Application of bacteriophages EP75 and EP335 efficiently reduces viable cell counts of Escherichia coli O157 on beef and vegetables

An efficacy test of GC-100X, a noncorrosive alkaline ionic fluid (pH 12) composed of free radicals and supplemented with xylitol, was carried out against six major foodborne pathogens—Staphylococcus aureus FRI 913, Salmonella enterica serovar Enteritidis ATCC 13076, S. enterica serovar Typhimurium DT104 Korean isolate, Vibrio parahaemolyticus ATCC 17803, Escherichia coli O157:H7 ATCC 43894, and Pseudomonas aeruginosa KCTC 1637—at three different temperatures (4, 25, and 36°C) with or without organic load (2% yeast extract). Results revealed a more than 4-log10 (CFU/ml) reduction (1.0 × 104 CFU/ml reduction) against all pathogens reacted at 37°C for 3 h in the absence of organic material. GC-100X solution diluted with an equal volume of distilled or standard hard water (300 ppm CaCO3) showed effective bactericidal activity, particularly against gram-negative bacteria. Washing efficacy of GC-100X solution was compared against E. coli O157:H7 on cherry tomato surfaces with those of a commercially used detergent and chlorine water (100 ppm). Viable cell counts of E. coli O157:H7 that had penetrated to the cores of tomatoes after sanitizing treatment revealed that GC-100X stock and its 5% diluted solutions had similar washing effects to 100-ppm chlorine water and were more effective than the other kitchen detergent. These results indicate that GC-100X has good bactericidal and sanitizing activities and is useful as a new sanitizer for food safety and kitchen hygiene.

Download Full-text

The dynamic balance of import and export of zinc in Escherichia coli suggests a heterogeneous population response to stress

Journal of The Royal Society Interface ◽

10.1098/rsif.2015.0069 ◽

2015 ◽

Vol 12 (106) ◽

pp. 20150069 ◽

Cited By ~ 14

Author(s):

Hiroki Takahashi ◽

Taku Oshima ◽

Jon L. Hobman ◽

Neil Doherty ◽

Selina R. Clayton ◽

...

Keyword(s):

Escherichia Coli ◽

Zinc Concentration ◽

Systems Approach ◽

Model Simulation ◽

Dynamic Balance ◽

Model Fitting ◽

Viable Cell ◽

Population Heterogeneity ◽

Cell Counts ◽

Import And Export

Zinc is essential for life, but toxic in excess. Thus all cells must control their internal zinc concentration. We used a systems approach, alternating rounds of experiments and models, to further elucidate the zinc control systems in Escherichia coli . We measured the response to zinc of the main specific zinc import and export systems in the wild-type, and a series of deletion mutant strains. We interpreted these data with a detailed mathematical model and Bayesian model fitting routines. There are three key findings: first, that alternate, non-inducible importers and exporters are important. Second, that an internal zinc reservoir is essential for maintaining the internal zinc concentration. Third, our data fitting led us to propose that the cells mount a heterogeneous response to zinc: some respond effectively, while others die or stop growing. In a further round of experiments, we demonstrated lower viable cell counts in the mutant strain tested exposed to excess zinc, consistent with this hypothesis. A stochastic model simulation demonstrated considerable fluctuations in the cellular levels of the ZntA exporter protein, reinforcing this proposal. We hypothesize that maintaining population heterogeneity could be a bet-hedging response allowing a population of cells to survive in varied and fluctuating environments.

Download Full-text

Performance of Some Heat-Sensitive Differential Agars Prepared and Melted by Microwave Energy1

Journal of Food Protection ◽

10.4315/0362-028x-51.7.577 ◽

1988 ◽

Vol 51 (7) ◽

pp. 577-578 ◽

Cited By ~ 1

Author(s):

C. LIANG ◽

D. Y. C. FUNG

Keyword(s):

Escherichia Coli ◽

Cell Count ◽

Viable Cell ◽

Microwave Energy ◽

Microwave Oven ◽

Viable Cell Count ◽

Streptococcus Faecalis ◽

Cell Counts ◽

Significant Difference ◽

Conventional Boiling

The viable cell count performance of some heat-sensitive differential agars prepared and remelted by microwave energy was evaluated for Salmonella choleraesui, Streptococcus faecalis and Escherichia coli. The conventional boiling method was used for comparison. No significant difference was found between the microwave oven processed agar and the conventional-boiling processed agar in viable cell counts of the target bacteria. Heating and reheating of violet red bile agar, bismuth sulfite agar, and KF Streptococcus agar by both methods did not change agar performance. However, remelting of desoxycholate citrate agar by both methods resulted in a substantial lowering of viable cell counts.

