A multi-epitope fusion antigen candidate vaccine for Enterotoxigenic Escherichia coli is protective against strain B7A colonization in a rabbit model

Enterotoxigenic Escherichia coli (ETEC) strains are a leading cause of children's and travelers' diarrhea. Developing effective vaccines against this heterologous group has proven difficult due to the varied nature of toxins and adhesins that determine their pathology. A multivalent candidate vaccine was developed using a multi-epitope fusion antigen (MEFA) vaccinology platform and shown to effectively elicit broad protective antibody responses in mice and pigs. However, direct protection against ETEC colonization of the small intestine was not measured in these systems. Colonization of ETEC strains is known to be a determining factor in disease outcomes and is adhesin-dependent. In this study, we developed a non-surgical rabbit colonization model to study immune protection against ETEC colonization in rabbits. We tested the ability for the MEFA-based vaccine adhesin antigen, in combination with dmLT adjuvant, to induce broad immune responses and to protect from ETEC colonization of the rabbit small intestine. Our results indicate that the candidate vaccine MEFA antigen elicits antibodies in rabbits that react to seven adhesins included in its construction and protects against colonization of a challenge strain that consistently colonized naïve rabbits.

Characterization of Glycosylation-Specific Systemic and Mucosal IgA Antibody Responses to Escherichia coli Mucinase YghJ (SslE)

Efforts to develop broadly protective vaccines against pathogenic Escherichia coli are ongoing. A potential antigen candidate for vaccine development is the metalloprotease YghJ, or SslE. YghJ is a conserved mucinase that is immunogenic, heavily glycosylated, and produced by most pathogenic E. coli. To develop efficacious YghJ-based vaccines, there is a need to investigate to what extent potentially protective antibody responses target glycosylated epitopes in YghJ and to describe variations in the quality of YghJ glycosylation in the E. coli population. In this study we estimated the proportion of anti-YghJ IgA antibodies that targeted glycosylated epitopes in serum and intestinal lavage samples from 21 volunteers experimentally infected with wild-type enterotoxigenic E. coli (ETEC) strain TW10722. Glycosylated and non-glycosylated YghJ was expressed, purified, and then gycosylation pattern was verified by BEMAP analysis. Then we used a multiplex bead flow cytometric assay to analyse samples from before and 10 days after TW10722 was ingested. We found that 20 (95%) of the 21 volunteers had IgA antibody responses to homologous, glycosylated YghJ, with a median fold increase in IgA levels of 7.9 (interquartile range [IQR]: 7.1, 11.1) in serum and 3.7 (IQR: 2.1, 10.7) in lavage. The median proportion of anti-YghJ IgA response that specifically targeted glycosylated epitopes was 0.45 (IQR: 0.30, 0.59) in serum and 0.07 (IQR: 0.01, 0.22) in lavage. Our findings suggest that a substantial, but variable, proportion of the IgA antibody response to YghJ in serum during ETEC infection is targeted against glycosylated epitopes, but that gut IgA responses largely target non-glycosylated epitopes. Further research into IgA targeting glycosylated YghJ epitopes is of interest to the vaccine development efforts.

Structural Determination and Genetic Identification of the O-Antigen from an Escherichia coli Strain, LL004, Representing a Novel Serogroup

The O-antigen is the outermost component of the lipopolysaccharide layer in Gram-negative bacteria, and the variation of O-antigen structure provides the basis for bacterial serological diversity. Here, we determined the O-antigen structure of an Escherichia coli strain, LL004, which is totally different from all of the E. coli serogroups. The tetrasaccharide repeating unit was determined as →4)-β-d-Galp-(1→3)-β-d-GlcpNAc6OAc(~70%)-(1→3)-β-d-GalpA-(1→3)-β-d-GalpNAc-(1→ with monosaccharide analysis and NMR spectra. We also characterized the O-antigen gene cluster of LL004, and sequence analysis showed that it correlated well with the O-antigen structure. Deletion and complementation testing further confirmed its role in O-antigen biosynthesis, and indicated that the O-antigen of LL004 is assembled via the Wzx/Wzy dependent pathway. Our findings, in combination, suggest that LL004 should represent a novel serogroup of E. coli.

Method for the Detection of the Cleaved Form of Shiga Toxin 2a Added to Normal Human Serum

The pathogenesis of Escherichia coli-induced hemolytic uremic syndrome (eHUS) caused by infections with pathogenic Shiga toxin (Stx) producing E. coli (STEC) is centered on bacterial (e.g., Stx) and host factors (circulating cells, complement system, serum proteins) whose interaction is crucial for the immediate outcome and for the development of this life-threatening sequela. Stx2a, associated to circulating cells (early toxemia) or extracellular vesicles (late toxemia) in blood, is considered the main pathogenic factor in the development of eHUS. Recently, it was found that the functional properties of Stx2a (binding to circulating cells and complement components) change according to modifications of the structure of the toxin, i.e., after a single cleavage of the A subunit resulting in two fragments, A1 and A2, linked by a disulfide bridge. Herein, we describe a method to be used for the detection of the cleaved form of Stx2a in the serum of STEC-infected or eHUS patients. The method is based on the detection of the boosted inhibitory activity of the cleaved toxin, upon treatment with reducing agents, on a rabbit cell-free translation system reconstituted with human ribosomes. The method overcomes the technical problem caused by the presence of inhibitors of translation in human serum that have been stalled by the addition of RNAase blockers and by treatment with immobilized protein G. This method, allowing the detection of Stx2a at concentrations similar to those found by ELISA in the blood of STEC-infected patients, could be a useful tool to study the contribution of the cleaved form of Stx2a in the pathogenesis of eHUS.

Improving follow-up testing in children with Shiga toxin-producing Escherichia coli through provision of a provider information sheet

The aim of this study was to improve follow-up laboratory testing for children infected by Shiga toxin-producing Escherichia coli (STEC) through the provision of an information sheet to healthcare providers in the province of Alberta, Canada. An information sheet recommending the performance of laboratory tests, every 24-48h until 3 days after diarrhoea resolves or the platelet count stabilises or begins to rise, was sent to all physicians who ordered a STEC-positive stool test as of 1 November 2016. The information sheet was only distributed to physicians in one of the province's five healthcare delivery zones (i.e. intervention zone). Medical records for children aged <18 years with laboratory confirmed STEC-positive stool samples between November 2014 and November 2018 were reviewed to determine the performance of recommended laboratory tests. Post-intervention, follow-up testing in all categories increased significantly for cases that occurred in the intervention zone, with odds ratios (OR) ranging from 3.02 (95% CI: 1.35-6.78) to 3.94 (95% CI: 1.70-9.16) when compared with pre-intervention. No increase in any of the laboratory testing categories was detected outside of the intervention zone. The provision of a targeted information sheet to healthcare providers improved the monitoring of STEC-infected children.

Initial Immune Response in Escherichia coli, Staphylococcus aureus, and Candida albicans Bacteremia

Sepsis remains a leading cause of mortality worldwide and is characterized by sustained inflammatory responses, reflected as changes in the expression profile of cytokines with time. The aim of the present study was to investigate the dynamic changes in complete blood count, serum chemistry, procalcitonin (PCT), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) in Escherichia coli, Staphylococcus aureus, and Candida albicans bacteremia. Study subjects were 32 healthy male Landrace-Large White pigs, aged 10-15 weeks and of average weight 19 ± 2 kg. Bacteremia was induced by continuous intravenous infusion of microbial suspensions during a period of 8 h. E. coli and S. aureus bacteremia were associated with a significant gradual decrease in white blood cells and platelets, respectively (p = 0.002 and p = 0.004), while candidemia was characterized by a significant gradual decrease in lymphocytes (p = 0.009). Serum PCT levels were either undetectable or very low, with no significant changes with time in all groups. E. coli bacteremia elicited a strong pro-inflammatory response, characterized by a significant increase in TNF-α expression from the onset of bacteremia (p = 0.042). C. albicans exhibited a different profile with an early, moderate increase in TNF-α followed by a subsequent marked increase in IL-6 levels (p = 0.03). The differential regulation of inflammatory and hematological responses depending on the pathogenic agent can reveal differences in the underlying inflammatory mechanisms, which may assist in the ongoing quest for the identification of a panel of circulating biomarkers during bacteremia.

Use of serum amyloid A in serum and synovial fluid to detect eradication of infection in experimental septic arthritis in horses

While serum amyloid A (SAA) has been investigated as a potential marker for septic arthritis in horses, no study has reported on whether SAA can be used to detect eradication of joint infection. Therefore, the objective of this study was to investigate whether the eradication of joint infection in experimentally induced septic arthritis in horses can be detected using serum and synovial fluid SAA. A total of 17 horses were randomly assigned to 3 groups. A middle carpal joint of each horse was injected with saline (control group, n = 3), lipopolysaccharide (LPS) (nonseptic synovitis group, n = 6), or Escherichia coli (septic arthritis group, n = 8) on day 0. Starting on day 1, horses underwent treatment for septic arthritis. Sequential samples of serum and synovial fluid were collected, and quantification of SAA was carried out. Concentrations of serum and synovial fluid SAA were compared among groups and time points. A concurrent study was conducted and determined that infection was eradicated on day 4 in this experimental model of septic arthritis. Concentrations of serum and synovial fluid SAA rapidly increased after inoculation of E. coli and were highest on day 3 and day 4, respectively. Thereafter, both serum and synovial fluid SAA decreased with eradication of joint infection, although they remained significantly increased from baseline until day 9 and day 10, respectively. Serum and synovial fluid SAA did not increase in the control or nonseptic synovitis group. These findings suggest that serial measurements rather than a single measurement of SAA are required to determine eradication of infection from septic arthritis in horses.

