curve demonstrated a bactericidal with a 4-log reduction estimated within 8 hours. Using SEM, loss of structural integrity and marked changes in cell shape were observed. RT-qPCR analysis showed that TH reduced the pattern of gene expression in both bacteria, with a trend toward reduced expression of the virulence genes of interest. Conclusion: This study suggests that TH could potentially be used as an alternative therapeutic agent for microbial infection particularly against these two organisms.

scholarly journals Antibacterial properties of Tualang, Acacia and Yemeni Sumur honey against selected food spoilage bacteria and foodborne pathogens

Food Research ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 448-460
Author(s):  
K. Yousof ◽  
Nor-Khaizura M.A.R. ◽  
Nur Hanani Z.A. ◽  
Ismail-Fitry M.R.
Keyword(s):  
Staphylococcus Aureus ◽  
Antibacterial Activity ◽  
Foodborne Pathogens ◽  
Antibacterial Properties ◽  
Bacterial Strains ◽  
Spoilage Bacteria ◽  
Food Isolate ◽  
Acacia Honey ◽  
Time Kill ◽  
Tualang Honey

The antibacterial activity of honey is mainly credited to its acidity, osmolarity and enzymatic generation of hydrogen peroxide via glucose oxidase. Additional honey components, such as aromatic acids or phenolic compounds, also contribute to the overall antibacterial activity. The level of antibacterial activities found in honey varies with different types of honey, due to mainly the composition, percentage as well as the nature of the sugars present in the honey. This study aimed to evaluate the antibacterial activity of four types of honey, namely Tualang honey (TH1), Tualang honey (TH2), Acacia honey (AH) and Yemeni Sumur honey (YSH). Nine bacterial strains were used. Disc diffusion, well diffusion, minimum inhibitory concentration (MIC), Minimum bactericidal concentration (MBC), and time-kill methods were performed to reveal the antibacterial potential of the selected honey. The MIC values ranged between 12.5 to 50% for both TH1 and YSH while for TH2, and AH it ranged between 25 to 50%. For MBC, it ranged from 25 to 50%. The time-kill in TH1 Staphylococcus aureus (food isolate) showed total inhibition at 6 hrs in 2 X MIC, and for Staphylococcus aureus ATCC 29737 was 3.84 log CFU/g at the 6 hrs. Physicochemical quality of honey resulted as follows: the pH of the honey samples was acidic in nature ranging between 3.69 to 3.94, and the aw of the honey samples were between 0.53 to 0.69. For colour analysis, YSH was observed to has the maximum lightness and yellowness, and TH1 has the maximum redness. While, AH had a minimum lightness, redness, and yellowness.

Synthesis of Chalcones and Nucleosides Incorporating [1, 3, 4]Oxadiazolenone Core and Evaluation of their Antifungal and Antibacterial Activities

2020 ◽  
Vol 15 (6) ◽  
pp. 665-679
Author(s):  
Alok K. Srivastava ◽  
Lokesh K. Pandey
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Antibacterial Activity ◽  
Bacillus Subtilis ◽  
Antifungal Activity ◽  
Aspergillus Niger ◽  
Gram Negative ◽  
E Coli ◽  
Gram Positive Bacteria ◽  
Good Antibacterial Activity

