Chlorine Inactivation of Escherichia coli O157:H7 in Water

2001 ◽  
Vol 64 (10) ◽  
pp. 1607-1609 ◽  
Author(s):  
TONG ZHAO ◽  
MICHAEL P. DOYLE ◽  
PING ZHAO ◽  
PAUL BLAKE ◽  
FONE-MAO WU
Keyword(s):  
Escherichia Coli ◽  
Reference Strain ◽  
Free Chlorine ◽  
Escherichia Coli O157 ◽  
Control Strain ◽  
Future Studies ◽  
E Coli ◽  
Sampling Times

Six human isolates of Escherichia coli O157:H7 and E. coli (ATCC 11229) were used to determine the concentrations of free chlorine and exposure times required for inactivation. Free chlorine concentrations of 0.25, 0.5, 1.0, and 2.0 ppm at 23°C were evaluated, with sampling times at 0, 0.5, 1.0, and 2.0 min. Results revealed that five of six E. coli O157:H7 isolates and the E. coli control strain were highly susceptible to chlorine, with >7 log10 CFU/ml reduction of each of these strains by 0.25 ppm free chlorine within 1 min. However, comparatively, one of the seven strains was unusually tolerant to chlorine at 23°C for 1 min, with a 4-, 5.5-, 5.8-, and >5.8-log CFU/ml reduction at free chlorine concentrations (ppm) of 0.25, 0.5, 1.0, and 2.0, respectively. Based on these studies most isolates of E. coli O157:H7 have no unusual tolerance to chlorine; however, one strain was exceptional in being recovered after 1-min of exposure of 107 CFU/ml to 2.0 ppm of free chlorine. This isolate may be a useful reference strain for future studies on chlorine tolerance of E. coli O157:H7.

PCR for the Specific Detection of an Escherichia coli O157:H7 Laboratory Control Strain

2015 ◽  
Vol 78 (9) ◽  
pp. 1738-1744 ◽  
Author(s):  
MICHAEL KNOWLES ◽  
DOMINIC LAMBERT ◽  
GEORGE HUSZCZYNSKI ◽  
MARTINE GAUTHIER ◽  
BURTON W. BLAIS
Keyword(s):  
Escherichia Coli ◽  
Pathogenic Bacteria ◽  
Control Measure ◽  
Positive Control ◽  
Food Microbiology ◽  
Escherichia Coli O157 ◽  
Control Strain ◽  
E Coli ◽  
Signature Sequences ◽  
Materials Used

Control strains of bacterial pathogens such as Escherichia coli O157:H7 are commonly processed in parallel with test samples in food microbiology laboratories as a quality control measure to assure the satisfactory performance of materials used in the analytical procedure. Before positive findings can be reported for risk management purposes, analysts must have a means of verifying that pathogenic bacteria (e.g., E. coli O157:H7) recovered from test samples are not due to inadvertent contamination with the control strain routinely handled in the laboratory environment. Here, we report on the application of an in-house bioinformatic pipeline for the identification of unique genomic signature sequences in the development of specific oligonucleotide primers enabling the identification of a common positive control strain, E. coli O157:H7 (ATCC 35150), using a simple PCR procedure.

Development of an Algorithm for Feed-Forward Chlorine Dosing of Lettuce Wash Operations and Correlation of Chlorine Profile with Escherichia coli O157:H7 Inactivation

2014 ◽  
Vol 77 (4) ◽  
pp. 558-566 ◽  
Author(s):  
BIN ZHOU ◽  
YAGUANG LUO ◽  
XIANGWU NOU ◽  
PATRICIA MILLNER
Keyword(s):  
Escherichia Coli ◽  
Reduction Potential ◽  
Free Chlorine ◽  
Organic Load ◽  
Escherichia Coli O157 ◽  
Feed Forward ◽  
E Coli ◽  
Wash Solution ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

