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.

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 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.

scholarly journals Reclassification of Shigella species as later heterotypic synonyms of Escherichia coli in the Genome Taxonomy Database

2021 ◽  
Author(s):  
Donovan H Parks ◽  
Maria Chuvochina ◽  
Peter R Reeves ◽  
Scott A Beatson ◽  
Philip Hugenholtz
Keyword(s):  
Escherichia Coli ◽  
Type Strain ◽  
Shigella Flexneri ◽  
Laboratory Strain ◽  
Single Species ◽  
Species Definition ◽  
E Coli ◽  
Shigella Species ◽  
K 12 ◽  
Common Laboratory

Members of the genus Shigella have high genomic similarity to Escherichia coli and are often considered to be atypical members of this species. In an attempt to retain Shigella species as recognizable entities, they were reclassified as Escherichia species in the Genome Taxonomy Database (GTDB) using an operational average nucleotide identity (ANI)-based approach nucleated around type strains. This resulted in nearly 80% of E. coli genomes being reclassified to new species including the common laboratory strain E. coli K-12 (to 'E. flexneri') because it is more closely related to the type strain of Shigella flexneri than it is to the type strain of E. coli. Here we resolve this conundrum by treating Shigella species as later heterotypic synonyms of E. coli, present evidence supporting this reclassification, and show that assigning E. coli/Shigella strains to a single species is congruent with the GTDB-adopted genomic species definition.

Escherichia coli O157 Diversity with Respect to Survival during Drying on Concrete

2003 ◽  
Vol 66 (5) ◽  
pp. 780-786 ◽  
Author(s):  
S. M. AVERY ◽  
S. BUNCIC
Keyword(s):  
Escherichia Coli ◽  
Survival Rate ◽  
Phage Type ◽  
Survival Rates ◽  
Pfge Type ◽  
Meat Production ◽  
Escherichia Coli O157 ◽  
Production Chain ◽  
E Coli ◽  
Wide Range

Shiga toxin (Stx)–producing Escherichia coli O157 isolates (n = 123) were divided into groups according to origin, genotype (pulsed-field gel electrophoresis [PFGE] type, or ribotype), type of Stx produced, or phage type (PT). The survival rate ([number of CFU after 24 h of drying/number of CFU before drying] × 100) for each isolate was determined in triplicate after drying on concrete for 24.0 h. The overall mean survival rate among the 123 E. coli O157 isolates studied was 22.9%, but there was a wide range of responses to drying on concrete, with a minimum of 1.2% and a maximum of 61.9% of the initial inocula being recovered after drying. Among the groups, those isolates that originated from cases of human disease were, on average, significantly more sensitive (P < 0.001) to drying (with a mean survival rate of 15.3%) than isolates from the other three sources (with mean survival rates of 27.7, 26.0, and 22.9% for meats, bovine or ovine feces, and bovine hides, respectively). When the isolates were grouped by genotype, three of the PFGE types were, on average, significantly more resistant to drying than two other PFGE types were, and similarly, significant differences in average resistance to drying between groups of E. coli O157 with different ribotypes were seen. There were no differences between the abilities of isolates producing different Stxs (Stx 1 or Stx 1 and Stx 2) to survive drying. E. coli O157 isolates of PT4, PT21/28, and PT32 survived drying on concrete better than groups of other PTs did. Since the E. coli O157 isolates had various abilities to survive drying on concrete, drying could contribute to a kind of E. coli O157 natural selection along the meat chain. This possibility may have significant meat safety implications if a range of E. coli O157 isolates are simultaneously exposed to drying at any point along the meat production chain. Those E. coli O157 isolates that are more able to survive drying could be more likely to pass farther along the meat chain and ultimately reach consumers.

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.

scholarly journals Inactivation of Escherichia coli and Staphyloccocus aureus in Litchi Juice by Dimethyl Dicarbonate (DMDC) Combined With Nisin

2014 ◽  
Vol 3 (3) ◽  
pp. 1 ◽  
Author(s):  
Yuanshan Yu ◽  
Yujuan Xu ◽  
Jijun Wu ◽  
Gengsheng Xiao ◽  
Jing Wen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Synergistic Effect ◽  
Ph Value ◽  
Inactivation Rate ◽  
Gram Positive ◽  
Gram Negative ◽  
E Coli ◽  
Complete Inactivation ◽  
Staphyloccocus Aureus ◽  
Addition Level

<p>Inactivation of Gram-negative <em>Escherichia coli</em> and Gram-positive <em>Staphyloccocus aureus</em> in litchi juice by DMDC combined with nisin was individually investigated. A 1.66 log cycles reduction of<em> E. coli </em>and 2.03 log cycles reduction of <em>S. aureus </em>in litchi juice (pH 4.5) added without nisin was achieved as exposed to 150 mg/l DMDC at 30 °C for 1 h, and the inactivation rate of <em>E. coli </em>and <em>S. aureus</em> during initial 1 h was far greater than during the remaining 5 h. As exposed to 150 mg/l DMDC at 30 °C for 1 h, the inactivation of <em>E. coli</em> and <em>S. aureus</em> in the litchi juice showed a trend toward increase with increasing of nisin addition level in the range from 0 to 200 IU/ml. Moreover, DMDC and nisin exhibited a synergistic effect on the inactivation of <em>E. coli</em> and <em>S. aureus</em> in litchi juice, and the inactivation of<em> E. coli</em> and <em>S. aureus</em> in the litchi juice also depends on the temperature of litchi juice, pH value of litchi juice and DMDC concentration when treated with DMDC and nisin. In addition, <em>E. coli</em> showed higher resistance to nisin as comparing with <em>S. aureus</em>. After <em>E. coli</em> and <em>S. aureus</em> in the litchi juice of pH 4.0 were individually treated with 150 mg/l DMDC combined with 200 IU/ml nisin at 30 °C for 1 h, a complete inactivation of <em>S. aureus</em> (6.59 log cycles) was achieved, but only 3.52 log cycles reduction of <em>E. coli</em> was observed.</p>

scholarly journals Genomic Subtraction To Identify and Characterize Sequences of Shiga Toxin-Producing Escherichia coli O91:H21

