Enterohemorrhagic Research Articles

The microbiological quality of flour products in the UK with respect to Salmonella and Shiga-toxin-producing E. coli (STEC).

To investigate the possible contamination of raw flour and raw flour-based products, such as pancake/batter mixes, with Salmonella, generic E. coli and STEC. Samples included flours available for sale in the UK over a period of four months (January to April 2020). The Bread and Flour regulations, 1998 state the permitted ingredients in flour and bread but it does not specify the regular monitoring of the microbiological quality of flour and flour-based products. Samples of raw flour were collected by local authority sampling officers in accordance with current guidance on microbiological food sampling then transported to the laboratory for examination. Microbiological testing was performed to detect Salmonella spp., generic E. coli and Shiga-toxin-producing Escherichia coli (STEC) characterised for the presence of STEC virulence genes: stx1, stx2 and subtypes, eae, ipah, aggR, lt, sth and stp, using molecular methods (PCR). Of the 882 flours sampled, the incidence of Salmonella was 0.1% (a single positive sample that contained multiple ingredients such as flour, dried egg and dried milk, milled in the UK), and 68 samples (7.7%) contained generic E. coli at a level of >20 CFU/g. Molecular characterisation of flour samples revealed the presence of the Shiga-toxin (stx) gene in 10 samples (5 imported and 5 from the UK) (1.1%), from which STEC was isolated from 7 samples (0.8%). Salmonella and STEC isolates were sequenced to provide further characterisation of genotypes and to compare to sequences of human clinical isolates held in the UKHSA archive. Using our interpretive criteria based on genetic similarity, none of the STEC flour isolates correlated with previously observed human cases, while the singular Salmonella serotype Newport isolate from the mixed ingredient product was similar to a human case in 2019, from the UK, of S. Newport. Although there have been no reported human cases of STEC matching the isolates from these flour samples, some of the same serotypes and stx subtypes detected are known to have caused illness in other contexts. Results indicate that while the incidence was low, there is a potential for the presence of Salmonella and STEC in flour, and a genetic link was demonstrated between a Salmonella isolate from a flour-based product and a human case of salmonellosis.

A challenging STEC strain isolation from patients' stools: an O166:H15 STEC strain with the stx2 gene.

Shiga toxin-producing E. coli (STEC) infections can lead to severe complications such as bloody diarrhea and hemolytic uremic syndrome (HUS), especially in young children and the elderly. Strains that carry the shiga toxin 2 gene (stx2), such as O157:H7, have been mostly linked with severe disease outcomes. In recent years, outbreaks caused by non-O157:H7 strains have increased. E. coli O166:H15 has been previously reported causing a gastroenteritis outbreak in 1996 as a non-STEC strain, however the O166:H15 serotype we recovered carried the stx2 gene. It was particularly challenging to isolate this strain from stools by culture. Consequently, we tested immunomagnetic separation for the STEC recovery, which was a novel approach on clinical stools. Virulence genes were included for the characterization of these isolates.

Vacation in Egypt associated with Shiga toxin-producing Escherichia coli infection in children and adolescents, northern Italy, 2023.

BackgroundHaemolytic uremic syndrome (HUS) is a severe complication of infection with Shiga toxin-producing Escherichia coli (STEC). Although the reservoirs of STEC are known, the source of the infection of sporadic cases is often unknown. In 2023, we observed several cases of bloody diarrhoea with STEC infection in children and adolescents returning from vacations.AimWe aimed to explore the association between travel and bloody diarrhoea with STEC infection in children and adolescents.MethodsWe included all children and adolescents with bloody diarrhoea with STEC infection identified in 2023 by the ItalKid-HUS Network surveillance system in northern Italy. We interviewed children's families and sent a questionnaire on recent travels abroad. The exposure time was between 3 days after arrival abroad and 5 days after return home. A self-controlled case series (SCCS) design was used in the analysis.ResultsOf the 43 cases, 11 developed HUS. Twenty-three cases did not travel abroad, while 20 had travelled to several destinations. The incidence rate ratio (IRR) associated with travel to Egypt was 88.6 (95% confidence interval (CI): 17.0-462). Serotype analysis excluded the possibility of a single strain causing the infections. We did not find the source of the infections.ConclusionThere is an elevated risk of acquiring STEC infection with bloody diarrhoea and HUS associated with travel to Egypt. Specific investigations to identify the source are needed to implement effective preventive measures.