Download Full-text

Antibacterial Effect of Water-Soluble Arrowroot (Puerariae radix) Tea Extracts on Foodborne Pathogens in Ground Beef and Mushroom Soup

Journal of Food Protection ◽

10.4315/0362-028x-67.9.1953 ◽

2004 ◽

Vol 67 (9) ◽

pp. 1953-1956 ◽

Cited By ~ 23

Author(s):

S. KIM ◽

D. Y. C. FUNG

Keyword(s):

Foodborne Pathogens ◽

Salmonella Enteritidis ◽

Ground Beef ◽

Viable Cell ◽

Water Soluble ◽

Escherichia Coli O157 ◽

E Coli ◽

Cell Counts ◽

Tea Extract ◽

And Staphylococcus Aureus

Antimicrobial activity of water-soluble arrowroot tea extract was evaluated against Escherichia coli O157:H7, Salmonella enterica Serotype Enteritidis, Listeria monocytogenes, and Staphylococcus aureus in ground beef and mushroom soup. The concentrations of arrowroot tea used were 0, 3, and 6% (wt/wt) for ground beef and 0, 1, 5, and 10% (wt/vol) for mushroom soup. Samples without tea extract were considered controls. Each sample was stored for 0, 1, 3, 5, and 7 days at 7°C for ground beef and for 0, 1, 3, and 5 days at 35°C for mushroom soup. On each sampling time, proper dilutions were spread plated on each pathogen-specific agar. Viable cell counts of each pathogen were performed after incubation at 35°C for 24 to 48 h. For ground beef, Salmonella Enteritidis and L. monocytogenes were slightly suppressed by approximately 1.5 log, compared with the control, on day 7 at 3 and 6% arrowroot tea treatment. For mushroom soup, all test pathogens were suppressed by 6.5, 4.7, 3.4, and 4.3 log at 5% and 6.0, 4.7, 5.0, and 4.3 log at 10% against E. coli O157:H7, Salmonella Enteritidis, L. monocytogenes, and S. aureus, respectively, compared with the control on day 5. Mushroom soup with 1% arrowroot tea also showed 2.3- and 2.7-log growth suppression of Salmonella Enteritidis and S. aureus, respectively, compared with the control on day 5. This study showed that the use of arrowroot tea would effectively inhibit the microbial growth of both gram-negative and gram-positive foodborne pathogens in various foods, especially liquid foods.

Download Full-text

An Investigation of Escherichia coli O157 Contamination of Cattle during Slaughter at an Abattoir

Journal of Food Protection ◽

10.4315/0362-028x-68.3.451 ◽

2005 ◽

Vol 68 (3) ◽

pp. 451-457 ◽

Cited By ~ 46

Author(s):

NARELLE FEGAN ◽

GLEN HIGGS ◽

PAUL VANDERLINDE ◽

PATRICIA DESMARCHELIER

Keyword(s):

Escherichia Coli ◽

Oral Cavity ◽

Immunomagnetic Separation ◽

Most Probable Number ◽

Escherichia Coli O157 ◽

Probable Number ◽

Fecal Samples ◽

E Coli ◽

Cell Counts ◽

Carcass Contamination

The extent of contamination with Escherichia coli O157 was determined for 100 cattle during slaughter. Samples from 25 consecutively slaughtered cattle from four unrelated groups were collected from the oral cavity, hide, rumen, feces after evisceration, and pre- and postchill carcass. Ten random fecal samples were collected from the pen where each group of animals was held at the abattoir. E. coli O157 was detected using automated immunomagnetic separation (AIMS), and cell counts were determined using a combination of most probable number (MPN) and AIMS. E. coli O157 was isolated from 87 (14%) of the 606 samples collected, including 24% of 99 oral cavity samples, 44% of 100 hides, 10% of 68 fecal samples collected postevisceration, 6% of 100 prechill carcass swabs, and 15% of 40 fecal samples collected from holding pens. E. coli O157 was not isolated from rumen or postchill carcass samples. E. coli O157 was isolated from at least one sample from each group of cattle tested, and the prevalence in different groups ranged from less than 1 to 41%. The numbers of E. coli O157 differed among the animals groups. The group which contained the highest fecal (7.5 × 105 MPN/g) and hide (22 MPN/cm2) counts in any individual animal was the only group in which E. coli O157 was isolated from carcasses, suggesting a link between the numbers of E. coli O157 present and the risk of carcass contamination. Processing practices at this abattoir were adequate for minimizing contamination of carcasses, even when animals were heavily contaminated with E. coli O157.

