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"O157"
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Essential Oils and Eugenols Inhibit Biofilm Formation and the Virulence of Escherichia coli O157:H7
Enterohemorrhagic
Escherichia coli
O157:H7 (EHEC) has caused foodborne outbreaks worldwide and the bacterium forms antimicrobial-tolerant biofilms. We investigated the abilities of various plant essential oils and their components to inhibit biofilm formation by EHEC. Bay, clove, pimento berry oils and their major common constituent eugenol at 0.005% (v/v) were found to markedly inhibit EHEC biofilm formation without affecting planktonic cell growth. In addition, three other eugenol derivatives isoeugenol, 2-methoxy-4-propylphenol, and 4-ethylguaiacol had antibiofilm activity, indicating that the C-1 hydroxyl unit, the C-2 methoxy unit, and C-4 alkyl or alkane chain on the benzene ring of eugenol play important roles in antibiofilm activity. Interestingly, these essential oils and eugenol did not inhibit biofilm formation by three laboratory
E. coli
K-12 strains that reduced curli fimbriae production. Transcriptional analysis showed that eugenol down-regulated 17 of 28 genes analysed, including curli genes (
csgABDFG
), type I fimbriae genes (
fimCDH
) and
ler
-controlled toxin genes (
espD
,
escJ
,
escR
, and
tir
), which are required for biofilm formation and the attachment and effacement phenotype. In addition, biocompatible poly(lactic-co-glycolic acid) coatings containing clove oil or eugenol exhibited efficient biofilm inhibition on solid surfaces. In a
Caenorhabditis elegans
nematode model, clove oil and eugenol attenuated the virulence of EHEC.
Journal Article
Variation in virulence among clades of Escherichia coli O157:H7 associated with disease outbreaks
Escherichia coli O157:H7, a toxin-producing food and waterborne bacterial pathogen, has been linked to large outbreaks of gastrointestinal illness for more than two decades. E. coli O157 causes a wide range of clinical illness that varies by outbreak, although factors that contribute to variation in disease severity are poorly understood. Several recent outbreaks involving O157 contamination of fresh produce (e.g., spinach) were associated with more severe disease, as defined by higher hemolytic uremic syndrome and hospitalization frequencies, suggesting that increased virulence has evolved. To test this hypothesis, we developed a system that detects SNPs in 96 loci and applied it to >500 E. coli O157 clinical strains. Phylogenetic analyses identified 39 SNP genotypes that differ at 20% of SNP loci and are separated into nine distinct clades. Differences were observed between clades in the frequency and distribution of Shiga toxin genes and in the type of clinical disease reported. Patients with hemolytic uremic syndrome were significantly more likely to be infected with clade 8 strains, which have increased in frequency over the past 5 years. Genome sequencing of a spinach outbreak strain, a member of clade 8, also revealed substantial genomic differences. These findings suggest that an emergent subpopulation of the clade 8 lineage has acquired critical factors that contribute to more severe disease. The ability to detect and rapidly genotype O157 strains belonging to such lineages is important and will have a significant impact on both disease diagnosis and treatment guidelines.
Journal Article
Characterization and Food Application of the Novel Lytic Phage BECP10: Specifically Recognizes the O-polysaccharide of Escherichia coli O157:H7
Escherichia coli O157:H7 is a global concern that causes serious diseases, such as hemolytic uremic syndrome and bloody diarrhea. To control E. coli O157:H7 in food, a novel siphophage, BECP10, that targets the O157 serotype was isolated and characterized. Unlike other E. coli phages, BECP10 can only infect E. coli O157 strains, and thus, did not infect other strains. The 48 kbp genome of BECP10 contained 76 open reading frames (ORFs), including 33 putative functional ORFs. The phage did not contain lysogeny-related modules or toxin-associated genes, suggesting that the phage might be strictly lytic. The tail spike protein (TSP) sequence had very low homology with the reported T1-like phages, indicating that TSP might be related to this unique host spectrum. The specific O-antigen residue of E. coli O157:H7 may be a key factor for phage infection by adsorption and receptor identification. The phage exhibited strong antibacterial activity against E. coli O157:H7 over a broad pH range and showed little development of phage-insensitive mutants. The phage sustained viability on the burger patties and reduced E. coli O157:H7 to a non-detectable level without the emergence of resistant cells at low temperatures for five days. Therefore, phage BECP10 might be a good biocontrol agent for E. coli O157:H7-contaminated food matrices.
