Escherichia Coli O157
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2022 ◽  
Vol 10 (1) ◽  
pp. 106
Rim Al Safadi ◽  
Michelle L. Korir ◽  
Shannon D. Manning

Escherichia coli O157:H7 pathogenesis is due to Shiga toxin (Stx) production, though variation in virulence has been observed. Clade 8 strains, for instance, were shown to overproduce Stx and were more common among hemolytic uremic syndrome cases. One candidate gene, norV, which encodes a nitric oxide (NO) reductase found in a clade 8 O157:H7 outbreak strain (TW14359), was thought to impact virulence. Hence, we screened for norV in 303 O157 isolates representing multiple clades, examined stx2 expression following NO exposure in TW14359 for comparison to an isogenic mutant (ΔnorV), and evaluated survival in THP-1 derived macrophages. norV was intact in strains representing clades 6–9, whereas a 204 bp deletion was found in clades 2 and 3. During anaerobic growth, NO induced stx2 expression in TW14359. A similar increase in stx2 expression was observed for the ΔnorV mutant in anaerobiosis, though it was not impaired in its ability to survive within macrophages relative to TW14359. Altogether, these data suggest that NO enhances virulence by inducing Stx2 production in TW14359, and that toxin production is inhibited by NorV encoded by a gene found in most clade 8 strains. The mechanism linked to these responses, however, remains unclear and likely varies across genotypes.

2022 ◽  
pp. 103978
Sander Witte ◽  
Linda Huijboom ◽  
Silvia Klamert ◽  
Leoni van de Straat ◽  
Steven Hagens ◽  

2021 ◽  
Vol 4 (2) ◽  
pp. 11-16
A.H. Jauro ◽  
I. Shu’aibu ◽  
G. Lawan ◽  
M.T. Adamu ◽  
M.Y. Iliyasu ◽  

The development of biofilms by the foodborne pathogens attached to surfaces in the food processing environments results in the deterioration of products, persistence of pathogenic bacteria and transmission of food-associated diseases. In addition, biofilms are more resistant to antimicrobials than their planktonic counterparts which make their elimination from food and the food processing facilities a great challenge. This study aim was to determine the inhibitory effect of food additives on biofilm forming Escherichia coli O157:H7. The isolate obtained was subjected to Gram’s staining and various biochemical identifications and later confirmed by latex agglutination test. Biofilm formation potential was done on Congo red media and the confirmed biofilm former was subjected to biofilm formation at 10℃ and 37℃ for 168hrs. Antimicrobial susceptibility testing, MIC, MBC, and antibiofilm effect was determined following CLSI 2017 guideline. The highest zone of growth inhibition of 31 mm was exhibited by cinnamaldehyde, sodium nitrite with 26 mm and sodium citrate with 13 mm. The MIC 2.5 mg/mL was recorded for sodium citrate, 0.25 mg/mL for sodium nitrite and 0.125 μl/mL for cinnamaldehyde. Strong biofilm was formed at 37 ℃ with 7.82 x 109 CFU/mL viable cells at 168hrs while 6.79 x 109 CFU/mL were obtained at 10 ℃. All the three additives showed antibiofilm effect (at 10℃ and 37℃), cinnamaldehyde exhibited 70%-90.1%, sodium nitrite; 70%-88.2% inhibition and sodium nitrite; 75%-88% inhibition respectively. This study showed that sodium citrate, sodium nitrite and cinnamaldehyde exerted strong antimicrobial and antibiofilm properties indicating their potential as good preservatives.

2021 ◽  
Michael Love ◽  
David Coombes ◽  
Salim Ismail ◽  
Craig Billington ◽  
Renwick CJ Dobson

Bacteriophage endolysins degrade peptidoglycan and have been identified as antibacterial candidates to combat antimicrobial resistance. Considering the catalytic and structural diversity of endolysins, there is a paucity of structural data to inform how these enzymes work at the molecular level—key data that is needed to realize the potential of endolysin-based antibacterial agents. Here, we determine the atomic structure and define the enzymatic function of Escherichia coli O157:H7 phage FTEBc1 endolysin, LysT84. Bioinformatic analysis reveals that LysT84 is a modular endolysin, which is unusual for Gram-negative endolysins, comprising a peptidoglycan binding domain and an enzymatic domain. The crystal structure of LysT84 (2.99 Å) revealed a mostly α-helical protein with two domains connected by a linker region but packed together. LysT84 was determined to be a monomer in solution using analytical ultracentrifugation. Small-angle X-ray scattering data revealed that LysT84 is a flexible protein but does not have the expected bimodal P(r) function of a multidomain protein, suggesting that the domains of LysT84 pack closely creating a globular protein as seen in the crystal structure. Structural analysis reveals two key glutamate residues positioned on either side of the active site cavity; mutagenesis demonstrating these residues are critical for peptidoglycan degradation. Molecular dynamic simulations suggest that the enzymatically active domain is dynamic, allowing the appropriate positioning of these catalytic residues for hydrolysis of the β(1–4) bond. Overall, our study defines the structural basis for peptidoglycan degradation by LysT84 which supports rational engineering of related endolysins into effective antibacterial agents.