Background: [1, 3, 4]oxadiazolenone core containing chalcones and nucleosides were synthesized by Claisen-Schmidt condensation of a variety of benzaldehyde derivatives, obtained from oxidation of substituted 5-(3/6 substituted-4-Methylphenyl)-1, 3, 4-oxadiazole-2(3H)-one and various substituted acetophenone. The resultant chalcones were coupled with penta-O-acetylglucopyranose followed by deacetylation to get [1, 3, 4] oxadiazolenone core containing chalcones and nucleosides. Various analytical techniques viz IR, NMR, LC-MS and elemental analysis were used to confirm the structure of the synthesised compounds.The compounds were targeted against Bacillus subtilis, Staphylococcus aureus and Escherichia coli for antibacterial activity and Aspergillus flavus, Aspergillus niger and Fusarium oxysporum for antifungal activity. Methods: A mixture of Acid hydrazides (3.0 mmol) and N, Nʹ- carbonyl diimidazole (3.3 mmol) in 15 mL of dioxane was refluxed to afford substituted [1, 3, 4]-oxadiazole-2(3H)-one. The resulted [1, 3, 4]- oxadiazole-2(3H)-one (1.42 mmol) was oxidized with Chromyl chloride (1.5 mL) in 20 mL of carbon tetra chloride and condensed with acetophenones (1.42 mmol) to get chalcones 4. The equimolar ratio of obtained chalcones 4 and β -D-1,2,3,4,6- penta-O-acetylglucopyranose in presence of iodine was refluxed to get nucleosides 5. The [1, 3, 4] oxadiazolenone core containing chalcones 4 and nucleosides 5 were tested to determined minimum inhibitory concentration (MIC) value with the experimental procedure of Benson using disc-diffusion method. All compounds were tested at concentration of 5 mg/mL, 2.5 mg/mL, 1.25 mg/mL, 0.62 mg/mL, 0.31 mg/mL and 0.15 mg/mL for antifungal activity against three strains of pathogenic fungi Aspergillus flavus (A. flavus), Aspergillus niger (A. niger) and Fusarium oxysporum (F. oxysporum) and for antibacterial activity against Gram-negative bacterium: Escherichia coli (E. coli), and two Gram-positive bacteria: Staphylococcus aureus (S. aureus) and Bacillus subtilis(B. subtilis). Result: The chalcones 4 and nucleosides 5 were screened for antibacterial activity against E. coli, S. aureus and B. subtilis whereas antifungal activity against A. flavus, A. niger and F. oxysporum. Compounds 4a-t showed good antibacterial activity whereas compounds 5a-t containing glucose moiety showed better activity against fungi. The glucose moiety of compounds 5 helps to enter into the cell wall of fungi and control the cell growth. Conclusion: Chalcones 4 and nucleosides 5 incorporating [1, 3, 4] oxadiazolenone core were synthesized and characterized by various spectral techniques and elemental analysis. These compounds were evaluated for their antifungal activity against three fungi; viz. A. flavus, A. niger and F. oxysporum. In addition to this, synthesized compounds were evaluated for their antibacterial activity against gram negative bacteria E. Coli and gram positive bacteria S. aureus, B. subtilis. Compounds 4a-t showed good antibacterial activity whereas 5a-t showed better activity against fungi.

scholarly journals Proteomic response of Escherichia coli to a membrane lytic and iron chelating truncated Amaranthus tricolor defensin

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Tessa B. Moyer ◽  
Ashleigh L. Purvis ◽  
Andrew J. Wommack ◽  
Leslie M. Hicks
Keyword(s):  
Escherichia Coli ◽  
Antibacterial Activity ◽  
Antimicrobial Peptides ◽  
Mechanism Of Action ◽  
Gram Negative Bacteria ◽  
Amaranthus Tricolor ◽  
Core Motif ◽  
Gram Negative ◽  
E Coli ◽  
Membrane Lysis

