The Relationship Between Two Apparently Different Enterotoxins Produced By Enteropathogenic Strains Of Escherichia Coli Of Porcine Origin

Abstract Hydrogen peroxide (H2O2) is a debriding agent that damages the microbial structure and function by generating various reactive oxygen species (ROS). H2O2-produced hydroxyl radical (OH∙) also exert oxidative stress on microorganisms. The spread of antibiotic resistance in bacteria is a serious issue worldwide, and greater efforts are needed to identify and characterize novel antibacterial mechanisms to develop new treatment strategies. Therefore, this study aimed to clarify the relationship between H2O2 and Escherichia coli and to elucidate a novel antibacterial mechanism(s) of H2O2. Following H2O2 exposure, increased levels of 8-hydroxyldeoxyguanosine and malondialdehyde indicated that H2O2 accelerates oxidation of bacterial DNA and lipids in E. coli. As oxidative damage worsened, the SOS response was triggered. Cell division arrest and resulting filamentation were identified in cells, indicating that LexA was involved in DNA replication. It was also verified that RecA, a representative SOS gene, helps self-cleavage of LexA and acts as a bacterial caspase-like protein. Our findings also showed that dinF is essential to preserve E. coli from H2O2-induced ROS, and furthermore, demonstrated that H2O2-induced SOS response and SOS genes participate differently in guarding E. coli from oxidative stress. As an extreme SOS response is considered apoptosis-like death (ALD) in bacteria, additional experiments were performed to examine the characteristics of ALD. DNA fragmentation and membrane depolarization appeared in H2O2-treated cells, suggesting that H2O2 causes ALD in E. coli. In conclusion, our investigations revealed that ALD is a novel antibacterial mode of action(s) of H2O2 with important contributions from SOS genes.

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Survival of Escherichia coli on Lettuce under Field Conditions Encountered in the Northeastern United States

Journal of Food Protection ◽

10.4315/0362-028x.jfp-16-419 ◽

2017 ◽

Vol 80 (7) ◽

pp. 1214-1221 ◽

Cited By ~ 17

Author(s):

Daniel L. Weller ◽

Jasna Kovac ◽

Sherry Roof ◽

David J. Kent ◽

Jeffrey I. Tokman ◽

...

Keyword(s):

Escherichia Coli ◽

Microbial Contamination ◽

Field Conditions ◽

Risk Assessments ◽

Most Probable Number ◽

Northeastern United States ◽

Probable Number ◽

E Coli ◽

The Relationship ◽

Sample Time

ABSTRACT Although wildlife intrusion and untreated manure have been associated with microbial contamination of produce, relatively few studies have examined the survival of Escherichia coli on produce under field conditions following contamination (e.g., via splash from wildlife feces). This experimental study was performed to estimate the die-off rate of E. coli on preharvest lettuce following contamination with a fecal slurry. During August 2015, field-grown lettuce was inoculated via pipette with a fecal slurry that was spiked with a three-strain cocktail of rifampin-resistant nonpathogenic E. coli. Ten lettuce heads were harvested at each of 13 time points following inoculation (0, 2.5, 5, and 24 h after inoculation and every 24 h thereafter until day 10). The most probable number (MPN) of E. coli on each lettuce head was determined, and die-off rates were estimated. The relationship between sample time and the log MPN of E. coli per head was modeled using a segmented linear model. This model had a breakpoint at 106 h (95% confidence interval = 69, 142 h) after inoculation, with a daily decrease of 0.70 and 0.19 log MPN for 0 to 106 h and 106 to 240 h following inoculation, respectively. These findings are consistent with die-off rates obtained in similar studies that assessed E. coli survival on produce following irrigation. Overall, these findings provide die-off rates for E. coli on lettuce that can be used in future quantitative risk assessments.

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Distribution of Coliphages in Various Foods

Journal of Food Protection ◽

10.4315/0362-028x-49.12.944 ◽

1986 ◽

Vol 49 (12) ◽

pp. 944-951 ◽

Cited By ~ 30

Author(s):

J. E. KENNEDY ◽

C. I. WEI ◽

J. L. OBLINGER

Keyword(s):