Nonclonal Emergence of Colistin Resistance Associated with Mutations in the BasRS Two-Component System in Escherichia coli Bloodstream Isolates

Infections by multidrug-resistant Gram-negative bacteria are increasingly common, prompting the renewed interest in the use of colistin. Colistin specifically targets Gram-negative bacteria by interacting with the anionic lipid A moieties of lipopolysaccharides, leading to membrane destabilization and cell death. Here, we aimed to uncover the mechanisms of colistin resistance in nine colistin-resistant Escherichia coli strains and one Escherichia albertii strain. These were the only colistin-resistant strains of 1,140 bloodstream Escherichia isolates collected in a tertiary hospital over a 10-year period (2006 to 2015). Core-genome phylogenetic analysis showed that each patient was colonized by a unique strain, suggesting that colistin resistance was acquired independently in each strain. All colistin-resistant strains had lipid A that was modified with phosphoethanolamine. In addition, two E. coli strains had hepta-acylated lipid A species, containing an additional palmitate compared to the canonical hexa-acylated E. coli lipid A. One E. coli strain carried the mobile colistin resistance (mcr) gene mcr-1.1 on an IncX4-type plasmid. Through construction of chromosomal transgene integration mutants, we experimentally determined that mutations in basRS, encoding a two-component signal transduction system, contributed to colistin resistance in four strains. We confirmed these observations by reversing the mutations in basRS to the sequences found in reference strains, resulting in loss of colistin resistance. While the mcr genes have become a widely studied mechanism of colistin resistance in E. coli, sequence variation in basRS is another, potentially more prevalent but relatively underexplored, cause of colistin resistance in this important nosocomial pathogen.IMPORTANCE Multidrug resistance among Gram-negative bacteria has led to the use of colistin as a last-resort drug. The cationic colistin kills Gram-negative bacteria through electrostatic interaction with the anionic lipid A moiety of lipopolysaccharides. Due to increased use in clinical and agricultural settings, colistin resistance has recently started to emerge. In this study, we used a combination of whole-genome sequence analysis and experimental validation to characterize the mechanisms through which Escherichia coli strains from bloodstream infections can develop colistin resistance. We found no evidence of direct transfer of colistin-resistant isolates between patients. The lipid A of all isolates was modified by the addition of phosphoethanolamine. In four isolates, colistin resistance was experimentally verified to be caused by mutations in the basRS genes, encoding a two-component regulatory system. Our data show that chromosomal mutations are an important cause of colistin resistance among clinical E. coli isolates.

Pathogenic role of inflammatory response during Shiga toxin-associated hemolytic uremic syndrome (HUS)

Hemolytic uremic syndrome (HUS) is defined as a triad of noninmune microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. The most frequent presentation is secondary to Shiga toxin (Stx)-producing Escherichia coli (STEC) infections, which is termed postdiarrheal, epidemiologic or Stx-HUS, considering that Stx is the necessary etiological factor. After ingestion, STEC colonize the intestine and produce Stx, which translocates across the intestinal epithelium. Once Stx enters the bloodstream, it interacts with renal endothelial and epithelial cells, and leukocytes. This review summarizes the current evidence about the involvement of inflammatory components as central pathogenic factors that could determine outcome of STEC infections. Intestinal inflammation may favor epithelial leakage and subsequent passage of Stx to the systemic circulation. Vascular damage triggered by Stx promotes not only release of thrombin and increased fibrin concentration but also production of cytokines and chemokines by endothelial cells. Recent evidence from animal models and patients strongly indicate that several immune cells types may participate in HUS physiopathology: neutrophils, through release of proteases and reactive oxygen species (ROS); monocytes/macrophages through secretion of cytokines and chemokines. In addition, high levels of Bb factor and soluble C5b-9 (sC5b-9) in plasma as well as complement factors adhered to platelet-leukocyte complexes, microparticles and microvesicles, suggest activation of the alternative pathway of complement. Thus, acute immune response secondary to STEC infection, the Stx stimulatory effect on different immune cells, and inflammatory stimulus secondary to endothelial damage all together converge to define a strong inflammatory status that worsens Stx toxicity and disease.

Hyponatremia: a new predictor of mortality in patients with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome

OBJECTIVES

(1) Evaluate mortality rate in patients with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome, (2) determine the leading causes of death, and (3) identify predictors of mortality at hospital admission.

METHODS

We conducted a multicentric, observational, retrospective, cross-sectional study. It included patients under 18 years old with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome hospitalized between January 2005 and June 2016. Clinical and laboratory data were obtained from the Argentine National Epidemiological Surveillance System of Hemolytic Uremic Syndrome. Clinical and laboratory variables were compared between deceased and non-deceased patients. Univariate and multivariate analyses were performed. ROC curves and area under the curve were obtained.

RESULTS

Seventeen (3.65%) out of the 466 patients died, being central nervous system involvement the main cause of death. Predictors of death were central nervous system involvement, the number of days since the beginning of diarrhea to hospitalization, hyponatremia, high hemoglobin, high leukocyte counts, and low bicarbonate concentration on admission. In the multivariate analysis, central nervous system involvement, sodium concentration, and hemoglobin were independent predictors. The best cut off for sodium was ≤ 128 meq/l and for hemoglobin ≥ 10.8 g/dl.

CONCLUSIONS

Mortality was low in children with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome, being central nervous system involvement the main cause of death. The best mortality predictors found were central nervous system involvement, hemoglobin, and sodium concentration. Hyponatremia may be a new Shiga toxin-producing Escherichia coli hemolytic uremic syndrome mortality predictor.

Effect of Lactobacillus casei on serum interleukins following enteropathogenic E. coli infection in experimental rabbits

In the present study we investigated the pro-inflammatory and anti-inflammatory effect of Lactobacillus casei following infection with multi-drug resistant enteropathogenic Escherichia coli infection in experimental rabbits. For this purpose, 40 adult rabbits were divided into different groups and were infected with multi-drug resistant E. coli AZ1 strain except the control groups. The rabbits were orally administered with L. casei SABA6 strain in two different ways i.e. pre-treatment and post-treatment and both were continued for 7 days. The rabbits were sacrificed sequentially at 0, 4, 7 and 10 days post infection (dpi). Serum and intestinal tissue samples were collected from each rabbit. Intestinal tissue samples were subjected to histopathological examination that showed microscopic lesions at 4 and 7 dpi among infected group. The serum samples were processed for determination of Interleukin-6 (IL-6, pro-inflammatory) and Interleukin-10 (IL-10, anti-inflammatory) using ELISA. It was found that oral administration of L. casei SABA6 reduces the eruption of intestinal epithelial cells and reduces the incidence of diarrhea. Further, L. casei SABA6 also resulted in immuno modulation by significant increase in concentration of IL-6 and IL-10 particularly at 4 and 7 dpi and protects against E. coli AZ1 infection. Altogether, it was concluded that increased IL-6 and IL-10 levels were responsible for protection against EPEC infections. The sequential sacrifice of experimental animals could be adopted for future studies to find out pathogenesis and virulence mechanism of EPEC infections along with protective efficacy of different probiotics.

Extended-spectrum β-lactamase-producing E. coli septicemia among rectal carriers in the ICU

The aim of this study was to identify risk factors for extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E coli) bloodstream infection (BSI) among carriers hospitalized between March 2011 and June 2016 at the ICU of the West China Hospital.The cases were patients with at least 1 episode of ESBL-producing E coli BSI within 1 week after a positive rectal swab. Controls were selected randomly 1:2 among ESBL-producing E coli rectal carriers who did not develop BSI.Among 19,429 ICU patients, 9015 (46.4%) had a positive rectal swab for ESBL-producing E coli. Of them, 42 (0.5%) were diagnosed with ESBL-producing E coli BSI. The in-hospital mortality was higher for the BSI patients compared with controls (19.1% vs. 6.0%, P = .031). In the past 72 hours, patients in case group were more likely to use penicillin (odds ratio [OR] = 12.076; 95% confidence interval [CI]: 1.397-104.251, P = .02), cephalosporin (OR = 6.900; 95% CI: 1.493-31.852, P = .01), and carbapenem (OR = 5.422; 95% CI: 1.228-23.907, P = .03) as compared to patients in control group. Also, when compared to patients in control group, patients in case group were likely to stay for a longer time in ICU before positive rectal swab test (OR = 1.041, 95% CI: 1.009-1.075, P = .01) and have higher maximum body temperature before positive rectal swab (OR = 8.014; 95% CI: 2.408-26.620, P = .001).Bacteremia owing to ESBL-producing E coli was associated with high antimicrobial exposure, hospital stay, and maximum body temperature.