Abstract Background Plant defensins are a broadly distributed family of antimicrobial peptides which have been primarily studied for agriculturally relevant antifungal activity. Recent studies have probed defensins against Gram-negative bacteria revealing evidence for multiple mechanisms of action including membrane lysis and ribosomal inhibition. Herein, a truncated synthetic analog containing the γ-core motif of Amaranthus tricolor DEF2 (Atr-DEF2) reveals Gram-negative antibacterial activity and its mechanism of action is probed via proteomics, outer membrane permeability studies, and iron reduction/chelation assays. Results Atr-DEF2(G39-C54) demonstrated activity against two Gram-negative human bacterial pathogens, Escherichia coli and Klebsiella pneumoniae. Quantitative proteomics revealed changes in the E. coli proteome in response to treatment of sub-lethal concentrations of the truncated defensin, including bacterial outer membrane (OM) and iron acquisition/processing related proteins. Modification of OM charge is a common response of Gram-negative bacteria to membrane lytic antimicrobial peptides (AMPs) to reduce electrostatic interactions, and this mechanism of action was confirmed for Atr-DEF2(G39-C54) via an N-phenylnaphthalen-1-amine uptake assay. Additionally, in vitro assays confirmed the capacity of Atr-DEF2(G39-C54) to reduce Fe3+ and chelate Fe2+ at cell culture relevant concentrations, thus limiting the availability of essential enzymatic cofactors. Conclusions This study highlights the utility of plant defensin γ-core motif synthetic analogs for characterization of novel defensin activity. Proteomic changes in E. coli after treatment with Atr-DEF2(G39-C54) supported the hypothesis that membrane lysis is an important component of γ-core motif mediated antibacterial activity but also emphasized that other properties, such as metal sequestration, may contribute to a multifaceted mechanism of action.

Antimicrobial Effects of Novel H2O2-Ag+ Complex on Membrane Damage to Staphylococcus aureus,Escherichia coli and Salmonella typhimurium

2021 ◽  
Author(s):  
Bing Han ◽  
Xiaoyu Han ◽  
Mengmeng Ren ◽  
Yilin You ◽  
Jicheng Zhan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Staphylococcus Aureus ◽  
Salmonella Typhimurium ◽  
Membrane Damage ◽  
Bactericidal Effect ◽  
E Coli ◽  
Bacterial Cell Membrane ◽  
Time Kill ◽  
Environmental Disinfection

Diseases caused by harmful microorganisms pose a serious threat to human health. Safe and environment-friendly disinfectants are, therefore, essential in preventing and controlling such pathogens. This study aimed to investigate the antimicrobial activity and mechanism of a novel hydrogen peroxide and silver (H 2 O 2 -Ag + ) complex (HSC) in combatting Staphylococcus aureus ATCC 29213, Escherichia coli O157:H7 NCTC 12900 and Salmonella typhimurium SL 1344. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against S. aureus were found to be 0.014 % H 2 O 2 -3.125 mg/L Ag + , while 0.028 % H 2 O 2 -6.25 mg/L Ag + for both E. coli and S. typhimurium . Results of the growth curve assay and time-kill trial suggest that the HSC could inhibit the growth of the tested bacteria, as 99.9 % of viable cells were killed following treatment at the 1 MIC for 3 h. Compared with Oxytech D10 disinfectant (0.25 % H 2 O 2 -5 mg/L Ag + ), the HSC exhibited better antibacterial efficacy at a lower concentration (0.045 % H 2 O 2 -10 mg/L Ag + ). The mechanism of antibacterial action of HSC was found including the disruption of the bacterial cell membrane, followed by entry into the bacteria cell to reduce intracellular adenosine triphosphate (ATP) concentration, and inhibit the activity of antioxidases, superoxide dismutase (SOD) and catalase (CAT). The enhanced bactericidal effect of hydrogen peroxide combined with silver indicates a potential for its application in environmental disinfection, particularly in the food industry.

Reduction of Escherichia coli O157:H7 Counts on Whole Fresh Apples by Treatment with Sanitizers

2000 ◽  
Vol 63 (6) ◽  
pp. 703-708 ◽  
Author(s):  
MARCY A. WISNIEWSKY ◽  
BONITA A. GLATZ ◽  
MARK L. GLEASON ◽  
CHERYLL A. REITMEIER
Keyword(s):  
Escherichia Coli ◽  
Chlorine Dioxide ◽  
Phosphate Buffer ◽  
Phosphate Buffer Solution ◽  
Escherichia Coli O157 ◽  
Peroxyacetic Acid ◽  
Water Control ◽  
Buffer Solution ◽  
E Coli ◽  
Log Reduction