The dynamic interactions of chlorine and organic matter during a simulated fresh-cut produce wash process and the consequences for Escherichia coli O157:H7 inactivation were investigated. An algorithm for a chlorine feed-forward dosing scheme to maintain a stable chlorine level was further developed and validated. Organic loads with chemical oxygen demand of 300 to 800 mg/liter were modeled using iceberg lettuce. Sodium hypochlorite (NaOCl) was added to the simulated wash solution incrementally. The solution pH, free and total chlorine, and oxidation-reduction potential were monitored, and chlorination breakpoint and chloramine humps determined. The results indicated that the E. coli O157:H7 inactivation curve mirrored that of the free chlorine during the chlorine replenishment process: a slight reduction in E. coli O157:H7 was observed as the combined chlorine hump was approached, while the E. coli O157:H7 cell populations declined sharply after chlorination passed the chlorine hump and decreased to below the detection limit (<0.75 most probable number per ml) after the chlorination breakpoint was reached. While the amounts of NaOCl required for reaching the chloramine humps and chlorination breakpoints depended on the organic loads, there was a linear correlation between NaOCl input and free chlorine in the wash solution once NaOCl dosing passed the chlorination breakpoint, regardless of organic load. The data obtained were further exploited to develop a NaOCl dosing algorithm for maintaining a stable chlorine concentration in the presence of an increasing organic load. The validation tests results indicated that free chlorine could be maintained at target levels using such an algorithm, while the pH and oxidation-reduction potential were also stably maintained using this system.

Comparison of Two Sampling Methods for Escherichia coli O157:H7 Detection in Feedlot Cattle

2005 ◽  
Vol 68 (8) ◽  
pp. 1724-1728 ◽  
Author(s):  
M. L. KHAITSA ◽  
M. L. BAUER ◽  
P. S. GIBBS ◽  
G. P. LARDY ◽  
D. DOETKOTT ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Sampling Methods ◽  
Feedlot Cattle ◽  
Sampling Time ◽  
Escherichia Coli O157 ◽  
Confounding Factors ◽  
Rank Tests ◽  
E Coli ◽  
Signed Rank ◽  
Sampling Times

Two sampling methods (rectoanal swabs and rectal fecal grabs) were compared for their recovery of Escherichia coli O157:H7 from feedlot cattle. Samples were collected from 144 steers four times during the finishing period by swabbing the rectoanal mucosa with cotton swabs and immediately obtaining feces from the rectum of each individual steer. The number of steers with detectable E. coli O157:H7 increased from 2 of 144 (1.4%) cattle on arrival at the feedlot to 10 of 144 (6.9%) after 1 month, 76 of 143 (52.8%) after 7 months, and 30 of 143 (20.8%) at the last sampling time before slaughter. Wilcoxon signed-rank tests indicated that the two sampling methods gave different results for sampling times 3 and 4 (P < 0.05) but not for sampling time 2 (P = 0.16). Agreement between the two sampling methods was poor (kappa < 0.2) for three of the four sampling times and moderate (kappa = 0.6) for one sampling time, an indication that in this study rectoanal swabs usually were less sensitive than rectal fecal grabs for detection of E. coli O157:H7 in cattle. Overall, the herd of origin was not significantly associated with E. coli O157:H7 results, but the weight of the steers was. Further investigation is needed to determine the effects of potential confounding factors (e.g., size and type of swab, consistency of feces, site sampled, and swabbing technique) that might influence the sensitivity of swabs in recovering E. coli O157:H7 from the rectoanal mucosa of cattle.

Two Generally Recognized as Safe Surfactants plus Acidulants Inactivate Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in Suspension or on Dip-Inoculated Grape Tomatoes

2020 ◽  
Vol 83 (4) ◽  
pp. 637-643
Author(s):  
JOSHUA B. GURTLER
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Bovine Serum ◽  
Fresh Produce ◽  
Free Chlorine ◽  
Sodium Dodecylbenzene Sulfonate ◽  
Escherichia Coli O157 ◽  
E Coli

ABSTRACT Contamination of fresh produce with the foodborne pathogens Salmonella enterica, Listeria monocytogenes, and Escherichia coli O157:H7 continues to be problematic, resulting in outbreaks of foodborne illness and costly corporate recalls. Various individual concentrations of citric or lactic acids (0.35 to 0.61%) or isopropyl citrate (0.16 to 0.54%) combined with two generally recognized as safe surfactants, 0.025% sodium-2-ethyl-hexyl sulfate and 0.025% sodium dodecylbenzene-sulfonate, were tested against these three pathogens in suspension and when inoculated and dried on the surface of grape tomatoes. The efficacy of sodium hypochlorite (NaClO; at 46 ppm) was also evaluated under dirty and clean conditions in suspension after addition of 0.3 or 0.03% bovine serum albumin, respectively, as an organic load. NaClO (46 ppm) inactivated the three pathogens in suspension by <0.76 log CFU/mL after 5 min in the presence of 0.3% bovine serum albumin, whereas 9 and 15 ppm of free chlorine inactivated the pathogens by 0.64 and 2.77 log CFU/mL, respectively, after 5 min under clean conditions. Isopropyl citrate (0.16% acidulant) plus 0.05% total concentration of the two surfactants inactivated the pathogens in suspension by up to 7.0 log CFU/mL within 2 min. When applied to grape tomatoes for 2 min, 0.54% isopropyl citrate plus 0.025% concentrations of each of the two surfactants reduced Salmonella, E. coli O157:H7, and L. monocytogenes by as much as ca. 5.47, 4.89, and 4.19 log CFU/g, respectively. These reductions were significantly greater than those achieved with 49 ppm of free chlorine. Citric acid and lactic acid plus surfactant washes achieved greater inactivation than water-only washes, reducing Salmonella, E. coli O157:H7, and L. monocytogenes on tomatoes by up to 4.90, 4.37, and 3.98 log CFU/g, respectively. These results suggest that these combinations of acidulants and surfactants may be an effective tool for preventing cross-contamination during the washing of grape tomatoes, for reducing pathogens on the fruit itself, and as an alternative to chlorine for washing fresh produce. HIGHLIGHTS