Escherichia Coli ◽

Food Samples ◽

Fecal Coliforms ◽

Bacterial Indicators ◽

Processed Meats ◽

E Coli ◽

Plate Counts ◽

The Relationship

The distribution of coliphages in various foods and the relationship between the incidences of coliphages and bacterial indicators were investigated. A total of 120 food samples comprising twelve products and including fresh meats, shellfish, vegetables and processed meats, were analyzed for indigenous coliphages using Escherichia coli hosts C, C-3000 and B. Bacterial analyses included enumeration of E. coli, fecal coliforms and coliforms, as well as aerobic plate counts and Salmonella analyses. Coliphages were detected (≥10 PFU/100 g) in 56% of samples and eleven of twelve products. Coliphages, E. coli, fecal coliforms and coliforms were recovered at a level of at least 30 organisms per 100 g in 43, 43, 68 and 81% of samples, with overall mean recoveries of 13, 19, 93 and 4300 organisms/100 g, respectively. Highest and lowest recoveries of coliphages and E. coli were from fresh meats and vacuum-packaged processed meats, respectively. Significant nonparametric correlations between coliphages, E. coli, fecal coliforms and coliforms were found among all food samples.

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Molecular analysis of Escherichia coli O157 strains isolated from cattle and pigs by the use of PCR and pulsed-field gel electrophoresis methods

Veterinární Medicína ◽

10.17221/5819-vetmed ◽

2012 ◽

Vol 47 (No. 6) ◽

pp. 149-158 ◽

Cited By ~ 15

Author(s):

J. Osek ◽

P. Gallien

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Genetic Relatedness ◽

Rflp Analysis ◽

Toxin Gene ◽

Escherichia Coli O157 ◽

Chromosomal Dna ◽

E Coli ◽

Shiga Toxin Genes ◽

Porcine Origin

Fourteen Escherichia coli O157 strains isolated from cattle and pigs in Poland and in Germany were investigated, using PCR, for the genetic markers associated with Shiga toxin-producing E. coli (STEC). Only two strains, both of cattle origin, were positive for the fliC (H7) gene and could be classified as O157 : H7. Nine isolates had stx shiga toxin genes, either stx1 (1 strain), stx2 (4 isolates) or both (4 strains). The stx2-carrying samples were further subtyped by PCR for the stx2c, stx2d, and stx2e toxin variants. It was shown that all but one stx2-positive bacteria possessed the stx2c Shiga toxin gene type and one stx2 STEC isolate had the stx2d virulence factor sub-type. The eaeA (intimin) gene was found in 9 strains (8 isolates from cattle and one strain from pigs); all of them harboured the genetic marker characteristic of the gamma intimin variant. The translocated intimin receptor (tir) gene was detected in 7 isolates tested and among them only one tir-positive strain was recovered from pigs. The ehly E. coli enterohemolysin gene was amplified in all but one strains obtained from cattle and only in one isolate of porcine origin. The genetic relatedness of the analysed E. coli O157 strains was examined by restriction fragment length polymorphism (RFLP) of chromosomal DNA digested with XbaI. Two distinct but related RFLP pattern clusters were observed: one with 9 strains (8 isolates of bovine origin and one strain obtained from pigs) and the other one comprises the remaining 5 E. coli isolates (4 of porcine origin and one strain recovered from cattle). The results suggest that pigs, besides cattle, may be a reservoir of E. coli O157 strains potentially pathogenic to humans. Moreover, epidemiologically unrelated isolates of the O157 serogroup, recovered from different animal species, showed a clonal relationship as demonstrated by the RFLP analysis.

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The Feedback Response of Escherichia coli rRNA Synthesis Is Not Identical to the Mechanism of Growth Rate-Dependent Control

Journal of Bacteriology ◽

10.1128/jb.182.2.536-539.2000 ◽

2000 ◽

Vol 182 (2) ◽

pp. 536-539 ◽

Cited By ~ 8

Author(s):

Justina Voulgaris ◽

Dmitry Pokholok ◽

W. Mike Holmes ◽

Craig Squires ◽

Catherine L. Squires

Keyword(s):

Escherichia Coli ◽

Growth Rate ◽

Gene Dosage ◽

Rrna Synthesis ◽

Rate Dependent ◽

Nucleoside Triphosphates ◽

The Relationship ◽

Mechanism Of Growth

ABSTRACT Growth rate-independent rrn P1 promoter mutants were tested for their ability to respond to changes in rrn gene dosage. Most were found to be normal for the feedback response. In addition, cellular levels of the initiating nucleoside triphosphates remained unchanged when the rrn gene dosage was altered. These results suggest that the feedback response cannot be the mechanism for growth rate-dependent control of rRNA synthesis and that the relationship between these two processes may be more complicated than is currently understood.

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