The objectives of this study were to determine if washing of whole apples with solutions of three different sanitizers (peroxyacetic acid, chlorine dioxide, or a chlorine-phosphate buffer solution) could reduce a contaminating nonpathogenic Escherichia coli O157:H7 population by 5 logs and at what sanitizer concentration and wash time such a reduction could be achieved. Sanitizers were tested at 1, 2, 4, 8, and 16 times the manufacturer's recommended concentration at wash times of 5, 10, and 15 min. Whole, sound Braeburn apples were inoculated with approximately 1 × 108 or 7 × 106 CFU per apple, stored for 24 h, then washed with sterile water (control) or with sanitizers for the prescribed time. Recovered bacteria were enumerated on trypticase soy agar. Washing with water alone reduced the recoverable population by almost 2 logs from the starting population; this can be attributed to physical removal of organisms from the apple surface. No sanitizer, when used at the recommended concentration, reduced the recovered E. coli population by 5 logs under the test conditions. The most effective sanitizer, peroxyacetic acid, achieved a 5-log reduction when used at 2.1 to 14 times its recommended concentration, depending on the length of the wash time. The chlorine-phosphate buffer solution reduced the population by 5 logs when used at 3 to 15 times its recommended concentration, depending on wash time. At no concentration or wash time tested did chlorine dioxide achieve the 5-log reduction.

Inactivation of Escherichia coli O157:H7, Salmonella enterica Serotype Enteritidis, and Listeria monocytogenes on Lettuce by Hydrogen Peroxide and Lactic Acid and by Hydrogen Peroxide with Mild Heat

2002 ◽  
Vol 65 (8) ◽  
pp. 1215-1220 ◽  
Author(s):  
CHIA-MIN LIN ◽  
SARAH S. MOON ◽  
MICHAEL P. DOYLE ◽  
KAY H. McWATTERS
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Salmonella Enterica ◽  
Salmonella Enteritidis ◽  
Sensory Characteristics ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Log Reduction

Iceberg lettuce is a major component in vegetable salad and has been associated with many outbreaks of foodborne illnesses. In this study, several combinations of lactic acid and hydrogen peroxide were tested to obtain effective antibacterial activity without adverse effects on sensory characteristics. A five-strain mixture of Escherichia coli O157:H7, Salmonella enterica serotype Enteritidis, and Listeria monocytogenes was inoculated separately onto fresh-cut lettuce leaves, which were later treated with 1.5% lactic acid plus 1.5% hydrogen peroxide (H2O2) at 40°C for 15 min, 1.5% lactic acid plus 2% H2O2 at 22°C for 5 min, and 2% H2O2 at 50°C for 60 or 90 s. Control lettuce leaves were treated with deionized water under the same conditions. A 4-log reduction was obtained for lettuce treated with the combinations of lactic acid and H2O2 for E. coli O157:H7 and Salmonella Enteritidis, and a 3-log reduction was obtained for L. monocytogenes. However, the sensory characteristics of lettuce were compromised by these treatments. The treatment of lettuce leaves with 2% H2O2 at 50°C was effective not only in reducing pathogenic bacteria but also in maintaining good sensory quality for up to 15 days. A ≤4-log reduction of E. coli O157:H7 and Salmonella Enteritidis was achieved with the 2% H2O2 treatment, whereas a 3-log reduction of L. monocytogenes was obtained. There was no significant difference (P &gt; 0.05) between pathogen population reductions obtained with 2% H2O2 with 60- and 90-s exposure times. Hydrogen peroxide residue was undetectable (the minimum level of sensitivity was 2 ppm) on lettuce surfaces after the treated lettuce was rinsed with cold water and centrifuged with a salad spinner. Hence, the treatment of lettuce with 2% H2O2 at 50°C for 60 s is effective in initially reducing substantial populations of foodborne pathogens and maintaining high product quality.

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