2002 ◽  
Vol 68 (5) ◽  
pp. 2316-2325 ◽  
Author(s):  
Nathalie Pradel ◽  
Sabine Leroy-Setrin ◽  
Bernard Joly ◽  
Valérie Livrelli
Keyword(s):  
Escherichia Coli ◽  
Dna Sequences ◽  
Shiga Toxin ◽  
Shigella Flexneri ◽  
Virulence Determinants ◽  
E Coli ◽  
Virulence Plasmids ◽  
Subtraction Procedure ◽  
Uremic Syndrome ◽  
Genomic Subtraction

ABSTRACT To identify Shiga toxin-producing Escherichia coli genes associated with severe human disease, a genomic subtraction technique was used with hemolytic-uremic syndrome-associated O91:H21 strain CH014 and O6:H10 bovine strains. The method was adapted to the Shiga toxin-producing E. coli genome: three rounds of subtraction were used to isolate DNA fragments specific to strain CH014. The fragments were characterized by genetic support analysis, sequencing, and hybridization to the genome of a collection of Shiga toxin-producing E. coli strains. A total of 42 fragments were found, 19 of which correspond to previously identified unique DNA sequences in the enterohemorrhagic E. coli EDL933 reference strain, including 7 fragments corresponding to prophage sequences and others encoding candidate virulence factors, such a SepA homolog protein and a fimbrial usher protein. In addition, the subtraction procedure yielded plasmid-related sequences from Shigella flexneri and enteropathogenic and Shiga toxin-producing E. coli virulence plasmids. We found that lateral gene transfer is extensive in strain CH014, and we discuss the role of genomic mobile elements, especially bacteriophages, in the evolution and possible transfer of virulence determinants.

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 &gt;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 &gt;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 Identification of Escherichia coli and Shigella Species from Whole-Genome Sequences

2016 ◽  
Vol 55 (2) ◽  
pp. 616-623 ◽  
Author(s):  
Marie A. Chattaway ◽  
Ulf Schaefer ◽  
Rediat Tewolde ◽  
Timothy J. Dallman ◽  
Claire Jenkins
Keyword(s):  
Escherichia Coli ◽  
Clonal Complex ◽  
Shigella Flexneri ◽  
Bacterial Species ◽  
Whole Genome ◽  
Content Type ◽  
E Coli ◽  
Shigella Species ◽  
Close Phylogenetic Relationship ◽  
Initial Identification

ABSTRACTEscherichia coliandShigellaspecies are closely related and genetically constitute the same species. Differentiating between these two pathogens and accurately identifying the four species ofShigellaare therefore challenging. The organism-specific bioinformatics whole-genome sequencing (WGS) typing pipelines at Public Health England are dependent on the initial identification of the bacterial species by use of a kmer-based approach. Of the 1,982Escherichia coliandShigellasp. isolates analyzed in this study, 1,957 (98.4%) had concordant results by both traditional biochemistry and serology (TB&S) and the kmer identification (ID) derived from the WGS data. Of the 25 mismatches identified, 10 were enteroinvasiveE. coliisolates that were misidentified asShigella flexneriorS. boydiiby the kmer ID, and 8 wereS. flexneriisolates misidentified by TB&S asS. boydiidue to nonfunctionalS. flexneriO antigen biosynthesis genes. Analysis of the population structure based on multilocus sequence typing (MLST) data derived from the WGS data showed that the remaining discrepant results belonged to clonal complex 288 (CC288), comprising bothS. boydiiandS. dysenteriaestrains. Mismatches between the TB&S and kmer ID results were explained by the close phylogenetic relationship between the two species and were resolved with reference to the MLST data.Shigellacan be differentiated fromE. coliand accurately identified to the species level by use of kmer comparisons and MLST. Analysis of the WGS data provided explanations for the discordant results between TB&S and WGS data, revealed the true phylogenetic relationships between different species ofShigella, and identified emerging pathoadapted lineages.

scholarly journals Isolation and characterization of a novel bacteriophage, Kapi1, capable of O-antigen modification in commensal Escherichia coli.

2021 ◽  
Author(s):  
Kat Pick ◽  
Tracy Lyn Raivio
Keyword(s):  
Escherichia Coli ◽  
Molecular Mechanisms ◽  
Shigella Flexneri ◽  
Model System ◽  
Temperate Phage ◽  
Phage Displays ◽  
E Coli ◽  
O Antigen ◽  
Isolation And Characterization

In this study, we describe the isolation and characterization of novel bacteriophage Kapi1 (vB_EcoP_Kapi1) isolated from a strain of commensal Escherichia coli inhabiting the gastrointestinal tract of healthy mice. We show that Kapi1 is a temperate phage integrated into tRNA argW of strain MP1 and describe its genome annotation and structure. Kapi1 shows limited homology to other characterized prophages but is most similar to the phages of Shigella flexneri, and clusters taxonomically with P22-like phages. Investigation of the lifestyle of Kapi1 shows that this phage displays unstable lysogeny and influences the growth of its host. The receptor for Kapi1 is the lipopolysaccharide O-antigen, and we further show that Kapi1 alters the structure of its hosts O-antigen in multiple ways. We hope to use MP1 and Kapi1 as a model system to explore molecular mechanisms of mammalian colonization by E. coli and ask what the role(s) of prophages in this context might be.

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