Download Full-text

Isolation and Purification of Colicin ECL 12, a Bacteriocin That Inhibits Strains of Escherichia coli O157:H7†

Journal of Food Protection ◽

10.4315/0362-028x-60.12.1520 ◽

1997 ◽

Vol 60 (12) ◽

pp. 1520-1528 ◽

Cited By ~ 5

Author(s):

WANDA J. LYON ◽

DENNIS G. OLSON

Keyword(s):

Escherichia Coli ◽

Proteolytic Enzymes ◽

Polyacrylamide Gel Electrophoresis ◽

Sodium Dodecyl ◽

Viable Cell ◽

Exchange Chromatography ◽

Isolation And Purification ◽

E Coli ◽

Log Reduction ◽

Cell Counts

A swine fecal isolate, identified as Escherichia coli ECL12, was found to produce an antimicrobial substance designated as colicin ECL12. Colicin ECL12 was inhibitory against 20 strains of E. coli O157:H7 previously isolated from both human and bovine feces. Identification of the producer strain was determined phenotypically by biochemical and morphological tests. Colicin ECL12 was sensitive to several proteolytic enzymes. Adsorption of colicin ECL12 to sensitive cells of E. coli O157:H7 was bactericidal, resulting in a 2 log reduction in viable cell counts. Colicin ECL12 was purified from strain ECL12 by cell extraction and ion-exchange chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of colicin ECL12 resolved a single protein with a molecular weight of approximately 65,000.

Download Full-text

Validation of a Noninvasive, Real-Time Imaging Technology Using Bioluminescent Escherichia coli in the Neutropenic Mouse Thigh Model of Infection

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.45.1.129-137.2001 ◽

2001 ◽

Vol 45 (1) ◽

pp. 129-137 ◽

Cited By ~ 106

Author(s):

H. L. Rocchetta ◽

C. J. Boylan ◽

J. W. Foley ◽

P. W. Iversen ◽

D. L. LeTourneau ◽

...

Keyword(s):

Escherichia Coli ◽

Real Time ◽

Antimicrobial Agents ◽

Viable Cell ◽

Multicopy Plasmid ◽

In Vivo Evaluation ◽

Therapeutic Success ◽

Cell Counts

ABSTRACT A noninvasive, real-time detection technology was validated for qualitative and quantitative antimicrobial treatment applications. Thelux gene cluster of Photorhabdus luminescenswas introduced into an Escherichia coli clinical isolate, EC14, on a multicopy plasmid. This bioluminescent reporter bacterium was used to study antimicrobial effects in vitro and in vivo, using the neutropenic-mouse thigh model of infection. Bioluminescence was monitored and measured in vitro and in vivo with an intensified charge-coupled device (ICCD) camera system, and these results were compared to viable-cell determinations made using conventional plate counting methods. Statistical analysis demonstrated that in the presence or absence of antimicrobial agents (ceftazidime, tetracycline, or ciprofloxacin), a strong correlation existed between bioluminescence levels and viable cell counts in vitro and in vivo. Evaluation of antimicrobial agents in vivo could be reliably performed with either method, as each was a sound indicator of therapeutic success. Dose-dependent responses could also be detected in the neutropenic-mouse thigh model by using either bioluminescence or viable-cell counts as a marker. In addition, the ICCD technology was examined for the benefits of repeatedly monitoring the same animal during treatment studies. The ability to repeatedly measure the same animals reduced variability within the treatment experiments and allowed equal or greater confidence in determining treatment efficacy. This technology could reduce the number of animals used during such studies and has applications for the evaluation of test compounds during drug discovery.

Download Full-text

Prewashing with Acidified Sodium Chlorite Reduces Pathogenic Bacteria in Lightly Fermented Chinese Cabbage

Journal of Food Protection ◽

10.4315/0362-028x-68.5.999 ◽

2005 ◽

Vol 68 (5) ◽

pp. 999-1004 ◽

Cited By ~ 17

Author(s):

YASUHIRO INATSU ◽

YUTAKA MAEDA ◽

M. L. BARI ◽

SUSUMU KAWASAKI ◽

SHINICHI KAWAMOTO

Keyword(s):

Chinese Cabbage ◽

Salmonella Enteritidis ◽

Pathogenic Bacteria ◽

Control Experiment ◽

Viable Cell ◽

Sodium Chlorite ◽

Distilled Water ◽

Escherichia Coli O157 ◽

Cell Counts ◽

Natural Microflora

Efficacy of prewashing with acidified sodium chlorite (ASC) for the sanitation of lightly fermented Chinese cabbage was evaluated. The population of the natural microflora on the cabbage leaves was reduced about 2.0 log CFU/g just after washing with ASC, a significant reduction compared with the control distilled water wash (P ≤ 0.05). In the control experiment, viable aerobic bacteria increased gradually when incubated at 10°C; however, ASC-washed cabbage maintained a lower microbial concentration. The treatment of Chinese cabbage with ASC reduced the population of artificially inoculated Escherichia coli O157:H7, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes by 2.4 log CFU/g. The sanitation efficacy of ASC was 1.6 log CFU/g higher than that of distilled water washing. The viable cell counts of all pathogenic bacteria tested remained constant during 8 days of storage at 10°C for both washing treatments, with the exception of L. monocytogenes, whose viable cell counts increased gradually with time for both treatments. No significant differences in color, odor, taste, and texture in raw leaves were observed after the ASC wash compared with after the distilled water wash. These results indicate that prewashing with ASC could control bacterial growth in lightly fermented Chinese cabbage without changing the product quality.

