Prevalence of enterohaemorrhagic Escherichia coli from serotype O157 and other attaching and effacing Escherichia coli on bovine carcasses in Algeria

AIMS: Bovine meat is the principal source of human contamination of attaching and effacing Escherichia coli, including enterohaemorrhagic E. coli O157. The aim was to study the prevalence of these strains on bovine carcasses in Algeria. METHODS AND RESULTS: Two-hundred and thirty carcasses were swabbed and analysed by classical microbiological methods for total E. coli counts and for the presence of pathogenic E. coli. The E. coli counts were high, with a 75th percentile of 444.75 CFUs cm(-2). For pathogenic E. coli, more than 7% of the tested carcasses were positive for E. coli O157. Eighteen E. coli O157 strains were isolated and typed by multiplex PCR. The main isolated pathotype (78%) was eae+ stx2+ ehxA+. In addition to E. coli O157, other attaching and effacing E. coli (AEEC) were also detected from carcasses by colony hybridization after pre-enrichment and plating on sorbitol MacConkey agar using eae, stx1 and stx2 probes. Thirty carcasses (13%) on the 230 analysed harboured at least one colony positive for one of the tested probes. These positive carcasses were different from those positive for E. coli O157. Sixty-six colonies (2.9%) positive by colony hybridization were isolated. The majority (60.6%) of the positive strains harboured an enteropathogenic E. coli-like pathotype (eae+ stx-). Only three enterohaemorrhagic E. coli (EHEC)-like (eae+ stx1+) colonies were isolated from the same carcass. These strains did not belong to classical EHEC serotypes. CONCLUSIONS: In this study, the global hygiene of the slaughterhouse was low, as indicated by the high level of E. coli count. The prevalence of both E. coli O157 and other AEEC was also high, representing a real hazard for consumers. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study of this type in Algeria, which indicates that the general hygiene of the slaughterhouse must be improved.     

Identification of biomarker panels as predictors of severity in coronary artery disease

Matrix metalloproteinases (MMPs) are implicated in atherosclerotic plaque rupture and recondition. Specific tissue inhibitors (TIMPs) control MMP functions. Both MMPs and TIMPs are potential biomarkers of plaque instability. Elevated Apo-CII and CIII and Apo-E levels are recognized as cardiovascular disease risk factors. We aimed to establish the best blood biomarker panel to evaluate the coronary artery disease (CAD) severity. Plasma levels of MMP-3 and MMP-9, TIMP-1 and TIMP-2, Apo-CII, Apo-CIII and Apo-E were measured in 472 patients with CAD evaluated by coronary angiography and electrocardiography, and in 285 healthy controls. MMP-3 and MMP-9 plasma levels in CAD patients were significantly increased (P < 0.001) compared to controls (3.54- and 3.81-fold, respectively). Furthermore, these increments are modulated by CAD severity as well as for Apo-CII and Apo-CIII levels (P < 0.001). TIMPs levels were decreased in CAD versus controls (P < 0.001) and in inverse correlation to MMPs. Standard ROC curve approach showed the importance of panels of biomarkers, including MMP-3, MMP-9, TIMP-1, TIMP-2, Apo-CII and Apo-CIII, for disease aggravation diagnosis. A high area under curve (AUC) value (0.995) was reached for the association of MMP-9, TIMP-2 and Apo-CIII. The unbalance between MMPs and TIMPs in vascular wall and dyslipidaemia creates favourable conditions for plaque disruption. Our study suggests that the combination of MMP-9, TIMP-2 and Apo-CIII values (‘CAD aggravation panel’) characterizes the severity of CAD, that is electrophysiological state, number of involved vessels, stent disposal and type of stent.     