Journal Article
Nanoplastics-mediated physiologic and genomic responses in pathogenic Escherichia coli O157:H7
The widespread occurrence of microplastics (MP) and nanoplastics (NP) in the environment is commonly thought to negatively impact living organisms; however, there remains a considerable lack of understanding regarding the actual risks associated with exposure. Microorganisms, including pathogenic bacteria, frequently interact with MPs/NPs in various ecosystems, triggering physiological responses that warrant a deeper understanding. The present study experimentally demonstrated the impact of surface-functionalized differentially charged polystyrene (PS) NPs on the physiology of human pathogenic
Escherichia coli
O157:H7 and their influence on biofilm formation. Our results suggest that charged NPs can influence the growth, viability, virulence, physiological stress response, and biofilm lifestyle of the pathogen. Positively-charged NPs were found to have a bacteriostatic effect on planktonic cell growth and affect cellular viability and biofilm initiation compared to negatively charged and uncharged NPs. The transcriptomic and gene expression data indicated significant changes in the global gene expression profile of cells exposed to NPs, including the differential expression of genes encoding several metabolic pathways associated with stress response and virulence. Significant upregulation of Shiga-like toxin (
stx
1a
), quorum sensing, and biofilm initiation genes was observed in NP-exposed biofilm samples. Overall, exposure to NPs did not significantly affect the survival of pathogens but affected their growth and biofilm development pattern, and most importantly, their virulence traits.
Graphical abstract
Journal Article
A Dual-mode platform for the rapid detection of Escherichia coli O157:H7 based on CRISPR/Cas12a and RPA
Escherichia coli O157:H7 (E. coli O157:H7) is a foodborne pathogenic microorganism that is commonly found in the environment and poses a significant threat to human health, public safety, and economic stability worldwide. Thus, early detection is essential for E. coli O157:H7 control. In recent years, a series of E. coli O157:H7 detection methods have been developed, but the sensitivity and portability of the methods still need improvement. Therefore, in this study, a rapid and efficient testing platform based on the CRISPR/Cas12a cleavage reaction was constructed. Through the integration of recombinant polymerase amplification and lateral flow chromatography, we established a dual-interpretation-mode detection platform based on CRISPR/Cas12a-derived fluorescence and lateral flow chromatography for the detection of E. coli O157:H7. For the fluorescence detection method, the limits of detection (LODs) of genomic DNA and E. coli O157:H7 were 1.8 fg/µL and 2.4 CFU/mL, respectively, within 40 min. Conversely, for the lateral flow detection method, LODs of 1.8 fg/µL and 2.4 × 102 CFU/mL were achieved for genomic DNA and E. coli O157:H7, respectively, within 45 min. This detection strategy offered higher sensitivity and lower equipment requirements than industry standards. In conclusion, the established platform showed excellent specificity and strong universality. Modifying the target gene and its primers can broaden the platform’s applicability to detect various other foodborne pathogens.
Journal Article
Study on the mechanism of antibacterial action of magnesium oxide nanoparticles against foodborne pathogens
Background
Magnesium oxide nanoparticles (MgO nanoparticles, with average size of 20 nm) have considerable potential as antimicrobial agents in food safety applications due to their structure, surface properties, and stability. The aim of this work was to investigate the antibacterial effects and mechanism of action of MgO nanoparticles against several important foodborne pathogens.
Results
Resazurin (a redox sensitive dye) microplate assay was used for measuring growth inhibition of bacteria treated with MgO nanoparticles. The minimal inhibitory concentrations of MgO nanoparticles to 10
4
colony-forming unit/ml (CFU/ml) of
Campylobacter jejuni
,
Escherichia coli
O157:H7, and
Salmonella
Enteritidis were determined to be 0.5, 1 and 1 mg/ml, respectively. To completely inactivate 10
8−9
CFU/ml bacterial cells in 4 h, a minimal concentration of 2 mg/ml MgO nanoparticles was required for
C. jejuni
whereas
E. coli
O157:H7 and
Salmonella
Enteritidis required at least 8 mg/ml nanoparticles. Scanning electron microscopy examination revealed clear morphological changes and membrane structural damage in the cells treated with MgO nanoparticles. A quantitative real-time PCR combined with ethidium monoazide pretreatment confirmed cell membrane permeability was increased after exposure to the nanoparticles. In a cell free assay, a low level (1.1 μM) of H
2
O
2
was detected in the nanoparticle suspensions. Consistently, MgO nanoparticles greatly induced the gene expression of KatA, a sole catalase in
C. jejuni
for breaking down H
2
O
2
to H
2
O and O
2
.
Conclusions
MgO nanoparticles have strong antibacterial activity against three important foodborne pathogens. The interaction of nanoparticles with bacterial cells causes cell membrane leakage, induces oxidative stress, and ultimately leads to cell death.