Download Full-text

Persister cells mediate tolerance to metal oxyanions in Escherichia coli

Microbiology ◽

10.1099/mic.0.27794-0 ◽

2005 ◽

Vol 151 (10) ◽

pp. 3181-3195 ◽

Cited By ~ 83

Author(s):

Joe J. Harrison ◽

Howard Ceri ◽

Nicole J. Roper ◽

Erin A. Badry ◽

Kimberley M. Sproule ◽

...

Keyword(s):

Escherichia Coli ◽

Viable Cell ◽

Small Population ◽

Water Soluble ◽

Bacterial Cells ◽

Persister Cells ◽

Term Survival ◽

E Coli ◽

Cell Counts ◽

High Concentrations

Bacterial cultures produce subpopulations of cells termed ‘persisters’, reputedly known for high tolerance to killing by antibiotics. Ecologically, antibiotics produced by competing microflora are only one potential stress encountered by bacteria. Another pressure in the environment is toxic metals that are distributed ubiquitously by human pollution, volcanic activity and the weathering of minerals. This study evaluated the time- and concentration-dependent killing of Escherichia coli planktonic and biofilm cultures by the water-soluble metal(loid) oxyanions chromate (), arsenate (), arsenite (), selenite (), tellurate () and tellurite (). Correlative to previous reports in the literature, control antibiotic assays indicated that a small proportion of E. coli biofilm populations remained recalcitrant to killing by antibiotics (even with 24 h exposure). In contrast, metal oxyanions presented a slow, bactericidal action that eradicated biofilms. When exposed for 2 h, biofilms were up to 310 times more tolerant to killing by metal oxyanions than corresponding planktonic cultures. However, by 24 h, planktonic cells and biofilms were eradicated at approximately the same concentration in all instances. Coloured complexes of metals and chelators could not be generated in biofilms exposed to or , suggesting that the extracellular polymeric matrix of E. coli may have a low binding affinity for metal oxyanions. Viable cell counts at 2 and 24 h exposure revealed that, at high concentrations, all of the metal oxyanions had killed 99 % (or a greater proportion) of the bacterial cells in biofilm populations. It is suggested here that the short-term survival of <1 % of the bacterial population corresponds well with the hypothesis that a small population of persister cells may be responsible for the time-dependent tolerance of E. coli biofilms to high concentrations of metal oxyanions.

Download Full-text

Combined Effect of Water Activity and pH on the Inhibition of Escherichia coli by Nisin

Journal of Food Protection ◽

10.4315/0362-028x-64.10.1510 ◽

2001 ◽

Vol 64 (10) ◽

pp. 1510-1514 ◽

Cited By ~ 9

Author(s):

PATRICIA CERRUTTI ◽

MAURICIO R. TEREBIZNIK ◽

MARTA SEGOVIA de HUERGO ◽

ROSA JAGUS ◽

ANA M. R. PILOSOF

Keyword(s):

Escherichia Coli ◽

Water Activity ◽

Viable Cell ◽

Stress Factors ◽

Doehlert Design ◽

Survival Fraction ◽

E Coli ◽

Cell Counts ◽

Maximum Inhibition ◽

Influence Of Ph

The Doehlert design and surface response methodology were used to study the influence of pH and water activity (aw) on Escherichia coli inhibition by nisin. Combining stress factors at levels where they are not inhibitory by themselves, a reduction of E. coli survival fraction can be achieved with lower nisin doses than in a single nisin treatment. For all the pH values assayed, a synergistic effect of aw and nisin concentration was detected, and the isoresponse lines showed the existence of an area of maximum inhibition. Factors that reduced viable cell counts by 4 to 5 log cycles were 1,000 to 1,400 IU of nisin per ml at pH 5.5 to 6.5 and a water activity of 0.97 and 0.98. The addition of different ionic and nonionic solutes to control aw suggested that the effect of aw in the inhibitory action of nisin on E. coli cells was not solute-specific. The use of the Doehlert experimental design was effective to determine the optimal combination of stress factors, as well as to point out the most important variables that affected E. coli inhibition.

Download Full-text