Effects of alpha-(1,2)-fucosyltransferase genotype variants on plasma metabolome, immune responses and gastrointestinal bacterial enumeration of pigs pre- and post-weaning

In pigs, the alpha-(1,2) fucosyltransferase (FUT1) gene has been highlighted for its properties in controlling the intestinal expression of enterotoxigenic E. coli (ETEC) F18 receptors; a pathogen causing edema disease and post-weaning diarrhoea. In this study, we hypothesized that pigs with different genotypes (ETEC F18 resistant (FUT1^AA) versus susceptible (FUT1^AG)) differed in following systemic and enteric responses: growth performance, plasma metabolic profiles, expression of candidate genes for intestinal mucosal homeostasis and immunity, number of selected bacteria and the concentration of short-chain fatty acids (SCFA) in faeces and digesta in piglets pre and post-weaning, and on the ETEC F18 adherence ex vivo. Genotype had the strongest impact on plasma metabolomic profile on day 7 and 28 of age. FUT1^AG piglets had higher level of N-methyl-2-pyrrolidinone, hippuric acid, oxindole, and 3-oxo-5-beta-chol-7-en-24-oic acid on day 7, and a higher level of guanosine on day 28 than that in the FUT1^AA piglets. FUT1^AA piglets had a higher level of betaine on day 7 and 3-methylguanine on day 28. On day 34 of age, the FUT1^AA pigs had higher levels of S-2-hydroxyglutarate, L-phenylalanine, tauroursodeoxycholic acid and an undetermined PC/LysoPC, while Ile Glu Phe Gly peptide and genistein 5-O-glucuronide, and PC (18:0/0:0) were at higher levels in the FUT1^AG piglets. FUT1 genotype did not affect the growth performance and expression of candidate genes. FUT1^AG piglets had a higher number of haemolytic bacteria in faeces and in digesta than that in FUT1^AA at 34 days of age. The colonic acetic acid concentration was highest in FUT1^AG piglets. FUT1 genotype may influence not only the expression of E. coli F18 receptors but could potentially impact the gut homeostasis and metabotype of piglets pre and post-weaning. Further investigations on the relation between FUT1 genotype and these aspects including the intestinal commensal microbiota will expand the knowledge on factors affecting the intestinal ecosystem.

Bilayer polymeric nanocapsules: A formulation approach for a thermostable and adjuvanted E. coli antigen vaccine

One of the strategies used to improve the immunogenicity of purified protein antigens has relied on their association with synthetic nanocarriers, which, in general, have functioned as simple antigen containers. Here, we present a more advanced strategy based on the design of an antigen nanocarrier at the molecular level. The nanocarrier is composed of a vitamin E oily core, surrounded by two layers: a first layer of chitosan and a second of dextran sulphate. The selected antigen, IutA protein from Escherichia coli, was harboured between the two polymeric layers. The final bilayer nanocapsules had a nanometric size (≈ 200 nm), a negative zeta potential (< -40 mV) and a good antigen association efficiency (≈ 70%). The bilayer architecture led to an improvement on the formulation stability and the controlled release of the associated antigen. Remarkably, after being administered to mice, bilayer nanocapsules elicited higher IgG levels than those obtained with antigen precipitated with Alum. Moreover, freeze-dried nanocapsules were stable at room temperature for, at least, 3 months. These promising data, in addition to their contribution to the development of an uropathogenic E. coli vaccine, has allowed us to validate these novel bilayer nanocapsules as adequate platforms for the delivery of protein antigens.

Clinical predictors of escalating care in hepatic and renal cyst infection in autosomal dominant polycystic kidney and liver disease

BACKGROUND

Cyst infection may occur in autosomal dominant polycystic kidney disease (ADPKD) and autosomal dominant polycystic liver disease (ADPLD). Antimicrobial agents often fail to control infection, leading to invasive action. We aimed to identify factors predicting escalation of care.

METHODS

ADPKD and ADPLD patients were identified from local/national databases (2001-2013). Records were screened for patients meeting criteria for cyst infection (positive cyst aspirate and/or clinical findings). Factors that predict escalated care were identified with multivariate modified Poisson regression.

RESULTS

We screened 1773 patients. A total of 77 patients with cyst infection (4.3%) were included for analysis (hepatic 36%; male 49%; age 54 ±; 13 years; ADPKD 95%; dialysis 9%, diabetes 18%, renal transplant 56%, eGFR [IQR 24-78] ml/min/1.73 m2 (excluding patients with a history of renal transplant or receiving dialysis)). A pathogen was identified in 71% of cases. Escherichia coli was the most common pathogen and accounted for 69% of cases. Initial treatment was limited to antibiotics in 87% of patients (n = 67), 40% included a fluoroquinolone. Ultimately, 48% of patients underwent some form of invasive action (escalation of care). Increasing white blood cell count (WBC) (RR 1.04 95%-CI 1.01-1.07, p = 0.008) was associated with escalating care, whereas an increase in time between transplant and infection (RR 0.92 95% CI 0.86-0.97, p = 0.005) and E. coli isolation (RR 0.55 95% CI 0.34-0.89, p = 0.02) were protective.

CONCLUSION

High serum WBC, isolation of atypical pathogens and early infection after transplantation are factors that increase the risk of escalation of care in hepatic and renal cyst infection patients.

Bacteria isolated from companion animals in Japan (2014-2016) by blood culture

We aimed to identify microorganisms isolated by blood culture (BC) from companion animals and to determine antimicrobial resistance of these isolates during 2014-2016 at veterinary laboratory, in comparison with those during 2010-2013, in Japan. Clinical data (animal species, visiting animals/hospitalized animals, and others except for disease type and clinical course including history of antimicrobial agent use) on ill animals at veterinary clinics or hospitals were obtained. We retrospectively analyzed animal-origin BC results extracted from the database in 2014-2016 and those obtained in 2010-2013. BC-positive samples were from most of dogs (n = 174 in 2014-2016 and n = 86 in 2010-2013). Escherichia coli (n = 50, 25.1%) and Staphylococcus intermedius group (SIG) bacteria (n = 23, 11.6%) were most prevalent in 2014-2016, while the percentages of E. coli (n = 22, 25.3%) and SIG (n = 9, 10.3%) in 2010-2013 were similar to those in 2014-2016. Percentages of extended-spectrum β-lactamase (ESBL)-producing E. coli and methicillin-resistant staphylococci (MRS) rate of SIG bacteria isolated in 2014-2016 were 28.0% and 69.6% (vs. 22.7% and 44.4% in 2010-2013), respectively. Fourteen ESBL-producing E. coli in 2014-2016 were isolated from 7 visiting animals and 7 hospitalized ones, whereas the sixteen MRS of SIG were from 7 visiting animals and 9 hospitalized ones. Our observations support the prevalent microorganisms isolated by BC and their antimicrobial resistance patterns for two study periods.

Gastroenteritis in an adult female revealing hemolytic uremic syndrome: Case report

Nowadays acute gastroenteritis infection caused by Escherichia coli (E. coli) O157:H7 is frequently associated with hemolytic uremic syndrome (HUS), which usually developed after prodromal diarrhea that is often bloody. The abdominal pain accompanied by failure kidney is a suspicious symptom to develop this disorder. Their pathological characteristic is vascular damage which manifested as arteriolar and capillary thrombosis with abnormalities in the endothelium and vessel walls. The major etiological agent of HUS is enterohemorragic (E coli) strain belonging to serotype O157:H7. The lack of papers about HUS associated to gastroenteritis lead us to report this case for explain the symptoms that are uncommon. Furthermore, this report provides some strategies to suspect and make an early diagnosis, besides treatment approach to improving outcomes and prognosis for patients with this disorder.

Combined Enteral and Parenteral Glutamine Supplementation in Endotoxemic Swine: Effects on Portal and Systemic Circulation Levels

OBJECTIVE

To measure plasma glutamine (GLN) levels in systemic and portal circulation after combined enteral and parenteral administration in early endotoxemic swine. We hypothesized that this combination will be more efficient than intravenous administration alone in restoring plasma levels during the course of endotoxemia.

MATERIALS AND METHODS

Endotoxemia was induced with Escherichia coli O111:B4 lipopolysaccharide (LPS) (250 μg/kg body weight) in 16 anes-thetized, fasted swine and maintained by constant infusion (2 μg/kg/h) over 180 min. Another 16 swine served as controls. After infusion with LPS or placebo, GLN was administered intravenously, enterally or in combination (0.5 g/kg i.v. plus 0.5 g/kg enterally) over 30 min. At 0, 15, 30, 45, 60, 120 and 180 min, blood was drawn from the systemic and portal circulation for colorimetric assessment of GLN.

RESULTS

In healthy, placebo-alone swine, GLN levels remained stable throughout the study. Intravenous and combined infusion increased systemic levels (p = 0.001), but after enteral administration alone, a smaller effect was observed (p = 0.026). Portal levels were increased after combined, enteral and intravenous administration (p = 0.001). In endotoxemia, systemic and portal levels decreased significantly. Intravenous and, to a greater extent, combined administration increased systemic levels (p = 0.001), while enteral administration only had a small effect (p = 0.001). In the portal vein, intravenous and combined treatment increased plasma levels (p = 0.001), whereas enteral supplementation alone had again a small, yet significant effect (p = 0.001).

