scholarly journals Inactivation of particle-associated Escherichia coli with chlorine dioxide

2016 ◽  
Vol 17 (1) ◽  
pp. 151-160 ◽  
Author(s):  
Tao Lin ◽  
Bingwei Hou ◽  
Zhe Wang ◽  
Wei Chen
Keyword(s):  
Escherichia Coli ◽  
Chlorine Dioxide ◽  
Inactivation Rate ◽  
Inactivation Kinetics ◽  
Strong Temperature Dependence ◽  
E Coli ◽  
Inactivation Rate Constant ◽  
Effects Of Ph ◽  
Inactivation Efficiency ◽  
Kinetics Of

In this paper, the inactivation of both free Escherichia coli (FE) and particle-associated E. coli (PAE) with chlorine dioxide (ClO2) were investigated using granular activated carbon effluent water samples. The inactivation rate of FE was higher than that of PAE and the reactivation ratio of PAE was higher than that of FE, indicating the threat of particle-associated bacteria. Response surface methodology (RSM) was applied to determine the factors influencing the disinfection efficiency of ClO2 in inactivating PAE. The experimental results indicated that particle concentration was a principal factor influencing the PAE inactivation efficiency, presenting a negative correlation, while exposure time and ClO2 dosage revealed a positive correlation. The inactivation kinetics of PAE using ClO2 was also investigated and the results demonstrated that PAE inactivation with ClO2 fitted the Chick–Watson kinetic model. The inactivation rate constants of PAE were found to follow the Arrhenius expression with an activation energy of 107.5 kJ/mol, indicating a relatively strong temperature dependence. However, there are minor effects of pH and initial ClO2 dosage on PAE inactivation rate constant.

Inactivation of Escherichia coli by Ultrasound Combined with Nisin

2018 ◽  
Vol 81 (6) ◽  
pp. 993-1000 ◽  
Author(s):  
ZUWEN WANG ◽  
XIUFANG BI ◽  
RUI XIANG ◽  
LIYI CHEN ◽  
XIAOPING FENG ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Synergistic Effect ◽  
Linear Models ◽  
Treatment Time ◽  
Nutrient Broth ◽  
Inactivation Kinetics ◽  
Growth Phases ◽  
E Coli ◽  
Kinetics Of ◽  
Inactivation Effect

ABSTRACT The aim of this study was to investigate the inactivation of nonpathogenic Escherichia coli in nutrient broth and milk through the use of either ultrasound (US) alone or US combined with nisin (US + nisin) treatments. The E. coli cells were treated at 0 to 55°C, 242.04 to 968.16 W/cm2 for 0 to 15 min. The results showed that the inactivation of E. coli by US and US + nisin increased when the temperature, US power density, and treatment time were increased. The inactivation kinetics of E. coli in nutrient broth by US and US + nisin both conformed to linear models. The largest reductions of 2.89 and 2.93 log cycles by US and US + nisin, respectively, were achieved at 968.16 W/cm2 and at 25°C for 15 min. The suspension media of the E. coli cells influenced the inactivation effect of US, while the growth phases of E. coli cells did not affect their resistance to US. Under all experiment conditions of this study, the differences between US and US + nisin in their respective inactivation effects on E. coli were not obvious. The results suggested that nisin had either no effect at all or a weak synergistic effect with US and that the E. coli cells were inactivated mainly by US, thus indicating that the inactivation of E. coli by US is an “all or nothing” event.

Viability of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in Yellow Fat Spreads as Affected by Storage Temperature

2003 ◽  
Vol 66 (4) ◽  
pp. 549-558 ◽  
Author(s):  
SARAH L. HOLLIDAY ◽  
LARRY R. BEUCHAT
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Storage Temperature ◽  
Salt Content ◽  
Inactivation Kinetics ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Inhibition Of Growth ◽  
Time Required ◽  
Kinetics Of