Inhibition of the Differentiation of Monocyte-Derived Dendritic Cells by Human Gingival Fibroblasts

We investigated whether gingival fibroblasts (GFs) can modulate the differentiation and/or maturation of monocyte-derived dendritic cells (DCs) and analyzed soluble factors that may be involved in this immune modulation. Experiments were performed using human monocytes in co-culture with human GFs in Transwell® chambers or using monocyte cultures treated with conditioned media (CM) from GFs of four donors. The four CM and supernatants from cell culture were assayed by ELISA for cytokines involved in the differentiation of dendritic cells, such as IL-6, VEGF, TGFβ1, IL-13 and IL-10. The maturation of monocyte-derived DCs induced by LPS in presence of CM was also studied. Cell surface phenotype markers were analyzed by flow cytometry. In co-cultures, GFs inhibited the differentiation of monocyte-derived DCs and the strength of this blockade correlated with the GF/monocyte ratio. Conditioned media from GFs showed similar effects, suggesting the involvement of soluble factors produced by GFs. This inhibition was associated with a lower stimulatory activity in MLR of DCs generated with GFs or its CM. Neutralizing antibodies against IL-6 and VEGF significantly (P<0.05) inhibited the inhibitory effect of CM on the differentiation of monocytes-derived DCs and in a dose dependent manner. Our data suggest that IL-6 is the main factor responsible for the inhibition of DCs differentiation mediated by GFs but that VEGF is also involved and constitutes an additional mechanism.     

A novel sesquiterpene lactone from Centaurea pullata: structure elucidation, antimicrobial activity, and prediction of pharmacokinetic properties

A novel elemanolide with an alpha-methyl-gamma-lactone moiety, 8alpha-O-(4-hydroxy-2-methylenebutanoyloxy)melitensine, in addition to four known sesquiterpene lactones also bearing the same lactone ring, melitensin, 11beta,13 dihydrosalonitenolide, 8alpha-hydroxy-11beta,13-dihydro-4-epi-sonchucarpolide, and 8alpha-hydroxy-11beta,13-dihydro-onopordaldehyde have been isolated from the aerial parts of Centaurea pullata. The in vitro antibacterial and antifungal activities of the isolated sesquiterpene lactones were tested against six bacteria and eight fungal species, using a microdilution method. All compounds tested showed greater antibacterial and antifungal activities than the positive controls used. Moreover, the pharmacokinetic profile of these compounds was investigated using computational methods.     

PTGS2 (COX-2) −765 G > C functional promoter polymorphism and its association with risk and lymph node metastasis in nasopharyngeal carcinoma

Cyclooxygenase-2 (Cox-2) is a key enzyme in the conversion of arachidonic acid to prostaglandins that has been shown to have a particular importance in the progression of several malignancies including nasopharyngeal carcinoma (NPC). In the current report, we designed a case-controlled study to evaluate the susceptibility and prognostic implications of the functional −765 G > C genetic variation in NPC. A PCR and restriction fragment length polymorphism analysis was used to determine the polymorphism in a Tunisian population of patients with NPC (n = 180) and in healthy control subjects (n = 169). A higher risk for NPC was observed for carriers of COX-2 −765 C allele (OR = 1.76; P = 0.01). This association remains significant after adjustments for age and sex (OR = 1.89; P = 0.008). Regarding prognostic indicators, a significant association was found between −765 C allele carriers and the presence of lymph node metastasis (OR = 2.28; P = 0.01), as well as, with tumor stage (OR = 2.73; P = 0.03). This is the first report on the studies of COX-2 SNPs in NPC and our data suggest that this genetic variant may play a role in mediating susceptibility to NPC, as well as, in neoplastic progression, a finding which further supports the involvement of COX-2 in NPC etiology. Hela Ben Nasr and Karim Chahed contributed equally to the study.     

Differential regulation of endoplasmic reticulum stress by protein tyrosine phosphatase 1B and T cell protein tyrosine phosphatase