CONCLUSIONS

The findings indicate that combined GLN supplementation is superior to intravenous treatment alone, in terms of enhanced availability in systemic and portal circulations. Thus, combined treatment at the onset of endotoxemia is a beneficial practice, ensuring adequate GLN to compensate for the resulting intracellular shortage.

[Antibiotic Resistance and Risk Factors for Mortality of Blood Stream Infections (BSIs) with Escherichia coli in Patients with Hematological Malignancies]

OBJECTIVE

To analyze the risk factors for mortality of blood stream infections (BSIs) caused by Escherichia coli in the patients with hematological malignancies.

METHODS

There were 110 Escherichia coli BSIs patients with hematological malignancies included in recent five years. Among them,77 cases had BSIs caused by extended-spectrum-beta-lactamase (ESBL)-producing Escherichia coli (ESBL-EC group),while 33 cases had BSIs with non-ESBL-producing Escherichia coli (non-ESBL-EC group). The antibiotic resistance and clinical features were compared between the two groups,and the risk factors for death within 30 d were analyzed.

RESULTS

Less than 10% of the isolates were resistant to carbapenems and amikacin. Between ESBL-EC group and non-ESBL-EC group,the clinical symptoms,prior use of antibiotics or antifungal agents,risk factors for infection,30 d mortality rates were not significantly different (P>0.05). A logistic regression analysis confirmed that non remission of hematologic malignancies (odds ratio=9.575,95% confidence interval 1.546-59.312,P=0.015) and inappropriate initial antibiotic therapy (odds ratio=8.806,95% confidence interval 1.527-50.772, P=0.015) were independent risk factors for 30 d mortality.

CONCLUSION

The use of effective antimicrobial treatment as early as possible could reduce the risk of death for hematological malignancies patients suffering Escherichia coli BSIs.

Binge alcohol consumption 18 h after induction of sepsis in a mouse model causes rapid overgrowth of bacteria, a cytokine storm, and decreased survival

Alcohol abuse increases vulnerability to infections and infection-related mortality. In previous studies, we found that acute alcohol abuse in a binge-drinking model in mice decreased resistance to bacterial sepsis when alcohol was administered near the time of bacterial challenge. In the present study, we investigated the effects of alcohol administered later in the course of sepsis (18 h after injection of Escherichia coli). Our working hypothesis was that decreased production of cytokines caused by alcohol at this time would actually improve survival, because overproduction of pro-inflammatory mediators is thought to be the proximate cause of mortality in sepsis. Unexpectedly, administration of alcohol late in the course of sepsis led to a rapid increase in the number of viable bacteria in the peritoneal cavity. Significant increases in the concentrations of several cytokines and chemokines coincided with the increased number of bacteria in alcohol-treated mice and decreased survival time. These results demonstrated our working hypothesis to be incorrect, and reiterated the complexity of sepsis. Hypothermia is a consistent feature in this model of sepsis. In control mice (E. coli only), body temperature was near normal by 18 h or 21 h after administration of E. coli, but in mice treated with alcohol 18 h after E. coli, hypothermia was significant 3 h later and ultimately mortality was significantly increased. However, counteracting the hypothermic effect of alcohol by external warming of mice led to earlier mortality, demonstrating that hypothermia was not the major cause of mortality. These results, along with previous results from studies in which alcohol was given before initiation of sepsis, suggest that decreased cytokine and chemokine production may not be the key effect of alcohol that decreases resistance to sepsis. It seems more likely that suppression of mechanisms by which macrophages and neutrophils kill bacteria is critical, and this can occur even in the presence of high levels of cytokines and chemokines.

Effects of low-dose irradiation on mice with Escherichia coli-induced sepsis

Although favorable immune responses to low-dose irradiation (LDI) have been observed in normal mice, i.e., a hormesis effect, little is known about the effects of LDI in infectious diseases. In this study, we examined the effects of LDI on mice with sepsis, a severe and often lethal hyperinflammatory response to bacteria. Female C57BL/6 mice were whole-body irradiated with 10cGy 48h before Escherichia coli infection, and survival, bacterial clearance, cytokines, and antioxidants were quantified. LDI pretreatment significantly increased survival from 46.7% in control mice to 75% in mice with sepsis. The bacterial burden was significantly lower in the blood, spleen, and kidney of LDI-treated mice than in those of control septic mice. The levels of pro-inflammatory cytokines, e.g., IL-1β and IL-6, as well as anti-inflammatory IL-10 were markedly reduced in pre-LDI septic mice. Nitric oxide production by peritoneal macrophages was also reduced in pre-LDI septic mice. Immune cells in the spleen increased and Nrf2 and HO-1 were induced in pre-LDI septic mice. LDI stimulates the immune response and minimizes lethality in septic mice via enhanced bacterial clearance and reduced initial proinflammatory responses.

Novel mcr-3 variant, encoding mobile colistin resistance, in an ST131 Escherichia coli isolate from bloodstream infection, Denmark, 2014

A novel variant of the plasmid-borne colistin resistance gene mcr-3 was detected on an IncHI2 plasmid in an ST131 CTX-M-55-producing Escherichia coli isolate from a Danish patient with bloodstream infection in 2014. The discovery of novel plasmid-borne genes conferring resistance to colistin is of special interest since colistin has reemerged as an important drug in the treatment of infections with multidrug-resistant Gram-negative bacteria.

Will co-trimoxazole resistance rates ever go down? Resistance rates remain high despite decades of reduced co-trimoxazole consumption

OBJECTIVE

Several studies showed that a substantial decline in the use of co-trimoxazole did not result in a decline in resistance rates among Escherichia coli isolates. Since mathematical models have shown that it may take decades before resistance rates start to decline to relevant levels, we performed a new analysis using more recently collected data.

METHODS

Data were extracted from Guy's and St Thomas' Hospitals Transmission and Antimicrobial Record database which contains microbiological test results from all specimens tested between 2002 and 2014. We selected all blood samples positive for E. coli which were tested for resistance against co-trimoxazole. Prevalence of co-trimoxazole resistance among the tested samples by year was modelled by a Poisson model.

RESULTS

Almost all (96%) of E. coli blood isolates were tested for co-trimoxazole resistance. In total, 2070 E. coli isolates were available for analyses. Resistance to co-trimoxazole fluctuated over the years, but there was no clear increasing or decreasing trend; the annual percentage change in the prevalence of co-trimoxazole resistance was 0.52 (95% confidence interval -0.75% to 1.81%). Including co-trimoxazole or trimethoprim use in the year before the sample was taken did not improve the model.

CONCLUSION

The prevalence of co-trimoxazole resistance among E. coli blood isolates remained high, almost three decades after a substantial decline in co-trimoxazole use. Our results further emphasize the importance of prudent antibiotics use, as antibiotic resistance may not always be easily reversible.

Endothelial dysfunction during long-term follow-up in children with STEC hemolytic-uremic syndrome

BACKGROUND

Shiga-toxin-producing Escherichia coli (STEC)-associated hemolytic-uremic syndrome (HUS) is a major cause of acute kidney injury (AKI), especially in children. Its long-term outcome with respect to endothelial damage remains largely elusive.

METHODS

This was a cross-sectional study in 26 children who had suffered from STEC-HUS in the past and achieved a complete recovery of renal function (eGFR >90 ml/min/1.73 m²). Skin microcirculation after local heating was assessed by laser Doppler fluximetry, carotid-femoral pulse wave velocity (PWV), carotid intima media thickness (cIMT), 24-h ambulatory blood pressure, and angiopoietin (Ang) 1 and 2 serum levels after a median follow-up period of 6.1 years. The results were compared to those of healthy controls.

RESULTS

All patients were normotensive, mean eGFR was 102 (range 91-154) ml/min/1.73 m², and 13 of the 26 patients showed albuminuria. Endothelial dysfunction was present in 13 patients, and the mean serum Ang2/Ang1 ratio was increased compared to healthy children (each p < 0.05). In contrast, mean values for PWV and cIMT in the patients did not differ from those of the controls. Endothelial dysfunction was significantly associated with younger age at STEC-HUS manifestation, time after HUS, and presence of albuminuria.

CONCLUSION

The results of this study highlight the need for long-term follow-up of STEC-HUS patients even after complete recovery of eGFR and lack of hypertension with respect to microvascular damage.

Unusual severe case of hemolytic uremic syndrome due to Shiga toxin 2d-producing E. coli O80:H2

BACKGROUND

Hemolytic uremic syndrome (HUS) is one of the most common causes of acute renal failure in children, with the majority of cases caused by an infection with Shiga toxin-producing Escherichia coli (STEC). Whereas O157 is still the predominant STEC serotype, non-O157 serotypes are increasingly associated with STEC-HUS. However, little is known about this emerging and highly diverse group of non-O157 serotypes. With supportive therapy, STEC-HUS is often self-limiting, with occurrence of chronic sequelae in just a small proportion of patients.