A study was conducted to characterize the survival and inactivation kinetics of a five-serotype mixture of Salmonella (6.23 to 6.55 log10 CFU per 3.5-ml or 4-g sample), a five-strain mixture of Escherichia coli O157:H7 (5.36 to 6.14 log10 CFU per 3.5-ml or 4-g sample), and a six-strain mixture of Listeria monocytogenes (5.91 to 6.18 log10 CFU per 3.5-ml or 4-g sample) inoculated into seven yellow fat spreads (one margarine, one butter-margarine blend, and five dairy and nondairy spreads and toppings) after formulation and processing and stored at 4.4, 10, and 21°C for up to 94 days. Neither Salmonella nor E. coli O157:H7 grew in any of the test products. The time required for the elimination of each pathogen depended on the product and the storage temperature. Death was more rapid at 21°C than at 4.4 or 10°C. Depending on the product, the time required for the elimination of viable cells at 21°C ranged from 5 to 7 days to >94 days for Salmonella, from 3 to 5 days to 28 to 42 days for E. coli O157:H7, and from 10 to 14 days to >94 days for L. monocytogenes. Death was most rapid in a water-continuous spray product (pH 3.66, 4.12% salt) and least rapid in a butter-margarine blend (pH 6.66, 1.88% salt). E. coli O157:H7 died more rapidly than did Salmonella or L. monocytogenes regardless of storage temperature. Salmonella survived longer in high-fat (≥61%) products than in products with lower fat contents. The inhibition of growth is attributed to factors such as acidic pH, salt content, the presence of preservatives, emulsion characteristics, and nutrient deprivation. L. monocytogenes did not grow in six of the test products, but its population increased between 42 and 63 days in a butter-margarine blend stored at 10°C and between 3 and 7 days when the blend was stored at 21°C. On the basis of the experimental parameters examined in this study, traditional margarine and spreads not containing butter are not “potentially hazardous foods” in that they do not support the growth of Salmonella, E. coli O157:H7, or L. monocytogenes.

scholarly journals Environmental inactivation and irrigation-mediated regrowth of Escherichia coli O157:H7 on romaine lettuce when inoculated in a fecal slurry matrix

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6591 ◽  
Author(s):  
Jennifer A. Chase ◽  
Melissa L. Partyka ◽  
Ronald F. Bond ◽  
Edward R. Atwill
Keyword(s):  
Escherichia Coli ◽  
Field Trials ◽  
Inactivation Rate ◽  
Bacterial Inactivation ◽  
Romaine Lettuce ◽  
E Coli ◽  
Log Reduction ◽  
Salinas Valley ◽  
Kinetics Of ◽  
Insight Into

Field trials were conducted in July–August and October 2012 to quantify the inactivation rate of Escherichia coli O157:H7 when mixed with fecal slurry and applied to romaine lettuce leaves. Lettuce was grown under commercial conditions in Salinas Valley, California. One-half milliliter of rabbit, chicken, or pig fecal slurry, containing an average of 4.05 × 107 CFU E. coli O157:H7 (C0), was inoculated onto the upper (adaxial) surface of a lower leaf on 288 heads of lettuce per trial immediately following a 2.5 h irrigation event. To estimate the bacterial inactivation rate as a function of time, fecal matrix, irrigation and seasonal climate effects, sets of lettuce heads (n = 28) were sampled each day over 10 days and the concentration of E. coli O157:H7 (Ct) determined. E. coli O157:H7 was detected on 100% of heads during the 10-day duration, with concentrations ranging from ≤340 MPN/head (∼5-log reduction) to >3.45 × 1012 MPN/head (∼5-log growth). Relative to C0, on day 10 (Ct = 12) we observed an overall 2.6-log and 3.2-log mean reduction of E. coli O157:H7 in July and October, respectively. However, we observed relative maximum concentrations due to bacterial growth on day 6 (maximum Ct = 8) apparently stimulated by foliar irrigation on day 5. From this maximum there was a mean 5.3-log and 5.1-log reduction by day 10 (Ct = 12) for the July and October trials, respectively. This study provides insight into the inactivation and growth kinetics of E. coli O157:H7 on romaine lettuce leaves under natural field conditions. This study provides evidence that harvesting within 24 h post irrigation has the potential to increase the concentration of E. coli O157:H7 contamination, if present on heads of romaine lettuce; foliar irrigation can temporarily stimulate substantial regrowth of E. coli O157:H7.

scholarly journals Disinfection of Escherichia coli and Pseudomonas aeruginosa by copper in water