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12524
Elizabeth M. Antaki-Zukoski ◽  
Xunde Li ◽  
Bruce Hoar ◽  
John M. Adaska ◽  
Barbara A. Byrne ◽  

Background The presence of Escherichia coli O157:H7 (E. coli O157:H7) super-shedding cattle in feedlots has the potential to increase the overall number (bio-burden) of E. coli O157:H7 in the environment. It is important to identify factors to reduce the bio-burden of E. coli O157 in feedlots by clarifying practices associated with the occurrence of super-shedders in feedlot cattle. Methods The objective of this study is to (1) identify host, pathogen, and management risk factors associated with naturally infected feedlot cattle excreting high concentrations of E. coli O157:H7 in their feces and (2) to determine whether the ingested dose or the specific strain of E. coli O157:H7 influences a super-shedder infection within experimentally inoculated feedlot cattle. To address this, (1) pen floor fecal samples and herd parameters were collected from four feedlots over a 9-month period, then (2) 6 strains of E. coli O157:H7, 3 strains isolated from normal shedder steers and 3 strains isolated from super-shedder steers, were inoculated into 30 one-year-old feedlot steers. Five steers were assigned to each E. coli O157:H7 strain group and inoculated with targeted numbers of 102, 104, 106, 108, and 1010 CFU of bacteria respectively. Results In the feedlots, prevalence of infection with E. coli O157:H7 for the 890 fecal samples collected was 22.4%, with individual pen prevalence ranging from 0% to 90% and individual feedlot prevalence ranging from 8.4% to 30.2%. Three samples had E. coli O157:H7 levels greater than 104 MPN/g feces, thereby meeting the definition of super-shedder. Lower body weight at entry to the feedlot and higher daily maximum ambient temperature were associated with increased odds of a sample testing positive for E. coli O157:H7. In the experimental inoculation trial, the duration and total environmental shedding load of E. coli O157:H7 suggests that the time post-inoculation and the dose of inoculated E. coli O157:H7 are important while the E. coli O157:H7 strain and shedding characteristic (normal or super-shedder) are not. Discussion Under the conditions of this experiment, super-shedding appears to be the result of cattle ingesting a high dose of any strain of E. coli O157:H7. Therefore strategies that minimize exposure to large numbers of E. coli O157:H7 should be beneficial against the super-shedding of E. coli O157:H7 in feedlots.

2021 ◽  
Vol 9 (3) ◽  
pp. 179-186
Devi Yanti Sari ◽  
Herwin Pisestyani ◽  
Denny Widaya Lukman

Kebab merupakan salah satu makanan siap saji atau ready to eat (RTE) yang populer di seluruh dunia. Escherichia coli (E. coli) O157:H7 banyak dihubungkan dengan kejadian outbreak foodborne disease pada kebab. Kontaminasi E. coli O157:H7 resistan antibiotik pada kebab dapat menimbulkan masalah kesehatan serius. Penelitian ini bertujuan mengidentifikasi E. coli O157:H7 resistan antibiotik yang diisolasi dari daging kebab yang dijual di sekitar Kampus IPB Dramaga Bogor. Total 43 sampel daging kebab diambil dari seluruh pedagang kebab di sekitar Kampus IPB Dramaga dalam radius 2 km dari batas terluar Kampus. Isolasi dan identifikasi E. coli mengacu pada Standar Nasional Indonesia (SNI) 2897:2008 dari Badan Standardisasi Nasional tentang Metode Pengujian Cemaran Mikroba dalam Daging, Telur, dan Susu, serta Hasil Olahannya. Uji serotyping E. coli O157:H7 menggunakan uji Serologis. Uji resistansi E. coli O157:H7 mengacu pada standar Clinical Laboratory Standards Institute (CLSI) dan dilakukan terhadap 10 jenis antibiotik menggunakan metode Kirby-Bauer disk diffusion. Data yang diperoleh dianalisis secara deskriptif. Hasil penelitian menunjukkan enam isolat positif E. coli O157:H7 (31.6%; 6/19) yang resistan terhadap ampisilin, amoksisilin-asam klavulanat, sefotaksim, gentamisin, siprofloksasin, enrofloksasin, kolistin sulfat dengan satu isolat termasuk multidrug resistant (MDR). Semua isolat E. coli O157:H7 masih sensitif terhadap trimethoprim-sulfametoksasol, oksitetrasiklin, dan kloramfenikol.

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