Journal Article
Genomic Characterization of Escherichia coli O157:H7 Associated with Multiple Sources, United States
In the United States, Shiga toxin-producing Escherichia coli (STEC) outbreaks cause >265,000 infections and cost $280 million annually. We investigated REPEXH01, a persistent strain of STEC O157:H7 associated with multiple sources, including romaine lettuce and recreational water, that has caused multiple outbreaks since emerging in late 2015. By comparing the genomes of 729 REPEXH01 isolates with those of 2,027 other STEC O157:H7 isolates, we identified a highly conserved, single base pair deletion in espW that was strongly linked to REPEXH01 membership. The biological consequence of that deletion remains unclear; further studies are needed to elucidate its role in REPEXH01. Additional analyses revealed that REPEXH01 isolates belonged to Manning clade 8; possessed the toxins stx2a, stx2c, or both; were predicted to be resistant to several antimicrobial compounds; and possessed a diverse set of plasmids. Those factors underscore the need to continue monitoring REPEXH01 and clarify aspects contributing to its emergence and persistence.
Journal Article
Genetic profiling of extended-spectrum β-Lactamase and carbapenemase-producing Escherichia coli O157:H7 from clinical samples among diarrheal patients in Shashemene, Ethiopia
Background
Escherichia coli (E. coli)
O157:H7, associated with diarrhea, poses a global health risk. In Ethiopia, where diarrhea is common, there is limited knowledge about these resistant strains and a lack of data on Extended-Spectrum β-Lactamase (ESBL) and carbapenemase production. Understanding the prevalence of antimicrobial resistance genes associated with ESBL and carbapenems is crucial for addressing diarrheal disease. This study aimed to investigate the genetic profile of ESBL and carbapenemase coding gene carriage in
E. coli
O157:H7 from clinical stool samples and evaluate antimicrobial susceptibility patterns.
Methods
A total of twenty-nine bacterial isolates obtained from diarrheal patients were subjected to conventional culture and phenotypic (Kirby Bauer disc diffusion method) testing for antimicrobial resistance. Additionally, screening for the production of ESBL (combined disk method) and carbapenemase (modified carbapenem inactivation method) was conducted. Isolates that tested positive for ESBL and carbapenemase production were further analyzed, targeting five genes (
bla
NDM
,
bla
KPC
,
bla
CTX−M
,
bla
TEM
, and
bla
SHV
) associated with ESBL and carbapenemase production. Data analysis was performed using SPSS version 27.0, employing logistic regression and descriptive statistics.
Results
We analyzed a total of 27 isolates that were ESBL-positive and 12 isolates that were found to produce carbapenemase phenotypically. These isolates were obtained from clinical stool samples and (9/27) 33.3% of the isolates were from under five years children, predominantly from urban areas, and those that have contact with domestic animals. Genes coding ESBL were found in (19/27) 70.4% of the isolates, the most predominant being
bla
CTX−M
and
bla
TEM
. Eight isolates carried
bla
KPC
, but none had
bla
NDM
, while five isolates carried both
bla
CTX−M
and
bla
TEM
genes.
bla
SHV
-carrying isolates showed phenotypic resistance to ampicillin and cephalosporins, while
bla
KPC
-carrying isolates exhibited resistance to ampicillin, carbapenems, and tetracycline.
Conclusion
This study identifies a significant prevalence of multidrug resistance in
E. coli
O157:H7, which can be attributed to the presence of resistance genes coding for ESBL and carbapenem production. Key factors contributing to this resistance, such as urban environments, children under the age of five, and domestic animal ownership, have been emphasized. Additionally, this research underscores the urgent need for enhanced surveillance and targeted interventions to address this pressing public health concern.
Journal Article
The Protective Effects of 2’-Fucosyllactose Against E. Coli O157 Infection Are Mediated by the Regulation of Gut Microbiota and the Inhibition of Pathogen Adhesion
As the richest component in human milk oligosaccharides (HMOs), 2’-fucosyllactose (2’-FL) can reduce the colonization of harmful microbiota in vivo, thus lowering the risk of infection; however, the mechanism for this is still unclear. In this study, a model of Escherichia coli O157 infection in healthy adult mice was established to explore the effect of 2’-FL intervention on E. coli O157 colonization and its protective effects on mice. The results showed that 2’-FL intake reduced E. coli O157 colonization in mice intestine by more than 90% (p < 0.001), and it also reduced intestinal inflammation, increased the content of fecal short-chain fatty acids, and enhanced intestinal barrier function. These beneficial effects were attributed to the increased expression of mucins such as MUC2 (increased by more than 20%, p < 0.001), and inhibition of E. coli O157 cell adhesion (about 30% reduction, p < 0.001), and were associated with the modulation of gut microbiota composition. 2’-FL significantly increased the abundance of Akkermansia, a potential probiotic, which may represent the fundamental means by which 2’-FL enhances the expression of mucin and reduces the colonization of harmful bacteria. The current study may support the use of 2’-FL in the prevention of foodborne pathogen infections in human.
Journal Article