Survival of Escherichia coli O157:H7 in Ground-Beef Patties during Storage at 2, −2, 15 and then −2°C, and −20°C†

1999 ◽  
Vol 62 (11) ◽  
pp. 1243-1247 ◽  
Author(s):  
SUSAN E. ANSAY ◽  
KIM A. DARLING ◽  
CHARLES W. KASPAR
Keyword(s):  
Escherichia Coli ◽  
Frozen Storage ◽  
Ground Beef ◽  
Plate Count ◽  
Escherichia Coli O157 ◽  
Control Strain ◽  
Single Strain ◽  
E Coli ◽  
Beef Patties ◽  
Significant Difference

The survival of Escherichia coli O157:H7 and of a nonpathogenic control strain of E. coli was monitored in raw ground beef that was stored at 2°C for 4 weeks, −2°C for 4 weeks, 15°C for 4 h and then −2°C for 4 weeks, and −20°C. Irradiated ground beef was inoculated with one E. coli control strain or with a four-strain cocktail of E. coli O157:H7 (ca. 105 CFU/g), formed into patties (30 to 45 g), and stored at the appropriate temperature. The numbers of the E. coli control strain decreased by 1.4 log10 CFU/g, and pathogen numbers declined 1.9 log10 CFU/g when patties were stored for 4 weeks at 2°C. When patties were stored at −2°C for 4 weeks, the numbers of the E. coli control strain and the serotype O157:H7 strains decreased 2.8 and 1.5 log10 CFU/g, respectively. Patties stored at 15°C for 4 h prior to storage at −2°C for 4 weeks resulted in 1.6 and 2.7 log10–CFU/g reduction in the numbers of E. coli and E. coli O157:H7, respectively. Storage of retail ground beef at 15°C for 4 h (tempering) did not result in increased numbers of colony forming units per gram, as determined with violet red bile, MRS lactobacilli, and plate-count agars. Frozen storage (−20°C) of ground-beef patties that had been inoculated with a single strain of E. coli resulted in approximately a 1 to 2 log10–CFU/g reduction in the numbers of the control strain and individual serotype O157:H7 strains after 1 year. There was no significant difference between the survival of the control strain and the O157:H7 strains, nor was there a difference between O157:H7 strains. These data demonstrate that tempering of ground-beef patties prior to low-temperature storage accelerated the decline in the numbers of E. coli O157:H7.

Determination of Free Chlorine Concentrations Needed To Prevent Escherichia coli O157:H7 Cross-Contamination during Fresh-Cut Produce Wash†

2011 ◽  
Vol 74 (3) ◽  
pp. 352-358 ◽  
Author(s):  
YAGUANG LUO ◽  
XIANGWU NOU ◽  
YANG YANG ◽  
ISABEL ALEGRE ◽  
ELLEN TURNER ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Free Chlorine ◽  
Chlorine Concentration ◽  
Wash Water ◽  
Escherichia Coli O157 ◽  
Cross Contamination ◽  
E Coli ◽  
Wash Solution ◽  
Fresh Cut ◽  
Experimental Trials