CASE DIAGNOSIS/TREATMENT

In this case report, we describe a 16-month-old boy with a highly severe and atypical presentation of STEC-HUS. Despite the presentation with multi-organ failure and extensive involvement of central nervous system due to extensive thrombotic microangiopathy (suggestive of atypical HUS), fecal diagnostics revealed an infection with the rare serotype: shiga toxin 2d-producing STEC O80:H2.

CONCLUSIONS

This report underlines the importance of STEC diagnostic tests in all children with HUS, including those with an atypical presentation, and emphasizes the importance of molecular and serotyping assays to estimate the virulence of an STEC strain.

Platelet-borne complement proteins and their role in platelet-bacteria interactions

Essentials Platelets play an important role in pathogen recognition. Platelets contain several complement factors and can interact with E. coli. Platelet's complement protein C3 differs from plasmatic C3 in its electrophoretic mobility. Upon contact with bacteria, platelets are activated and can enhance complement activation.

SUMMARY

Background The role of platelets in immune defense is increasingly being recognized. Platelets bind complement proteins from plasma, initiate complement activation, and interact with bacteria. However, the contribution of platelets to complement-mediated defense against bacterial infections is not known in detail. Objectives To assess platelet interactions with Escherichia coli strains, and evaluate the contributions of platelet complement proteins to host defense. Methods We studied the cell-cell interactions of a pathogenic and a non-pathogenic E. coli strain with platelet concentrates, washed platelets and manually isolated platelets by flow cytometry and ELISA. The presence of complement proteins and complement RNA in megakaryocytes and platelets was analyzed by PCR, RT-PCR, confocal microscopy, and western blotting. Results Incubation with E. coli leads to platelet activation, as indicated by the expression of CD62P and CD63 on the platelet surface. RNA and protein analyses show that megakaryocytes and platelets contain complement C3, and that platelet C3 migrates differently on polyacrylamide gels than plasmatic C3. Activation of platelets by bacteria leads to translocation of C3 to the cell surface. This translocation is not induced by thrombin receptor activating peptide or lipopolysaccharide. Interaction of platelets with E. coli occurs even in the absence of plasma proteins, and is independent of platelet toll-like receptor 4 and α2b β3 (glycoprotein IIbIIIa). Conclusion Platelets contain a specific form of C3. Importantly, they can modulate immune defense against bacteria by enhancing plasmatic complement activation.

Descriptive epidemiology of Escherichia coli bacteraemia in England, April 2012 to March 2014

We determined the incidence, risk factors and antimicrobial susceptibility associated with Escherichia coli bacteraemia in England over a 24 month period. Case data were obtained from the national mandatory surveillance database, with susceptibility data linked from LabBase2, a voluntary national microbiology database. Between April 2012 and March 2014, 66,512 E. coli bacteraemia cases were reported. Disease incidence increased by 6% from 60.4 per 100,000 population in 2012-13 to 63.5 per 100,000 population in 2013-14 (p < 0.0001). Rates of E. coli bacteraemia varied with patient age and sex, with 70.5% (46,883/66,512) of cases seen in patients aged ≥ 65 years and 52.4% (33,969/64,846) of cases in females. The most common underlying cause of bacteraemia was infection of the genital/urinary tract (41.1%; 27,328/66,512), of which 98.4% (26,891/27,328) were urinary tract infections (UTIs). The majority of cases (76.1%; 50,617/66,512) had positive blood cultures before or within two days of admission and were classified as community onset cases, however 15.7% (10,468/66,512) occurred in patients who had been hospitalised for over a week. Non-susceptibility to ciprofloxacin, third-generation cephalosporins, piperacillin-tazobactam, gentamicin and carbapenems were 18.4% (8,439/45,829), 10.4% (4,256/40,734), 10.2% (4,694/46,186), 9.7% (4,770/49,114) and 0.2% (91/42,986), respectively. Antibiotic non-susceptibility was higher in hospital-onset cases than for those presenting from the community (e.g. ciprofloxacin non-susceptibility was 22.1% (2,234/10,105) for hospital-onset vs 17.4% (5,920/34,069) for community-onset cases). Interventions to reduce the incidence of E. coli bacteraemia will have to target the community setting and UTIs if substantial reductions are to be realised.

Urinary Tract Infection in Childhood and Inflammatory Markers>

Acute urinary tract infections are common in children. Our aim was to establish whether peripheral blood tests correlate with urinary culture. We also examined the relationship between peripheral blood results and the length of stay (LOS) in children and adolescents with UTI. We studied 135 patients admitted with UTI, mean (SD) age 3.0 (4.1) years. Of these 135 patients, 16 (11.9%) had combined normal serum WCC, normal neutrophil count and CRP < 5 mg/L. In this group of patients, there was no significant association between LOS and serum WCC, serum neutrophil values, E. coli infection or CRP values (p value 0.51, 0.98, 0.87, 0.82, respectively).

Usefulness of analytical parameters in the management of paediatric patients with suspicion of acute pyelonephritis. Is procalcitonin reliable?

OBJECTIVE

To investigate the usefulness of procalcitonin (PCT) and other analytical parameters (white blood cell count [WBC], C-reactive protein [CRP]) as markers of acute renal damage in children after a first febrile or afebrile urinary tract infection (UTI).

METHODS

A retrospective study was conducted on children with a first episode of UTI admitted between January 2009 to December 2011, and in whom serum PCT, CRP and white blood cell count were measured, as well as assessing the acute renal damage with renal scintigraphy with ^99mTc-DMSA (DMSA) within the first 72h after referral. A descriptive study was performed and ROC curves were plotted, with optimal cut-off points calculated for each parameter.

RESULTS

The 101 enrolled patients were divided into two groups according to DMSA scintigraphy results, with 64 patients being classified with acute pyelonephritis (APN), and 37 with UTI. The mean WBC, CRP and PCT values were significantly higher in patients with APN with respect to normal acute DMSA. The area under the ROC curve was 0.862 for PCR, 0.774 for WBC, and 0.731 for PCT. The optimum statistical cut-off value for PCT was 0.285ng/ml (sensitivity 71.4% and specificity 75%).

CONCLUSION

Although the mean levels of fever, WBC, CRP, and PCT were significantly increased in patients with APN than in those who had UTI, the sensitivity and specificity of these analytical parameters are unable to predict the existence of acute renal damage, making the contribution by renal DMSA scintigraphy essential.

Escherichia coli induces platelet aggregation in an FcγRIIa-dependent manner

BACKGROUND

The discovery of pathogen-recognition receptors such as Toll-like receptors on platelets has led to the emergence of the concept of platelets as important components of the host response to infection. Escherichia coli (E. coli)-mediated sepsis is a serious illness characterized by the occurrence of thrombocytopenia. Whereas there has been a wealth of research on platelet activation by Gram-positive bacteria, little is known about the mechanisms associated with Gram-negative bacteria-induced platelet activation with Gram-negative bacteria.

OBJECTIVES

To determine the mechanisms by which Gram-negative E. coli induces platelet aggregation.

METHODS

Induction of platelet aggregation with E. coli strain O157:H7 was tested in platelet-rich plasma (PRP), washed platelets, and serum depleted of complement factors. Platelet inhibitors (against αII b β3 , glycoprotein Ibα and FcγRIIa) were used. Platelet thromboxane synthesis was analyzed after E. coli stimulation. Cell binding assays were used to assess the ability of E. coli to support platelet adhesion. Trypsinization was used to determine the role of E. coli surface proteins.

RESULTS AND CONCLUSION

E. coli-induced aggregation in PRP was donor-dependent. E. coli O157:H7 induced aggregation with a lag time of 6.9 ± 1.3 min in an αII b β3 -dependent and FcγRIIa-dependent manner. Furthermore, this interaction was enhanced by the presence of complement, and was dependent on thromboxane synthesis. These results show E. coli to be a potent inducer of platelet aggregation.

Fecal diagnostics in combination with serology: best test to establish STEC-HUS

BACKGROUND

In the majority of pediatric patients, the hemolytic-uremic syndrome (HUS) is caused by an infection with Shiga toxin-producing Escherichia coli (STEC), mostly serotype O157. It is important to discriminate between HUS caused by STEC and complement-mediated HUS (atypical HUS) due to differences in treatment and outcome. As STEC and its toxins can only be detected in the patient's stool for a short period of time after disease onset, the infectious agent may go undetected using only fecal diagnostic tests. Serum antibodies to lipopolysaccharide (LPS) of STEC persist for several weeks and may therefore be of added value in the diagnosis of STEC.

METHODS

All patients with clinical STEC-HUS who were treated at Radboud University Medical Center between 1990 and 2014 were included in this retrospective single-center study. Clinical and diagnostic microbiological data were collected. Immunoglobulin M (IgM) antibodies against LPS of STEC serotype O157 were detected by a serological assay (ELISA).

RESULTS

Data from 65 patients weres available for analysis. Fecal diagnostic testing found evidence of an STEC infection in 34/63 patients (54 %). Serological evidence of STEC O157 was obtained in an additional 16 patients. This is an added value of 23 % (p < 0.0001) when the serological antibody assay is used in addition to standard fecal diagnostic tests to confirm the diagnosis STEC-HUS. This added value becomes especially apparent when the tests are performed more than 7 days after the initial manifestation of the gastrointestinal symptoms.