Evaluation of the Humoral Response after Immunization with a Chimeric Subunit Vaccine against Shiga Toxin-Producing Escherichia coli in Pregnant Sows and Their Offspring.

Shiga toxin-producing Escherichia coli (STEC) poses a significant public health risk due to its zoonotic potential and association with severe human diseases, such as hemorrhagic colitis and hemolytic uremic syndrome. Ruminants are recognized as primary reservoirs for STEC, but swine also contribute to the epidemiology of this pathogen, highlighting the need for effective prevention strategies across species. Notably, a subgroup of STEC that produces Shiga toxin type 2e (Stx2e) causes edema disease (ED) in newborn piglets, economically affecting pig production. This study evaluates the immunogenicity of a chimeric protein-based vaccine candidate against STEC in pregnant sows and the subsequent transfer of immunity to their offspring. This vaccine candidate, which includes chimeric proteins displaying selected epitopes from the proteins Cah, OmpT, and Hes, was previously proven to be immunogenic in pregnant cows. Our analysis revealed a broad diversity of STEC serotypes within swine populations, with the cah and ompT genes being prevalent, validating them as suitable antigens for vaccine development. Although the hes gene was detected less frequently, the presence of at least one of these three genes in a significant proportion of STEC suggests the potential of this vaccine to target a wide range of strains. The vaccination of pregnant sows led to an increase in specific IgG and IgA antibodies against the chimeric proteins, indicating successful immunization. Additionally, our results demonstrated the effective passive transfer of maternal antibodies to piglets, providing them with immediate, albeit temporary, humoral immunity against STEC. These humoral responses demonstrate the immunogenicity of the vaccine candidate and are preliminary indicators of its potential efficacy. However, further research is needed to conclusively evaluate its impact on STEC colonization and shedding. This study highlights the potential of maternal vaccination to protect piglets from ED and contributes to the development of vaccination strategies to reduce the prevalence of STEC in various animal reservoirs.

Prevalence, Molecular Characterization, and Antimicrobial Resistance Profiles of Shiga Toxin-Producing Escherichia coli Isolated from Raw Beef, Pork, and Chicken Meat in Vietnam.

Shiga toxin-producing Escherichia coli (STEC) is one of the most important foodborne pathogens, and the rise of antibiotic resistance to it is a significant threat to global public health. The purpose of this study is to investigate the prevalence, molecular characterization, and antibiotic resistance of STEC isolated from raw meat in Vietnam. The findings in this study showed that the prevalence of STEC in raw beef, pork, and chicken meat was 9.72% (7/72), 5.56% (4/72), and 1.39% (1/72), respectively. The STEC isolates were highly resistant to ampicillin (91.67%) and tetracycline (91.67%), followed by trimethoprim/sulfamethoxazole (83.33%), streptomycin (75%), and florfenicol (66.67%). The incidence of STEC virulence-associated genes, including stx1, stx2, eae, and ehxA, was 8.33% (1/12), 91.67% (11/12), 33.33% (4/12), and 58.33% (7/12), respectively. STEC serogroups O157, O26, and O111 were detected in 3 out of 12 STEC isolates. Two isolates were found to be ESBL producers carrying the blaCTX-M-55 gene, and three isolates were colistin-resistant strains harboring the mcr-1 gene. Notably, a STEC O111 isolate from chicken meat harbored both the blaCTX-M-55 and mcr-1 genes.

Impact of Western Diet on Enterohemorrhagic Escherichia coli Colonization in the Human In Vitro Mucosal Artificial Colon as Mediated by Gut Microbiota.