Protein-tyrosine phosphatase 1B (PTP1B) and T cell protein-tyrosine phosphatase (TCPTP) are closely related intracellular phosphatases implicated in the control of glucose homeostasis. PTP1B and TCPTP can function coordinately to regulate protein tyrosine kinase signaling, and PTP1B has been implicated previously in the regulation of endoplasmic reticulum (ER) stress. In this study, we assessed the roles of PTP1B and TCPTP in regulating ER stress in the endocrine pancreas. PTP1B and TCPTP expression was determined in pancreases from chow and high fat fed mice and the impact of PTP1B and TCPTP over- or underexpression on palmitate- or tunicamycin-induced ER stress signaling assessed in MIN6 insulinoma β cells. PTP1B expression was increased, and TCPTP expression decreased in pancreases of mice fed a high fat diet, as well as in MIN6 cells treated with palmitate. PTP1B overexpression or TCPTP knockdown in MIN6 cells mitigated palmitate- or tunicamycin-induced PERK/eIF2α ER stress signaling, whereas PTP1B deficiency enhanced ER stress. Moreover, PTP1B deficiency increased ER stress-induced cell death, whereas TCPTP deficiency protected MIN6 cells from ER stress-induced death. ER stress coincided with the inhibition of Src family kinases (SFKs), which was exacerbated by PTP1B overexpression and largely prevented by TCPTP knockdown. Pharmacological inhibition of SFKs ameliorated the protective effect of TCPTP deficiency on ER stress-induced cell death. These results demonstrate that PTP1B and TCPTP play nonredundant roles in modulating ER stress in pancreatic β cells and suggest that changes in PTP1B and TCPTP expression may serve as an adaptive response for the mitigation of chronic ER stress.     

Hole Transporting Bilayers for Efficient Micrometer-Thick Perovskite Solar Cells

Achieving high efficiencies in halide perovskite solar cells with thicknesses >1 µm is necessary for developing perovskite-Si tandem cells based on small pyramidal structures. To achieve this goal, not only is the perovskite layer quality to be optimized but also the properties of the charge-transport layers must be tuned to reduce charge-collection losses. The transport layers provide a non-ohmic resistance that modulates the Fermi-level splitting inside the perovskite absorber. The finite conductivity of the transport layers can lead to losses in the fill factor (FF) and short-circuit current, even at infinite charge-carrier mobility in the absorber layer. These losses notably scale with the absorber layer thickness, which implies that higher-conductivity transport layers are required for thicker perovskite absorbers. One strategy to improve charge collection and thereby FFs in thick inverted perovskite solar cells is to use bilayers of hole-transport layers. In this study, the combination of poly[bis(4-phenyl) (2,4,6-trimethylphenyl)amine] with self-assembled monolayers provides the best photovoltaic performance in single-junction devices.     

Antiprotozoal activity of magnesium oxide (MgO) nanoparticles against Cyclospora cayetanensis oocysts

Outbreaks of Cyclospora cayetanensis infection have been linked to consumption of food and water contaminated by oocysts that can survive both physical and chemical disinfectants. Magnesium oxide (MgO) nanoparticles (NPs) can be potentially used in food as bactericides. In this study, C. cayetanensis pre- and post-sporulated oocysts were exposed to MgO NPs with different doses ranging from 1.25–25?mg/ml. With comparison to control, the antiprotozoal activity of MgO NPs was evaluated by identifying the median effective concentration dose (EC₅₀), lethal concentration dose (LC₉₀), microscopically changes on treated oocysts and rates of sporulation. Among pre- and post-sporulated oocysts, MgO NPs?≥?EC₅₀ was observed after 24?h at concentrations 10 and 12.5?mg/ml, respectively, while?≥?LC₉₀ was observed after 24?h, 48?h and 72?h at concentrations 15, 12.5 and 10?mg/ml, respectively. MgO NPs treated oocysts showed abnormal morphological changes such as an increase in size, wall injury, deposition of vacuolated homogenous particles in the cytoplasm, evacuation of oocyst's contents, and collapse. Sporocysts of treated oocysts were noticed to be peripherally shifted. Sporulation failure of treated oocysts achieved ≥90% after 24?h and 72?h of incubation with 15 and 12.5?mg/ml, respectively, while it was 10.1% among non-treated. All the differences were statistically significant. Our results demonstrated that MgO NPs has a significant anti-Cyclospora effect on both unsporulated and sporulated oocysts, especially considering that it could be biologically synthesized, that way it can be used safely as a preventive agent in food and water disinfectant treatment.