2016 ◽  
Vol 14 (3) ◽  
pp. 424-432 ◽  
Author(s):  
Andrew M. Armstrong ◽  
Mark D. Sobsey ◽  
Lisa M. Casanova
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Enteric Bacteria ◽  
Inactivation Kinetics ◽  
Log10 Reduction ◽  
E Coli ◽  
Piped Water ◽  
Ionic Copper ◽  
Household Water ◽  
Kinetics Of

When households lack access to continuous piped water, water storage in the home creates opportunities for contamination. Storage in copper vessels has been shown to reduce microbes, but inactivation kinetics of enteric bacteria in water by copper alone needs to be understood. This work characterized inactivation kinetics of Escherichia coli and Pseudomonas aeruginosa by dissolved ionic copper in water. Reductions of E. coli and P. aeruginosa increase with increasing dose. At 0.3 mg/L, there was a 2.5 log10 reduction of E. coli within 6 hours. At 1 and 3 mg/L, the detection limit was reached between 3 and 6 hours; maximum reduction measured was 8.5 log10. For P. aeruginosa, at 6 hours there was 1 log10 reduction at 0.3 mg/L, 3.0 log10 at 1 mg/L, and 3.6 log10 at 3 mg/L. There was no significant decline in copper concentration. Copper inactivates bacteria under controlled conditions at doses between 0.3 and 1 mg/L. E. coli was inactivated more rapidly than P. aeruginosa. Copper at 1 mg/L can achieve 99.9% inactivation of P. aeruginosa and 99.9999997% inactivation of E. coli over 6 hours, making it a candidate treatment for stored household water.

Inactivation kinetics of indicator microorganisms during urea treatment for sanitizing finished compost from composting toilet

2016 ◽  
Vol 6 (2) ◽  
pp. 269-275 ◽  
Author(s):  
Seyram K. Sossou ◽  
Mariam Sou/Dakoure ◽  
Yacouba Konate ◽  
Amadou H. Maiga ◽  
Naoyuki Funamizu
Keyword(s):  
Treatment Time ◽  
Urea Concentration ◽  
Inactivation Rate ◽  
Inactivation Kinetics ◽  
Kinetics Parameters ◽  
Urea Treatment ◽  
Indicator Microorganisms ◽  
E Coli ◽  
Kinetics Of ◽  
Linear Reduction

This study aimed at estimating the sanitizing effectiveness of urea treatment by studying the inactivation kinetics of selected indicator microorganisms. Finished composts from a composting toilet were inoculated with indicator microorganisms and subjected to different urea concentrations (0.5–2% w/w) and temperatures (22, 32 and 42°C). The inactivation kinetics parameters were determined in relation to pH, ammonia content and temperature during treatment time. The results show that urea addition to compost enhanced inactivation of microorganisms. The decline in number of E. coli and Enterococus followed a linear reduction, while that of Ascaris lumbricoides eggs followed a linear reduction plus shoulder. The inactivation rate constants of all microorganisms tested were positively correlated to the increase of NH3(aq) concentration and temperature. The relationship between the inactivation rate of microorganisms, ammonia through urea concentration and temperature were established. Therefore, the best decimal decay of E. coli, Enterococus and A. lumbricoides eggs occurred with 2% w/w urea concentration at 42°C within 0.9, 1.1 and 1.4 days, respectively. E. coli was the most sensitive microorganism to urea treatment, while Enterococcus and A. lumbricoides eggs showed resistance, especially at lower temperatures. Urea treatment has proved to be an efficient option for safe reuse of compost from composting toilets.

scholarly journals Reclaiming the Efficacy of β-Lactam–β-Lactamase Inhibitor Combinations: Avibactam Restores the Susceptibility of CMY-2-Producing Escherichia coli to Ceftazidime

2014 ◽  
Vol 58 (8) ◽  
pp. 4290-4297 ◽  
Author(s):  
Krisztina M. Papp-Wallace ◽  
Marisa L. Winkler ◽  
Julian A. Gatta ◽  
Magdalena A. Taracila ◽  
Sujatha Chilakala ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Rate Constant ◽  
Clinical Isolates ◽  
Inactivation Kinetics ◽  
Content Type ◽  
E Coli ◽  
Cephalosporin Resistance ◽  
Molecular Modeling Studies ◽  
Kinetics Of ◽  
Lactamase Inhibitor