Enterohemorrhagic Escherichia coli (EHEC) is a major food-borne pathogen that causes human disease ranging from diarrhea to life-threatening complications. Accumulating evidence demonstrates that the Western diet enhances the susceptibility to enteric infection in mice, but the effect of diet on EHEC colonization and the role of human gut microbiota remains unknown. Our research aimed to investigate the effects of a Standard versus a Western diet on EHEC colonization in the human in vitro Mucosal ARtificial COLon (M-ARCOL) and the associated changes in the gut microbiota composition and activities. After donor selection using simplified fecal batch experiments, two M-ARCOL bioreactors were inoculated with a human fecal sample (n = 4) and were run in parallel, one receiving a Standard diet, the other a Western diet and infected with EHEC O157:H7 strain EDL933. EHEC colonization was dependent on the donor and diet in the luminal samples, but was maintained in the mucosal compartment without elimination, suggesting a favorable niche for the pathogen, and may act as a reservoir. The Western diet also impacted the bacterial short-chain fatty acid and bile acid profiles, with a possible link between high butyrate concentrations and prolonged EHEC colonization. The work demonstrates the application of a complex in vitro model to provide insights into diet, microbiota, and pathogen interactions in the human gut.

Antibacterial activity of t-cinnamaldehyde: An approach to its mechanistic principle towards enterohemorrhagic Escherichia coli (EHEC)

BackgroundCompounds of natural origin are potent source of drugs with unique mechanisms of action. Among phytochemicals, trans-cinnamaldehyde (t-CA) exhibits a wide range of biological activity, thus has been used for centuries to fight bacterial and fungal infections. However, the molecular basis of these properties has not been fully covered. Considering that difficult-to-control infections are becoming a rising global problem, there is a need to elucidate the molecular potential of t-CA. PurposeTo evaluate the antibacterial activity of t-CA against Shiga-toxigenic E. coli strains and elucidate its mechanism of action based on the inhibition of the virulence factor expression. MethodsThe antimicrobial potential of t-CA was assessed with two-fold microdilution and time-kill assays. Further evaluation included bioluminescence suppression assays, quantification of reactive oxygen species (ROS) and assessment of NAD+/NADH ratios. Morphological changes post t-CA exposure were examined using transmission electron microscopy. RNA sequencing and radiolabeling of nucleotides elucidated the metabolic alterations induced by t-CA. Toxin expression level was monitored through the application of fusion proteins, monitoring of bacteriophage development, and fluorescence microscopy studies. Lastly, the therapeutic efficacy in vivo was assessed using Galleria mellonella infection model. ResultsA comprehensive study of t-CA's bioactivity showed unique properties affecting bacterial metabolism and morphology, resulting in significant bacterial cell deformation and effective virulence inhibition. Elucidation of the underlying mechanisms indicated that t-CA activates the global regulatory system, the stringent response, manifested by its alarmone, (p)ppGpp, overproduction mediated by the RelA enzyme, thereby inhibiting bacterial proliferation. Intriguingly, t-CA effectively downregulates Shiga toxin gene expression via alarmone molecules, indicating its potential for therapeutic effect. In vivo validation demonstrated a significant improvement in larval survival rates post- t-CA treatment with 50 mg/kg (p < 0.05), akin to the efficacy observed with azithromycin, thus indicating its effectiveness against EHEC infections (p < 0.05). ConclusionsCollectively, these results reveal the robust antibacterial capabilities of t-CA, warranting its further exploration as a viable anti-infective agent.

How to Improve Surveillance Program for Shiga Toxin-Producing E. coli (STEC): Gap Analysis and Pilot Study.