This study was conducted to investigate the effect of free chlorine concentrations in wash water on Escherichia coli O157:H7 reduction, survival, and transference during washing of fresh-cut lettuce. The effectiveness of rewashing for inactivation of E. coli O157:H7 on newly cross-contaminated produce previously washed with solutions containing an insufficient amount of chlorine also was assessed. Results indicate that solutions containing a minimum of 0.5 mg/liter free chlorine were effective for inactivating E. coli O157:H7 in suspension to below the detection level. However, the presence of 1 mg/liter free chlorine in the wash solution before washing was insufficient to prevent E. coli O157:H7 survival and transfer during washing because the introduction of cut lettuce to the wash system quickly depleted the free chlorine. Although no E. coli O157:H7 was detected in the wash solution containing 5 mg/liter free chlorine before washing a mix of inoculated and uninoculated lettuce, low numbers of E. coli O157:H7 cells were detected on uninoculated lettuce in four of the seven experimental trials. When the prewash free chlorine concentration was increased to 10 mg/liter or greater, no E. coli O157:H7 transfer was detected. Furthermore, although rewashing newly cross-contaminated lettuce in 50 mg/liter free chlorine for 30 s significantly reduced (P = 0.002) the E. coli O157:H7 populations, it failed to eliminate E. coli O157:H7 on lettuce. This finding suggests that rewashing is not an effective way to correct for process failure, and maintaining a sufficient free chlorine concentration in the wash solution is critical for preventing pathogen cross-contamination.

Escherichia coli O157: H7 Acid Tolerance and Survival in Apple Cider

1994 ◽  
Vol 57 (6) ◽  
pp. 460-464 ◽  
Author(s):  
LESLIE GARLAND MILLER ◽  
CHARLES W. KASPAR
Keyword(s):  
Escherichia Coli ◽  
Sodium Benzoate ◽  
Acid Tolerance ◽  
Potassium Sorbate ◽  
Escherichia Coli O157 ◽  
Control Strain ◽  
High Ph ◽  
Apple Cider ◽  
E Coli ◽  
Log Reduction

The survival of two Escherichia coli O157:H7 (ATCC 43889 and 43895) and a control strain E. coli was compared in apple cider and in Trypticase soy broth (TSB) adjusted to low and high pH. The O157:H7 strains were detectable in apple cider after 14 to 21 days at 4°C, whereas the control strain could not be detected (> 4-log reduction) after 5 to 7 days. During the first 14 days of storage at 4°C, the levels of strain 43889 decreased by ~3 logs, whereas levels of strain 43895 were unchanged. Survival of O157:H7 strains and the control strain were unaffected by the presence of potassium sorbate or sodium benzoate, except in one instance. Sodium benzoate caused a decrease of 57% in strain 43895 after 21 days, but ~104 CFU/ml still remained. In TSB adjusted to pH 2, 3, 4, 11 or 12, strain 43895 was again the more resistant of the O157:H7 strains, both of which were more durable than the control strain. The O157:H7 strains (especially strain 43895) withstood pH 2 with a minimal drop in CPU after 24 h, whereas no viable organisms were detectable after this time at pH 12. At these extremes of pH, survival was generally greater at 4°C than at 25°C. Despite differences between strains, these results show that E. coli O157:H7 is exceptionally tolerant of acid pH.

scholarly journals Cross-reacting surface proteins between different Escherichia coli O157:H7 strains and their immune responses in animal models

2019 ◽  
Vol 36 (1) ◽  
pp. 11-15
Author(s):  
Ashikun Nabi ◽  
Fatema Moni Chowdhury ◽  
Zeenat Jahan ◽  
Md Murshed Hasan Sarkar ◽  
Fazle Rabbi ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Reference Strain ◽  
Protective Antigen ◽  
Surface Protein ◽  
Immunoblot Analysis ◽  
Surface Proteins ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Challenge Experiment ◽  
Different Strains

Surface proteins of Escherichia coli O157:H7, those that are prominent in antigen-antibody reactions among different strains, were found to provide protection against E. coli O157 challenge in mice. Three strains such as E. coli O157:H7 NCTC reference strain and two other environmentally isolated strains have been used in this study. New Zealand rabbits were immunized with surface proteins of NCTC reference strain and immunoblot analysis was performed against the surface proteins of all three strains. Immunoblot analysis revealed that a 94 kDa surface protein of E. coli O157:H7 could be the possible candidate for the protective activity experiment. Group of mice receiving the 94 kDa surface protein through both intraperitoneal and intranasal routes survived the challenge experiment. Whereas, all the control mice died within a couple of days. Mice challenge experiment clearly demonstrated the strong potential of the 94 kDa protein in the immunized mice. The data of this study provide us with a basis for further characterization of 94 kDa surface protein of E. coli O157:H7 as a protective antigen. Bangladesh J Microbiol, Volume 36 Number 1 June 2019, pp 11-15

Reduction of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes with Electrolyzed Oxidizing Water on Inoculated Hass Avocados (Persea americana var. Hass)