CONCLUSIONS

The serological anti-O157 LPS assay clearly makes a positive contribution when used in combination with standard fecal diagnostic tests to diagnose STEC-HUS and should be incorporated in clinical practice.

Depletion of polymorphonuclear leukocytes has no effect on preterm delivery in a mouse model of Escherichia coli-induced labor

OBJECTIVE

The objective of the study was to investigate the role of polymorphonuclear leukocytes (PMNs) in a mouse model of Escherichia coli-induced labor.

STUDY DESIGN

Intraperitoneal injection of rabbit antimouse PMN antiserum or control was performed in CD-1 mice 29 hours and 5 hours prior to laparotomy and intrauterine injection of either killed E coli or phosphate-buffered saline on day 14.5 of pregnancy. Preterm delivery was defined as delivery of at least 1 pup within 48 hours. Circulating leukocyte counts were determined manually or by flow cytometry at the time of surgery and 8, 24, and 48 hours afterward. Maternal and fetal tissues were analyzed in a separate group of animals 8 hours after surgery.

RESULTS

Pretreatment with anti-PMN antiserum significantly decreased the numbers of circulating leukocytes and the proportion of neutrophils among all leukocytes by 70-80% at surgery and at least 8 hours thereafter. Neutrophil depletion significantly reduced 2 markers of neutrophil activation in the uterus and placenta (neutrophil elastase and myeloperoxidase activity) and neutrophil infiltration into gestational tissues in bacterially treated animals to baseline (control) levels but did not affect preterm birth rates. The large E coli-induced increases in uterine inflammatory markers (interleukin-1β, tumor necrosis factor, chemokine ligand-5, cyclooxygenase-2) were not affected or were only minimally affected by neutrophil depletion.

CONCLUSION

Although PMN antiserum reduces both neutrophil number and activity, it does not diminish sensitivity to bacterially induced delivery or meaningfully alter the expression of inflammatory markers in the mouse model. Preterm birth and inflammation in this model are not likely to depend on neutrophil function.

Effects of Fuzhuan Brick-Tea Water Extract on Mice Infected with E. coli O157:H7

Fuzhuan brick-tea extract (FBTE) affects the physiology of mice infected with Escherichia coli O157:H7. For 10 consecutive days, 0.05, 0.5, and 1.0 g/mL FBTE was administered intragastrically to three groups of infected Kunming mice, and changes in immunological function, hematology, and histopathology were examined. The results revealed upregulation of platelets, total protein, and albumin along with downregulation of serum triglycerides, aspartate aminotransferase, creatinine, and urea nitrogen in FBTE-treated mice. Histological sections of stomach, kidney, duodenum, ileum, and colon suggested that infected mucous membranes could be rehabilitated by low- and high-dose FBTE and that inflammation was alleviated. Similarly, increased thymic function in mice treated with middle- and high-dose FBTE led to elevated serum hemolysin antibody titer and increased CD4⁺ and CD8⁺ T cells, as indicated by CD4⁺ and CD8⁺ expression on intestinal mucosa. Monocyte and macrophage function was improved by three FBTE dosages tested. Colonic microbiota analysis by denaturing gradient gel electrophoresis (DGGE) revealed characteristic bands in infected mice treated with middle- and high-dose FBTE and increased species diversity in Lactobacillus, Bacteroides, and Clostridium cluster IV. These results suggest that FBTE may protect kidney and liver of mice infected with E. coli O157:H7, improve immune function, and regulate the colonic microbiota.

Survival advantage of heterozygous factor V Leiden carriers in murine sepsis

BACKGROUND

The high allelic frequency of the prothrombotic Leiden polymorphism in human blood coagulation factor V (FV) has been speculated to reflect positive selection during evolution. Heterozygous Leiden carriers enrolled in the placebo arm of the PROWESS sepsis trial and heterozygous Leiden mice challenged with endotoxin both showed reduced mortality, whereas homozygous Leiden mice were not protected from lethal endotoxemia. Follow-up analyses of clinical outcomes and of mouse models of infection with various pathogens remained inconclusive.

OBJECTIVE

To establish whether activated protein C resistance of FV Leiden modifies the outcome of bacterial infection in murine sepsis models.

METHODS

Homozygous and heterozygous FV Leiden mice were subjected to gram-positive (S. aureus) or gram-negative (Y. pestis; E. coli) septic peritonitis or polymicrobial, focal septic peritonitis induced by cecal ligation and puncture. The effect of FV Leiden on 7-day survival and bacterial dissemination was assessed. Outcomes were compared with the sepsis survival of mice with genetically impaired hemostasis (hemophilia A, thrombocytopenia, thrombin receptor PAR4 [protease activated receptor 4] deficiency, endothelial protein C receptor [ProcR/EPCR] deficiency).

RESULTS

Heterozygous, but not homozygous, Leiden mice were protected from lethal infection with highly virulent S. aureus and Y. pestis strains. FV Leiden did not affect the outcome of sepsis induced by cecal ligation and puncture, staphylokinase-deficient S. aureus, Pla-deficient Y. pestis, or E. coli. Thrombocytopenia, deficiency of PAR1 or PAR4 did not affect S. aureus sepsis survival, whereas hemophilia A increased mortality. ProcR deficiency selectively abolished the survival advantage of heterozygous Leiden mice.

CONCLUSIONS

In mice, heterozygous FV Leiden carriers are protected from sepsis mortality after infection with clinically relevant human bacterial pathogens.

Soluble plasma VE-cadherin concentrations are elevated in patients with STEC infection and haemolytic uraemic syndrome: a case-control study

OBJECTIVES

To investigate whether the adherens junction protein vascular endothelial cadherin (VE-cadherin) is released during Shiga toxin 2 producing Escherichia coli (STEC) infection with haemolytic uraemic syndrome (HUS) and thus could be used to assist diagnosis.

DESIGN

Using data from the large 2011 STEC outbreak in northern Europe, we determined VE-cadherin plasma concentrations in 356 patients distributed over three patient cohorts: patients with STEC infection accompanied by HUS (STEC-HUS), STEC patients without HUS (STEC) and control patients with diarrhoea but without STEC infection. We then looked for associations between VE-cadherin concentrations and disease severity defined by changes in lactate dehydrogenase, haemoglobin, creatinine, platelet count, haptoglobin and neurological symptoms.

SETTING

This study was conducted at the University Medical Center Hamburg-Eppendorf, Germany.

PARTICIPANTS

79 STEC-HUS patients, 77 STEC patients and 200 control patients were enrolled in the study.

RESULTS

We analysed 864 specimens (207 STEC, 449 STEC-HUS and 208 controls) in total. At admission, VE-cadherin concentration tended to be lower in STEC-HUS patients compared to other patients. However, HUS patients later showed an increase in VE-cadherin concentrations with prolonged elevation beyond remission. This pattern clearly differs from that observed in non-HUS patients.

CONCLUSIONS

VE-cadherin concentrations are elevated in STEC-HUS patients and might be a biomarker reflecting endothelial damage in patients with HUS.

ESBL-producing Escherichia coli isolated from bloodstream infections--antimicrobial susceptibility, conjugative transfer of resistance genes and phylogenetic origin

BACKGROUND

The prevalence of bloodstream infections (BSIs) due to ESBL-producing Escherichia coli (ESBL-EC) strains has increased dramatically over the past years.

OBJECTIVES

Characterization of ESBL-EC isolates collected from BSIs with regard to their antimicrobial susceptibility and phylogenetic background. The conjugative transfer of resistance determinants to the E. coli reference strain K12 C600 was also investigated.

MATERIAL AND METHODS

A collection of forty-eight ESBL-EC strains recovered from BSIs was subjected to the study. These strains were obtained from the ICU (intensive care unit) of the Medical University Hospital, Wrocław, Poland, during a four-year period (2009-2012). All the isolates were screened for ESBL production by the double disk synergy test (DDST). Transferability of plasmid-mediated resistance genes was performed by the conjugational broth method. Susceptibility to antibiotics and chemotherapeutics of clinical isolates and transconjugants was determined by the agar dilution method. PCR assay was used to detect the blaCTX-M gene in ESBL-EC tested and transconjugants. Affiliation to phylogenetic groups was done by the triplex PCR method.

RESULTS

Conjugational transfer of plasmids responsible for ESBL to a recipient strain was successful for all the ESBL-EC analyzed (donors). The conjugation frequencies ranging from 2.3×10(-7) to 5.2×10(-1) per donor. In vitro susceptibility testing revealed that all the ESBL-EC isolates and their transconjugants were resistant to most of the antimicrobial agents tested with the exception of carbapenems, tigecycline, and β-lactam-clavulanate combinations. Moreover, all the donor strains and their transconjugants were found to contain the blaCTX-M gene. The majority of the isolates analyzed belonged to phylogroups B2 (62.5%) and D (25%), whereas groups B1 and A were less frequently represented (8.3% and 4.2%, respectively).

CONCLUSIONS

The results of the study confirm the need of antibiotic policies and effective infection control measures in hospital settings to minimize BSIs caused by multi-resistant ESBL-producing pathogens.