Several pathotypes of enteric E. coli have been identified. The group represented by Shiga toxin-producing E. coli (STEC) is of particular interest. Raw milk and raw milk products are significant sources of STEC infection in humans; therefore, identifying pathogens at the herd level is crucial for public health. Most national surveillance programs focus solely on raw milk and raw milk cheeses that are ready for retail sale, neglecting the possibility of evaluating the source of contamination directly at the beginning of the dairy chain. To assess the viability of the application of new molecular methodologies to STEC identification in raw milk filters and in calf feces, we analyzed 290 samples from 18 different dairy herds, including 88 bulk tank milk (BTM), 104 raw milk filters (RMF), and 98 calf feces samples. In total 3.4% of BTM, 41.4% of RMF, and 73.4% of calves' feces were positive for stx, supporting our hypothesis that BTM is not a suitable matrix to assess the presence of STEC at herd level, underestimating it. Our conclusion is that the surveillance program needs critical and extensive improvements such as RMF and calves' feces analysis implementation to be more efficient in detecting and preventing STEC infections. The epidemiology of these infections and the characteristics of the pathogen clearly show how a One Health approach will be pivotal in improving our capabilities to control the spread of these infections.

Virulent-MDR-ESBL E. coli and Klebsiella pneumoniae report from North Sinai calves diarrhea and in vitro antimicrobial by Moringa oleifera

The health of calves has a significant impact on the production of cows and livestock. Some desert plants have pharmacological importance, as they can be used to reduce antibiotic resistance. Our hypothesis is designed to detect Virulent- Multidrug-Resistant and Extended- spectrum Beta- lactamase Enterobacteriaceae (Virulent-MDR-ESBL Enterobacteriaceae and to determine whether Moringa oleifera has antibacterial activity against the detected isolates. A total of 39 Enterobacteriaceae isolates from 28 diarrheic samples were collected from calves aged between 20 days and 20 months from 3 different flocks in North Sinai, Sahl-Eltina region, Egypt. E.coli 46% (18/39), O157 13% (5/39), Klebsiella pneumoniae 41% (16/39). MDR members accounted for 87%, while ESBL isolates accounted for 43%. The antibacterial activity is represented by microdilution. Minimum inhibition concentration (MIC) for the methanol extract of Moringa oleifera ranged from 2.5,5,10, and 25mg/ ml among E.coli isolates, and O157 was susceptible to (2.5mg/ ml), Klebsiella pneumoniae isolates were susceptible to (5-50mg/ ml). Analysis of the methanol extract revealed that ferulic acid was the dominant phenolic compound with a concentration of 29,832 parts per million (ppm). In silico docking study expected the active site of ferulic acid to act on the tyrosine bacterial enzyme through Pi-alkyl, Pi-anion, Carbon hydrogen bonds, and extra ionic attractive interactions with copper ions which can stabilize ferulic acid inside the targeted pocket Diverse virulent gene profiles were observed in E. coli. The Shiga toxin-producing Escherichia coli (STEC) was reported in 83% of the isolated E. coli, while the DNA gyrase (gyrA) was harbored in 100% of Klebsiella pneumoniae isolates. Various profiles of antibiotic resistance genes for both E. coli and Klebsiella pneumoniae isolates were distinguished. blaTEM genes were detected in 99% of E. coli and 100% of Klebsiella pneumoniae. Sequence analysis for E. coli strain DRC-North Sinai-Eg was placed in accession numbers (OP955786) for the Shiga toxin 2 gene (Stx2A), (OP997748) and (OP997749) for the Adhesion to host cell gene (Eae). For the hemolysine gene (hylA), the accession number was (OP946183). Klebsiellapneumoniae strain DRC-North Sinai-Eg was placed in (OP946180) for (gyrA). This study has proven the broad range of Moringa oliefera's antibacterial effects in vitro against the virulent-MDR- ESBL E. coli and Klebsiella pneumoniae isolated from North Sinai calves diarrhea. These are congruent with the disability effect on bacterial tyrosinase enzyme through docking study therefore, we recommend the usage of this desert plant as a prospective feed additive, we endorse this as an antibacterial new insight natural source and for the medication of considered pathogens with zoonotic impacts.Graphical

The effects of dielectric barrier discharge cold plasma on the safety and shelf life parameters of mozzarella cheese