ABSTRACTCMY-2 is a plasmid-encoded Ambler class C cephalosporinase that is widely disseminated inEnterobacteriaceaeand is responsible for expanded-spectrum cephalosporin resistance. As a result of resistance to both ceftazidime and β-lactamase inhibitors in strains carryingblaCMY, novel β-lactam–β-lactamase inhibitor combinations are sought to combat this significant threat to β-lactam therapy. Avibactam is a bridged diazabicyclo [3.2.1]octanone non-β-lactam β-lactamase inhibitor in clinical development that reversibly inactivates serine β-lactamases. To define the spectrum of activity of ceftazidime-avibactam, we tested the susceptibilities ofEscherichia coliclinical isolates that carryblaCMY-2orblaCMY-69and investigated the inactivation kinetics of CMY-2. Our analysis showed that CMY-2-containing clinical isolates ofE. coliwere highly susceptible to ceftazidime-avibactam (MIC90, ≤0.5 mg/liter); in comparison, ceftazidime had a MIC90of >128 mg/liter. More importantly, avibactam was an extremely potent inhibitor of CMY-2 β-lactamase, as demonstrated by a second-order onset of acylation rate constant (k2/K) of (4.9 ± 0.5) × 104M−1s−1and the off-rate constant (koff) of (3.7 ± 0.4) ×10−4s−1. Analysis of the reaction of avibactam with CMY-2 using mass spectrometry to capture reaction intermediates revealed that the CMY-2–avibactam acyl-enzyme complex was stable for as long as 24 h. Molecular modeling studies raise the hypothesis that a series of successive hydrogen-bonding interactions occur as avibactam proceeds through the reaction coordinate with CMY-2 (e.g., T316, G317, S318, T319, S343, N346, and R349). Our findings support the microbiological and biochemical efficacy of ceftazidime-avibactam againstE. colicontaining plasmid-borne CMY-2 and CMY-69.

scholarly journals Inactivation of Escherichia coli O157:H7 in Simulated Human Gastric Fluid

2005 ◽  
Vol 71 (1) ◽  
pp. 320-325 ◽  
Author(s):  
Mark L. Tamplin
Keyword(s):  
Escherichia Coli ◽  
Shigella Flexneri ◽  
Survival Rates ◽  
Gastric Fluid ◽  
Inactivation Rate ◽  
Host Susceptibility ◽  
E Coli ◽  
Average Survival ◽  
The Matrix ◽  
Kinetics Of

ABSTRACT Human disease caused by Escherichia coli O157:H7 is a function of the number of cells that are present at potential sites of infection and host susceptibility. Such infectious doses are a result, in part, of the quantity of cells that are ingested and that survive human host defenses, such as the low-pH environment of the stomach. To more fully understand the kinetics of E. coli O157:H7 survival in gastric fluid, individual E. coli O157:H7 strains were suspended in various media (i.e., saline, cooked ground beef [CGB], and CGB containing a commercial antacid product [CGB+A]), mixed at various proportions with simulated human gastric fluid (SGF), and then incubated at 37�C for up to 4 h. The highest inactivation rate among nine E. coli O157:H7 strains was observed in saline. Specifically, the average survival rates in 100:1 and 10:1 proportions of SGF-saline were −1.344 � 0.564 and −0.997 � 0.388 log10 CFU/h, respectively. In contrast, the average inactivation rate for 10 E. coli O157:H7 strains suspended in 10:1 SGF-CGB was −0.081 � 0.068, a rate that was 12-fold lower than that observed for SGF-saline. In comparison, the average inactivation rate for Shigella flexneri strain 5348 in 100:1 and 10:1 SGF-saline was −8.784 and −17.310, respectively. These latter inactivation rates were 7- to 17-fold higher than those for E. coli O157:H7 strains in SGF-saline and were 4-fold higher than those for E. coli O157:H7 strains in SGF-CGB. The survival rate of E. coli O157:H7 strain GFP80EC increased as the dose of antacid increased from one-half to twice the prescribed dose. A similar trend was observed for the matrix pH over the range of pH 1.6 to 5.7, indicating that pH is a primary factor affecting E. coli O157:H7 survival in SGF-CGB+A. These results can be used in risk assessment to define dose-response relationships for E. coli O157:H7 and to evaluate potential surrogate organisms.

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