Prolonged clonal spreading and dynamic changes in antimicrobial resistance of Escherichia coli ST68 among patients who stayed in a respiratory care ward

From 2007 to 2009, we collected a total of 83 bacteraemic isolates of Escherichia coli with reduced susceptibility or resistance to third-generation cephalosporins (TGCs). Isolates were genotyped by PFGE and multilocus sequence typing (MLST). The PFGE patterns revealed two highly correlated clusters (cluster E: nine isolates; cluster G: 22 isolates) associated with this prolonged clonal spreading. Compared with cluster E isolates, cluster G isolates were significantly more likely to harbour aac(6')-Ib-cr (P<0.05), and most of these isolates were isolated during a later year than cluster E isolates (P<0.05). By MLST analysis, 94% of cluster E and G isolates (29/31) were ST68. Although no time or space clustering could be identified by the conventional hospital-acquired infection monitoring system, E. coli cases caused by cluster E and G isolates were significantly associated with having stayed in our hospital's respiratory care ward (P<0.05). Isolates obtained from patients who had stayed in the respiratory care ward had a significantly higher rate of aac(6')-Ib-cr and blaCTX-M-14 positivity, and were more likely to belong to ST68/S68-like (all P<0.05). To our knowledge, this is the first report of prolonged clonal spreading caused by E. coli ST68 associated with a stay in a long-term care facility. Using epidemiological investigations and PFGE and MLST analyses, we have identified long-term clonal spreading caused by E. coli ST68, with extra antimicrobial-resistance genes possibly acquired during the prolonged spreading period.

Nuclease-assisted suppression of human DNA background in sepsis

Sepsis is a severe medical condition characterized by a systemic inflammatory response of the body caused by pathogenic microorganisms in the bloodstream. Blood or plasma is typically used for diagnosis, both containing large amount of human DNA, greatly exceeding the DNA of microbial origin. In order to enrich bacterial DNA, we applied the C₀t effect to reduce human DNA background: a model system was set up with human and Escherichia coli (E. coli) DNA to mimic the conditions of bloodstream infections; and this system was adapted to plasma and blood samples from septic patients. As a consequence of the C₀t effect, abundant DNA hybridizes faster than rare DNA. Following denaturation and re-hybridization, the amount of abundant DNA can be decreased with the application of double strand specific nucleases, leaving the non-hybridized rare DNA intact. Our experiments show that human DNA concentration can be reduced approximately 100,000-fold without affecting the E. coli DNA concentration in a model system with similarly sized amplicons. With clinical samples, the human DNA background was decreased 100-fold, as bacterial genomes are approximately 1,000-fold smaller compared to the human genome. According to our results, background suppression can be a valuable tool to enrich rare DNA in clinical samples where a high amount of background DNA can be found.

The bacterial amyloid curli is associated with urinary source bloodstream infection

Urinary tract infections are the most common cause of E. coli bloodstream infections (BSI) but the mechanism of bloodstream invasion is poorly understood. Some clinical isolates have been observed to shield themselves with extracellular amyloid fibers called curli at physiologic temperature. We hypothesize that curli fiber assembly at 37°C promotes bacteremic progression by urinary E. coli strains. Curli expression by cultured E. coli isolates from bacteriuric patients in the presence and absence of bacteremia were compared using Western blotting following amyloid fiber disruption with hexafluoroisopropanol. At 37°C, urinary isolates from bacteremic patients were more likely to express curli than those from non-bacteremic patients [16/22 (73%) vs. 7/21 (33%); p = 0.01]. No significant difference in curli expression was observed at 30°C [86% (19/22) vs. 76% (16/21); p = 0.5]. Isolates were clonally diverse between patients, indicating that this phenotype is distributed across multiple lineages. Most same-patient urine and blood isolates were highly related, consistent with direct invasion of urinary bacteria into the bloodstream. 37°C curli expression was associated with bacteremic progression of urinary E. coli isolates in this population. These findings suggest new future diagnostic and virulence-targeting therapeutic approaches.

[Evaluation of usefulness of the enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to lipopolysaccharides of Enterohemorrhagic Escherichia coli (EHEC) strains in patients with gastrointestinal disorders and patients with hemolytic uremic syndrome]

INTRODUCTION

Enterohemorrhagic Escherichia coli (EHEC) strains are an important zoonotic food-borne and waterborne pathogens causing diarrhea and the severe hemolytic uremic syndrome (HUS) in humans. The aim of the study was to evaluate the usefulness of enzyme immunoassay ELISA for detection of antibodies to the lipopolysaccharides (LPS) of EHEC in patients with gastrointestinal disorders and patients with hemolytic-uremic syndrome.

MATERIAL AND METHODS

Sera obtained from 526 patients with gastrointestinal disorders, 26 patients with HUS and 74 patients with different bacterial gastroenteritis infections were screened by an LPS-based ELISA. The LPS antigens of EHEC belonging to serogroups O26, O103, O104, O111, O121, O145, and O157 were obtained by modified Boivin's method. Additionally, to determine the cut-off level, the 122 sera from healthy people were tested. Cellular extract from E. coli O14 were used to remove by absorption antibodies to the Enterobacteriaceae Common Antigen (ECA).

RESULTS

Generally, seroprevalence of antibodies to the LPS of different EHEC serogroups in patients with gastrointestinal disorders was low. Additionally, interpretation of the some positive results was difficult to the fact of many serological mutual interactions. Particularly a lot of cross-reactions were seen in the group of sera obtained from patients with different bacterial gastroenteritis infections. The study showed also that in most cases the absorption of antibodies to the ECA had no significant effect on the cross-reactions observed in ELISA. On the other hand, the very high level of antibodies to the LPS antigen of E. coli O26 was found in 5 patients, to E. coli O157 in 4 patients, to E. coli O104 and O145 in 3 patients and E. coli O111 in 2 patients with HUS. Analysis of antibody levels in paired sera taken 2-3 weeks apart obtained from six HUS patients showed a rapid decline of antibody levels to the LPS antigens.

CONCLUSIONS

The results showed the usefulness of the ELISA with lipopolysaccharides antigens to serodiagnosis of infection caused by EHEC. Due to the possibility of cross- -reaction there is a need to develop more specific antigens, based on the recombinant proteins of verotoxin-producing Escherichia coli.

Label-free in vivo imaging of human leukocytes using two-photon excited endogenous fluorescence

We demonstrate that two-photon excited endogenous fluorescence enables label-free morphological and functional imaging of various human blood cells. Specifically, we achieved distinctive morphological contrast to visualize morphology of important leukocytes, such as polymorphonuclear structure of granulocyte and mononuclear feature of agranulocyte, through the employment of the reduced nicotinamide adenine dinucleotide (NADH) fluorescence signals. In addition, NADH fluorescence images clearly reveal the morphological transformation process of neutrophils during disease-causing bacterial infection. Our findings also show that time-resolved NADH fluorescence can be potentially used for functional imaging of the phagocytosis of pathogens by leukocytes (neutrophils) in vivo. In particular, we found that free-to-bound NADH ratios measured in infected neutrophils increased significantly, which is consistent with a previous study that the energy consumed in the phagocytosis of neutrophils is mainly generated through the glycolysis pathway that leads to the accumulation of free NADH. Future work will focus on further developing and applying label-free imaging technology to investigate leukocyte-related diseases and disorders.

Changing epidemiology of bloodstream infection pathogens over time in adult non-specialty patients at an Australian tertiary hospital

The epidemiology of bloodstream infections (BSI) has been changing over time in developed countries. However, overview reports of BSI trends are limited in Australia. This descriptive epidemiological study analysed general and age-group specific trends, and antimicrobial susceptibility patterns of blood culture isolates between 2001 and 2009 in non-specialty adult patients at an Australian tertiary referral centre. A total of 3,051 isolates from 2,172 patients (60% males) were analysed. Both community onset (1,790 isolates, 59%) and hospital onset (1,261 isolates, 41%) BSIs were included. The mean age of patients was 59 ± 20 years; 930 patients (43%) were 70 years of age or over. Overall, 1,493 (49%) gram positive bacteria, 1,389 (46%) gram negative bacteria and 169 (5.5%) fungi were isolated. The proportion of gram negative isolates increased over the 9 years, (44% to 53%, P = 0.006) whilst gram positives decreased (49% to 45%, P = 0.045). These trends were significant in community onset infections but not hospital onset infections, and also in adult patients aged 20 years to less than 70 years but not in the elderly (≥70 years). Gram negative pathogens were most prevalent amongst the elderly (53% in the ≥70 years age group, P<0.0001 vs. 41% in the ≥20 to <70 years age group), attributable to an age-dependent increase in Escherichia coli infections and a decrease in Staphylococcus aureus infections (P<0.0001 for both). Most gram negative isolates remained susceptible to commonly prescribed antibiotics. By contrast, methicillin-resistant S. aureus rates decreased from 54% in 2001 to 28% in 2009 (P=0.007). This study found that gram negative BSIs appeared to be re-emerging, particularly in community onset infections and also amongst the younger patients at the study institution. Such epidemiological trends have important implications for antimicrobial choices for the treatment of undifferentiated sepsis.