The current study aimed to evaluate the effect of dielectric barrier discharge cold atmospheric plasma (DBD-CAP) on mozzarella cheese during 9 days of storage at 4 °C. The effect of DBD-CAP at 75 kV at three different treatment times (1, 3, and 5 min) on enterohemorrhagic Escherichia coli (EHEC), microbiological, physical, rheological, and sensory characteristics was analyzed. Moreover, DBD-CAP effects on composition, physicochemical, texture, rheology, meltability, oiling-off, sensory, and shelf life were evaluated. Our results showed that DBD-CAP at 3 and 5 min treatment time removed EHEC while reducing the total microbiota, Pseudomonas, Enterobacteriaceae, mesophilic bacteria, and yeasts. Moreover, DBD-CAP maintained the treated mozzarella samples' moisture, fat content, pH, and protein content. However, 3 min mozzarella treatment maintained color, odor, and taste quality compared to the control due to reduced yeast growth. Shelf life evaluation revealed that 3 min DBD-CAP treatment extended the shelf life of mozzarella cheese by at least two days; therefore, DBD-CAP can be effectively used to extend the shelf life of mozzarella without apparent side effects.

Shiga toxin-producing Escherichia coli O157:H7 outbreak associated with school field trips at a farm animal exhibit-Tennessee, September-October 2023.

In October 2023, the Tennessee Department of Health identified an outbreak of Shiga toxin-producing Escherichia coli (STEC) O157:H7 infections among elementary school students who attended school field trips to the same farm animal exhibit. Our aim was to determine STEC source and prevent additional illnesses by initiating epidemiologic, laboratory and environmental investigations. We identified cases using laboratory-based surveillance and by surveying caregivers of children who attended the exhibit. Probable cases were defined as illness with abdominal cramps or diarrhoea after attendance; confirmed cases were laboratory-confirmed STEC infection in an attendee or household contact. A site visit was conducted, and event organizers were interviewed. Human stool, animal faeces and environmental samples were tested for STEC O157:H7 by real-time polymerase chain reaction (PCR), culture and whole-genome sequencing (WGS). Approximately 2300 elementary school students attended the animal exhibit during 2 days. Field trip activities included contact with different farm animal species, drinking pasteurized milk outside animal enclosures and eating lunch in a separate building onsite. We received survey responses from 399 caregivers for 443 (19%) animal exhibit attendees. We identified 9 confirmed and 55 probable cases with illness onset dates during 26 September to 12 October. Seven children aged 1-7 years were hospitalized. Four children aged 1-6 years experienced haemolytic uraemic syndrome; none died. Laboratory testing identified STEC O157:H7 by culture from eight human stool samples with 0-1 allele difference by WGS. Three environmental samples had Shiga toxin (stx 2) genes detected by PCR, but no STEC isolates were recovered by culture. This is the largest reported STEC O157:H7 outbreak associated with an animal exhibit in Tennessee. We identified opportunities for educating school staff, event organizers and families about zoonotic disease risks associated with animal contact and published prevention measures.

One problem, multiple potential targets: Where are we now in the development of small molecule inhibitors against Shiga toxin?

Shiga toxin-producing Escherichia coli (STEC) are a group of enteric pathogens which carry phage-encoded Shiga toxins (Stx). STEC infections begin with severe abdominal pain and non-bloody diarrhoea, which can progress to bloody diarrhoea after approximately 4-days post-infection. In high-risk groups such as children and the elderly, patients may develop haemolytic uremic syndrome (HUS). HUS is characterised by microangiopathic haemolytic anaemia, thrombocytopenia, and in severe disease acute renal failure. Traditional antibiotics have been linked with increased toxin production due to the activation of recA-mediated bacterial stress response, resulting in poorer patient outcomes. Therefore, treatment relies on supportive therapies. Antivirulence strategies have been explored as an alternative treatment for bacterial infections and blockers of virulence factors such as the Type III Secretion System. Recent improvements in the mechanistic understanding of the Stx pathway have led to the design of inhibitors to disrupt the pathway, leading to toxin-mediated ribosome damage. However, compounds have yet to progress beyond Phase III clinical trials successfully. This review explores the progress in developing small molecule inhibitors by collating lead compounds derived from in-silico and experimental approaches.