2011 ◽  
Vol 74 (9) ◽  
pp. 1552-1557 ◽  
Author(s):  
O. RODRÍGUEZ-GARCIA ◽  
V. M. GONZÁLEZ-ROMERO ◽  
E. FERNÁNDEZ-ESCARTÍN
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Salmonella Enterica ◽  
Tap Water ◽  
Bactericidal Effect ◽  
Persea Americana ◽  
Free Chlorine ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Pathogen Populations

This study was intended to evaluate the bactericidal effect of electrolyzed oxidizing water (EOW) and chlorinated water on populations of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes inoculated on avocados (Persea americana var. Hass). In the first experiment, inoculated avocados were treated with a water wash applied by spraying tap water containing 1 mg/liter free chlorine for 15 s (WW); WW treatment and then spraying sodium hypochlorite in water containing 75 mg/liter free chlorine for 15 s (Cl75); WW treatment and then spraying alkaline EOW for 30 s (AkEW) and then spraying acid EOW (AcEW) for 15 s; and spraying AkEW and then AcEW. In another experiment, the inoculated avocados were treated by spraying AkEW and then AcEW for 15, 30, 60, or 90 s. All three pathogen populations were lowered between 3.6 and 3.8 log cycles after WW treatment. The application of Cl75 did not produce any further reduction in counts, whereas AkEW and then AcEW treatment resulted in significantly lower bacterial counts for L. monocytogenes and E. coli O157:H7 but not for Salmonella. Treatments with AkEW and then AcEW produced a significant decrease in L. monocytogenes, Salmonella, and E. coli O157:H7 populations, with estimated log reductions of 3.9 to 5.2, 5.1 to 5.9, and 4.2 to 4.9 log CFU/cm2, respectively. Spraying AcEW for more than 15 s did not produce any further decrease in counts of Salmonella or E. coli O157:H7, whereas L. monocytogenes counts were significantly lower after spraying AcEW for 60 s. Applying AkEW and then AcEW for 15 or 30 s seems to be an effective alternative to reduce bacterial pathogens on avocado surfaces.

Effect of Water Hardness on Efficacy of Sodium Hypochlorite Inactivation of Escherichia coli O157:H7 in Water

2017 ◽  
Vol 80 (3) ◽  
pp. 497-501 ◽  
Author(s):  
Sara Swanson ◽  
Tong-Jen Fu
Keyword(s):  
Escherichia Coli ◽  
Sodium Hypochlorite ◽  
Water Hardness ◽  
Hard Water ◽  
Free Chlorine ◽  
Total Hardness ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Effect Of Water ◽  
The Impact

ABSTRACT This study examined how the hardness of water affected the efficacy of sodium hypochlorite in inactivating Escherichia coli O157:H7 in water. Water was prepared at different degrees of total hardness (0, 50, 100, 200, 500, 1,000, 2,000, and 5,000 mg/liter CaCO3). Inactivation was assessed at different levels of free chlorine (0, 0.2, 0.5, and 1.0 ppm) at 2 to 4°C and pH 6.5. Thirty milliliters of chlorinated water was inoculated with 6 log CFU/ml of E. coli O157:H7 and allowed to mix for 3, 10, 20, or 30 s. In the absence of sodium hypochlorite, no reduction in counts of E. coli O157:H7 was observed regardless of the degree of water hardness. However, in the presence of hard water, under certain chlorine concentrations and exposure times, the reduction of E. coli O157:H7 in chlorinated hard water was significantly less than the reduction observed in chlorinated deionized water. For example, after exposure to 0.5 ppm of free chlorine for 10 s, E. coli O157:H7 counts were reduced by 4.8 ± 1.4, 2.0 ± 1.3, 1.6 ± 0.7, 0.5 ± 0.7, and 0.0 ± 0.1 log CFU/ml in water containing 0, 100, 1,000, 2,000, and 5,000 mg/liter CaCO3, respectively. With the exception of 5,000 mg/liter CaCO3, the effect of water hardness was no longer visible after 20 s of exposure to 0.5 ppm of free chlorine. Also, hard water significantly lowered the efficacy of sodium hypochlorite at 3 s of exposure to 1.0 ppm of free chlorine. But after 20 s of exposure to 1.0 ppm of free chlorine, the impact of water hardness was no longer observed. This study demonstrated that water hardness can affect the germicidal efficacy of sodium hypochlorite, and such an impact may or may not be apparent depending on the condition of the solution and the treatment time at which the observation is made. Under the conditions typically seen in commercial produce washing operations, the impact of water hardness on chlorine efficacy is likely to be insignificant compared with that of organic load.

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