Validation of treatment strategies for enterohaemorrhagic Escherichia coli O104:H4 induced haemolytic uraemic syndrome: case-control study

OBJECTIVE

To evaluate the effect of different treatment strategies on enterohaemorrhagic Escherichia coli O104:H4 induced haemolytic uraemic syndrome.

DESIGN

Multicentre retrospective case-control study.

SETTING

23 hospitals in northern Germany.

PARTICIPANTS

298 adults with enterohaemorrhagic E coli induced haemolytic uraemic syndrome.

MAIN OUTCOME MEASURES

Dialysis, seizures, mechanical ventilation, abdominal surgery owing to perforation of the bowel or bowel necrosis, and death.

RESULTS

160 of the 298 patients (54%) temporarily required dialysis, with only three needing treatment long term. 37 patients (12%) had seizures, 54 (18%) required mechanical ventilation, and 12 (4%) died. No clear benefit was found from use of plasmapheresis or plasmapheresis with glucocorticoids. 67 of the patients were treated with eculizumab, a monoclonal antibody directed against the complement cascade. No short term benefit was detected that could be attributed to this treatment. 52 patients in one centre that used a strategy of aggressive treatment with combined antibiotics had fewer seizures (2% v 15%, P = 0.03), fewer deaths (0% v 5%, p = 0.029), required no abdominal surgery, and excreted E coli for a shorter duration.

CONCLUSIONS

Enterohaemorrhagic E coli induced haemolytic uraemic syndrome is a severe self limiting acute condition. Our findings question the benefit of eculizumab and of plasmapheresis with or without glucocorticoids. Patients with established haemolytic uraemic syndrome seemed to benefit from antibiotic treatment and this should be investigated in a controlled trial.

[Characteristics of acute intestinal infection process and evaluation of pathogenetic therapy efficacy]

Characteristics of the clinical process of acute intestinal infection were studied. The main infection was salmonellosis. The intoxication syndrome was defined and its dynamics was estimated by the intoxication leukocytic index. The severity and intoxication syndrome level were characterized by the integral value or the level of the mean mass molecules. The infusion validity as pathogenetic treatment providing detoxication and normal hemostasis was shown. The favourable outcomes were observed to depend on the dynamics of the main clinical symptoms and the intoxication leukocytic index.

Differential effect of inhibiting MD-2 and CD14 on LPS- versus whole E. coli bacteria-induced cytokine responses in human blood

BACKGROUND

Sepsis is a major world-wide medical problem with high morbidity and mortality. Gram-negative bacteria are among the most important pathogens of sepsis and their LPS content is regarded to be important for the systemic inflammatory reaction. The CD14/myeloid differentiation factor 2 (MD-2)/TLR4 complex plays a major role in the immune response to LPS . The aim of this study was to compare the effects of inhibiting MD-2 and CD14 on ultra-pure LPS - versus whole E. coli bacteria-induced responses.

METHODS

Fresh human whole blood was incubated with upLPS or whole E. coli bacteria in the presence of MD-2 or CD14 neutralizing monoclonal antibodies, or their respective controls, and/or the specific complement-inhibitor compstatin. Cytokines were measured by a multiplex (n = 27) assay. NFκB activity was examined in cells transfected with CD14, MD-2 and/or Toll-like receptors.

RESULTS

LPS-induced cytokine response was efficiently and equally abolished by MD-2 and CD14 neutralization. In contrast, the response induced by whole E. coli bacteria was only modestly reduced by MD-2 neutralization, whereas CD14 neutralization was more efficient. Combination with compstatin enhanced the effect of MD-2 neutralization slightly. When compstatin was combined with CD14 neutralization, however, the response was virtually abolished for all cytokines, including IL-17, which was only inhibited by this combination. The MD-2-independent effect observed for CD14 could not be explained by TLR2 signaling.

CONCLUSION

Inhibition of CD14 is more efficient than inhibition of MD-2 on whole E. coli-induced cytokine response, suggesting CD14 to be a better target for intervention in Gram-negative sepsis, in particular when combined with complement inhibition.

Activated protein C protects vascular endothelial cells from apoptosis in malaria and in sepsis

OBJECTIVE

In malaria and sepsis, apoptotic endothelial damage is preventable in vitro by antioxidants and protease inhibitors. Activated protein C, which has anti-apoptotic effects, improves survival in sepsis. Therefore, we studied whether activated protein C prevents endothelial cell apoptosis, induced by serum from patients with malaria or sepsis.

METHODS

Endothelial cells were incubated with patient sera (Plasmodium falciparum malaria, Escherichia coli sepsis, Staphylococcus aureus sepsis) or culture supernatants of the respective organisms, with or without neutrophils. Activated protein C was used to reduce endothelial cell apoptosis in vitro. The proportion of apoptotic endothelial cells was determined by TUNEL staining.

RESULTS

The apoptosis-inducing effect of patient sera or culture supernatants (P. falciparum, E. coli, S. aureus) on endothelial cells was augmented by neutrophils and reduced by activated protein C in the presence of neutrophils. Pre-incubating either endothelial cells or neutrophils with activated protein C also reduced the endothelial cell apoptosis rate. The pro-apoptotic effect of P. falciparum supernatant was reduced by pan-caspase inhibitor and caspase 8 inhibitor, but not by caspase 9 inhibitor. The pro-apoptotic effect of E. coli and S. aureus supernatants was also reduced by caspase 9 inhibitor.

CONCLUSIONS

Activated protein C protects vascular endothelial cells from apoptosis triggered by patient sera or culture supernatants in combination with neutrophils. It seems to act both on neutrophils and on endothelial cells. Activated protein C blocks caspase-8-dependent apoptosis, which accounts for endothelial damage in sepsis and malaria. Therefore, activated protein C might offer clinical benefit not only in sepsis but also in malaria.

Relationship between time to positivity of blood culture with clinical characteristics and hospital mortality in patients with Escherichia coli bacteremia

BACKGROUND

Previous studies indicated that the time to positivity (TTP) of blood culture is a parameter correlating with degree of the bacteremia and outcome in patients with bloodstream infections caused by Escherichia coli (E. coli). The objective of this study was to further investigate the diagnostic and prognostic power of using TTP to predict E. coli bacteremia.

METHODS

A retrospective cohort study at two university hospitals was conducted. We retrieved all the medical records of those with E. coli bloodstream infection according to the records generated by their microbiology departments. Univariate and multivariate analyses were applied to identify clinical factors correlating with fast bacterial growth and significant prognostic factors for hospital mortality.

RESULTS

Medical records of 353 episodes of E. coli bacteremia diagnosed between January 1, 2007 and December 31, 2009 were retrieved in the investigation. Univariate analysis demonstrated that the TTP ≤ 7 hours group is associated with higher incidence of active malignancies (41.7% vs. 27.2%, P = 0.010), neutropenia (30% vs.14.3%, P = 0.007), primary bacteremia (55.0% vs. 33.4%, P = 0.002), and poorer outcome (hospital mortality 43.3% vs.11.9%, P = 0.000) than the TTP > 7 hours group. Multivariate analysis revealed that the significant predictors of hospital mortality, in rank order from high to low, were TTP (for TTP ≤ 7 hours, odds ratio (OR): 4.886; 95% confidence interval (CI): 2.572 - 9.283; P = 0.000), neutropenia (OR: 2.800; 95%CI: 1.428 - 5.490; P = 0.003), comedication of steroids or immunosuppressive agents (OR: 2.670; 95%CI: 0.971 - 7.342; P = 0.057).

CONCLUSIONS

Incidence of malignancies, neutropenia and primary bacteremia correlates with fast bacterial growth in patients with E. coli bacteremia. The parameter of TTP has been identified as a variable of highest correlation to hospital mortality and therefore can be potentially utilized as a mortality prognostic marker.

[Antibiotic resistance of bacterial strains isolated from bacteremias in immuno-compromised patients]

Immunocompromised hosts are subjects of predilection to bloodstream infections. The global mortality is high. Bacterial strains are frequently multiresistant; fungemias are almost always deadly, in spite of the susceptibility of the fungus.

OBJECTIVE

to evaluate the positive blood cultures in patients with malignant and non-malignant diseases and to determine the resistance mechanisms with the Vitek2.

MATERIAL AND METHOD

a 29 months study--181 episodes of invasive infections--168 patients. The blood culture vials were Bactec Plus. The isolates were identified using Api galleries and with the Vitek 2. The susceptibility was tested by the disk-diffusion method (Oxoid Ltd.). Minimal inhibitory concentrations: Vitek2.

INTERPRETATION

EUCAST 2008 standard.

RESULTS

overall mortality: 27%. Gram-negative bacilli: 59.4% and 48.5% Gram-positive cocci. Klebsiella pneumoniae and Escherichia coli isolates accounted for 16.43% and 71.23%respectively; 25% of E. coli strains and 33% of K. pneumoniae respectively, produced extended-spectrum beta-lactamases. Oxacillin resistance: 54.4% of S. aureus isolates. No resistance to carbapenems in enterobacteria.

CONCLUSIONS

Bacterial resistance is not likely to decrease, if at all; Death produced by infections is an event that can be prevented. Molecular determinations should be performed to assess the role of the virulence genes and of the resistance mechanisms and to help the better understanding of the interractions between bacteria and the human organism.