Modeling the growth/no growth response of Non-O157 Shiga toxin-producing Escherichia coli to temperature, pH and water activity

The objective of this study was to model the effect of temperature, pH and water activity (aw) on the growth/no growth response of non-O157 Shiga toxin-producing E. coli (STEC). A cocktail of six-serogroup STEC was inoculated into brain heart infusion broth (BHI) with 48 combinations of different pH and aw, and the inoculated medium was incubated at one of ten temperatures. After 62 days of incubation, growth was determined by turbidity and plating on tryptic soy agar. Binary data (0 [no growth] or 1 [growth]) were fitted into a nonlinear logistic regression and the parameters were estimated. The model was validated with independently produced data from seven serogroups of non-O157 STEC, a cocktail of E. coli O157:H7, and two panels of six-serogroup of STEC. The non-O157 STEC did not grow at temperatures ≤6 °C and ≥47 °C, and the highest tolerance to pH and aw occurred at 25 °C. Although slight difference in the growth/no growth response was observed among different groups of STEC, the developed model can be applied to all the STECs with an average concordance of 92.3%. This work provides valuable insight into the growth/no-growth response of STEC under various environmental conditions.

Rapid and visual detection of Shiga-toxigenic Escherichia coli (STEC) in carabeef meat harnessing loop-mediated isothermal amplification (LAMP).

Shiga toxigenic E. coli are important foodborne zoonotic pathogens. The present study was envisaged to standardize loop-mediated isothermal amplification assays targeting stx1 and stx2 genes for rapid and visual detection of STEC and compare its sensitivity with PCR. The study also assessed the effect of short enrichment on the detection limit of LAMP and PCR. The developed LAMP assays were found to be highly specific. Analytical sensitivity of LAMP was 94fg/µLand 25.8fg/µL for stx-1 and stx-2 while LOD of 5 CFU/g of carabeef was measured after 6-12h enrichment. The study highlights the importance of short (6-12h) enrichment for improving the sensitivity of LAMP. The entire detection protocol could be performed within 9h yielding results on the same day. The developed LAMP assays proved to be a handy and cost-effective alternative for screening STEC contamination in meat.

Prevalence and antimicrobial resistance patterns of diarrheagenic and uropathogenic Escherichia coli in Odisha, India

Objective: The aim of this study was to determine the prevalence and antibiotic susceptibility patterns of pathogenic Escherichia (E.) coli causing diarrhea and urinary tract infection (UTI) in patients admitted for treatment in selected health care facilities in Odisha, an eastern Indian State. Methods: A total of 189 rectal swabs from patients with diarrhea and 297 urine samples from patients with UTI were collected from selected health care facilities. E. coli isolates were phenotypically confirmed using MacConkey agar, MacConkey sorbitol agar and blood agar along with biochemical tests. These phenotypically confirmed E. coli isolates were investigated genotypically for known pathogenic E. coli via multiplex PCR. Finally, the pathogenic E. coli was subjected to antibiotic sensitivity test. Results: Culture of 189 rectal swabs and 297 urine samples revealed 46 (24.3%) diarrheagenic E. coli (DEC) and 36 (12.1%) uropathogenic E. coli (UPEC). PCR analysis of DEC identified 27 (14.3%) enterotoxigenic E. coli (ETEC), 8 (4.2%) enteropathogenic E. coli, 10 (5.3%) enteroaggregative E. coli and 1 (0.5%) Enterohemorrhagic E. coli (EHEC) in diarrhea patients and 5 (1.7%) ETEC, 7 (2.4%) enteroaggregative E. coli, 11 (3.7%) EHEC O157:H7 and 1 (0.3%) EHEC non-O157:H7 in UTI patients. DEC and UPEC exhibited multidrug resistance with a high rate of resistance to commonly prescribed antibiotics. A high frequency of ETEC causing diarrhea, atypical enteropathogenic E. coli harboring the eae gene was found among children with acute diarrhea, and ETEC (est+ ) and EHEC O157:H7 were detected in UTI patients along with high antibiotic resistance among DEC and UPEC were important findings. Conclusions: To the best of our knowledge, this is the first study to report the prevalence of DEC and UPEC in patients admitted to hospital in Odisha, India, revealing a high rate of antimicrobial resistance.

Anatural approach tocombating antibiotic-resistant pathogens inlivestock: Hibiscus sabdariffa-derived hibiscus acid asapromising solution.

Weexamined the antibacterial efficacy ofstreptomycin, hibiscus acid, and their combination against multidrug-resistant Shiga-toxin-producing Escherichia coli (STEC) and Salmonella Typhimurium inmice. Wedetermined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for streptomycin, hibiscus acid, and their combination against STEC and Salmonella. Fifteen sets ofsix mice ineach set were utilised: six groups were orally exposed to4log10 colony forming units (CFUs) ofS.Typhimurium and another six toSTEC, and three acted asthe controls. Six hours post-inoculation, specific groups ofmice received either oral solutions containing hibiscus acid at5 and 7mg/ml; streptomycin at50 and 450μg/ml; hibiscus acid/streptomycin (5mg/ml hibiscus acid and 50μg/ml streptomycin); orisotonic saline. The study determined the MIC and MBC of7mg/ml ofhibiscus acid; 300 and 450μg/ml ofstreptomycin; and two concentrations ofhibiscus/streptomycin (3mg/ml/ 20μg/ml and 5mg/ml/ 50μg/ml). Interestingly, the mice that were infected and subsequently treated with hibiscus acid at7mg/ml alone orin conjunction with streptomycin did not have either STEC orSalmonella intheir faecal samples, and none ofthe mice died. Incontrast, the untreated mice and those exclusively treated with streptomycin had the pathogens present intheir stool, leading tothe mortality ofall the subjects.

FdeC expression regulates motility and adhesion of the avian pathogenic Escherichia coli strain IMT5155

Adaptation of avian pathogenic E. coli (APEC) to changing host environments including virulence factors expression is vital for disease progression. FdeC is an autotransporter adhesin that plays a role in uropathogenic Escherichia coli (UPEC) adhesion to epithelial cells. Expression of fdeC is known to be regulated by environmental conditions in UPEC and Shiga toxin-producing E. coli (STEC). The observation in a previous study that an APEC strain IMT5155 in which the fdeC gene was disrupted by a transposon insertion resulted in elevated adhesion to chicken intestinal cells prompted us to further explore the role of fdeC in infection. We found that the fdeC gene prevalence and FdeC variant prevalence differed between APEC and nonpathogenic E. coli genomes. Expression of the fdeC gene was induced at host body temperature, an infection relevant condition. Disruption of fdeC resulted in greater adhesion to CHIC-8E11 cells and increased motility at 42 °C compared to wild type (WT) and higher expression of multiple transporter proteins that increased inorganic ion export. Increased motility may be related to increased inorganic ion export since this resulted in downregulation of YbjN, a protein known to supress motility. Inactivation of fdeC in APEC strain IMT5155 resulted in a weaker immune response in chickens compared to WT in experimental infections. Our findings suggest that FdeC is upregulated in the host and contributes to interactions with the host by down-modulating motility during colonization. A thorough understanding of the regulation and function of FdeC could provide novel insights into E. coli pathogenesis.

Determinants of Sporadic Shiga Toxin-Producing Escherichia coli (STEC) Infection in Denmark, 2018-2020: A Matched Case-Control Study.

Infections with Shiga toxin-producing Escherichia coli (STEC) are increasing in Denmark and elsewhere. STEC is also the most frequent cause of haemolytic uraemic syndrome (HUS) in Danish children. Most cases are considered sporadic, while approximately one-third can be attributed to a known source of infection. Hence, we examined sources of sporadic STEC infection in Denmark. From January 2018 to December 2020, we conducted a prospective nationwide case-control study among Danish adults and children. Cases with confirmed positive STEC infection were notified infections within the national laboratory surveillance system. Control persons were randomly selected from the Danish Civil Registration System, individually matched in age in 5-year bands and sex. Participants were invited by an electronic letter to complete either an adult or child questionnaire online. Univariate and adjusted matched odds ratios were computed for adults and children using conditional logistic regression. The study recruited 1583 STEC cases and 6228 controls. A total of 658 cases (42%) and 2155 controls (35%) were included in the analysis. Depending on age, univariate analysis adjusted for socio-demographic determinants showed that the consumption of boiled beef (mOR = 2.2, 95% confidence interval (CI): 1.6-3.1) and fried minced beef (mOR = 1.6, CI: 1.2-2.1), drinking raw (unpasteurized) milk (mOR = 11, CI 1.1-110), eating grilled food (mOR = 9.8, CI: 5.6-17) and having a household member using diapers (mOR = 2.1, CI: 1.4-3.2) were determinants of sporadic STEC infection. Further multivariate adjusted analysis resulted in the same determinants. This study confirms that beef is an overall important risk factor for STEC infection in Denmark. We also present evidence that a proportion of sporadic STEC infections in Denmark are determined by age-specific eating habits, environmental exposures and household structure, rather than being exclusively food-related. These findings are relevant for targeted public health actions and guidelines.

Metabolism of l-arabinose converges with virulence regulation to promote enteric pathogen fitness

Virulence and metabolism are often interlinked to control the expression of essential colonisation factors in response to host-associated signals. Here, we identified an uncharacterised transporter of the dietary monosaccharide ʟ-arabinose that is widely encoded by the zoonotic pathogen enterohaemorrhagic Escherichia coli (EHEC), required for full competitive fitness in the mouse gut and highly expressed during human infection. Discovery of this transporter suggested that EHEC strains have an enhanced ability to scavenge ʟ-arabinose and therefore prompted us to investigate the impact of this nutrient on pathogenesis. Accordingly, we discovered that ʟ-arabinose enhances expression of the EHEC type 3 secretion system, increasing its ability to colonise host cells, and that the underlying mechanism is dependent on products of its catabolism rather than the sensing of ʟ-arabinose as a signal. Furthermore, using the murine pathogen Citrobacter rodentium, we show that ʟ-arabinose metabolism provides a fitness benefit during infection via virulence factor regulation, as opposed to supporting pathogen growth. Finally, we show that this mechanism is not restricted to ʟ-arabinose and extends to other pentose sugars with a similar metabolic fate. This work highlights the importance integrating central metabolism with virulence regulation in order to maximise competitive fitness of enteric pathogens within the host-niche.

Transcriptomic and proteomic analysis of the virulence inducing effect of ciprofloxacin on enterohemorrhagic Escherichia coli.

Enterohemorrhagic E. coli (EHEC) is considered to be the most dangerous pathotype of E. coli, as it causes severe conditions such as hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS). Antibiotic treatment of EHEC infections is generally not recommended since it may promote the production of the Shiga toxin (Stx) and lead to worsened symptoms. This study explores how exposure to the fluoroquinolone ciprofloxacin reorganizes the transcriptome and proteome of EHEC O157:H7 strain EDL933, with special emphasis on virulence-associated factors. As expected, exposure to ciprofloxacin caused an extensive upregulation of SOS-response- and Stx-phage proteins, including Stx. A range of other virulence-associated factors were also upregulated, including many genes encoded by the LEE-pathogenicity island, the enterohemolysin gene (ehxA), as well as several genes and proteins involved in LPS production. However, a large proportion of the genes and proteins (17 and 8%, respectively) whose expression was upregulated upon ciprofloxacin exposure (17 and 8%, respectively) are not functionally assigned. This indicates a knowledge gap in our understanding of mechanisms involved in EHECs response to antibiotic-induced stress. Altogether, the results contribute to better understanding of how exposure to ciprofloxacin influences the virulome of EHEC and generates a knowledge base for further studies on how EHEC responds to antibiotic-induced stress. A deeper understanding on how EHEC responds to antibiotics will facilitate development of novel and safer treatments for EHEC infections.