Isolation and detection of Shiga toxin-producing Escherichia coli in clinical stool samples using conventional and molecular methods.

The isolation of Shiga toxin-producing Escherichia coli (STEC) other than serogroup O157 from clinical stool samples is problematic due to the lack of differential phenotypic characteristics from non-pathogenic E. coli. The development of molecular reagents capable of identifying both toxin and serogroup-specific genetic determinants holds promise for a more comprehensive characterization of stool samples and isolation of STEC strains. In this study, 876 stool samples from paediatric patients with gastroenteritis were screened for STEC using a cytotoxicity assay, commercial immunoassay and a conventional PCR targeting Shiga-toxin determinants. In addition, routine culture methods for isolating O157 STEC were also performed. The screening assays identified 45 stools presumptively containing STEC, and using non-differential culture techniques a total of 20 O157 and 22 non-O157 strains were isolated. These included STEC serotypes O157 : H7, O26 : H11, O121 : H19, O26 : NM, O103 : H2, O111 : NM, O115 : H18, O121 : NM, O145 : NM, O177 : NM and O5 : NM. Notably, multiple STEC serotypes were isolated from two clinical stool samples (yielding O157 : H7 and O26 : H11, or O157 : H7 and O103 : H2 isolates). These data were compared to molecular serogroup profiles determined directly from the stool enrichment cultures using a LUX real-time PCR assay targeting the O157 fimbrial gene lpfA, a microsphere suspension array targeting allelic variants of espZ and a gnd-based molecular O-antigen serogrouping method. The genetic profile of individual stool cultures indicated that the espZ microsphere array and lpfA real-time PCR assay could accurately predict the presence and provide preliminary typing for the STEC strains present in clinical samples. The gnd-based molecular serogrouping method provided additional corroborative evidence of serogroup identities. This toolbox of molecular methods provided robust detection capabilities for STEC in clinical stool samples, including co-infection of multiple serogroups.

Thinking ecologically for safer healthcare: a summer research student partnership.

As leaders for nursing education, nursing research, healthcare administration and patient safety, we asked one another: How do we use our collective resources to build health system capacity for clinically based research training and safer healthcare? Drawing on knowledge from the field of ecological restoration, which is the study and repair of damaged ecosystems, we partnered the Safer Systems research program of the Faculty of Nursing, University of Alberta, with Capital Health's Royal Alexandra Hospital (RAH), the Caritas Health Group, the Canadian Patient Safety Institute (CPSI) and several funding agencies to provide hands-on training in clinical research, infection control and patient safety policy development for nursing students during the summer months. As we plan ahead, our student and staff evaluations show that together, we can make concrete, vital contributions to student education, nursing research, evidence-informed practice, clinical quality improvement and national policy. We are using what we have learned to continually expand the range of undergraduate, graduate and post-doctoral clinical learning opportunities in healthcare safety that are available year round. Our shared goal is to support current and future nurses in leading the way for safer healthcare systems and the safest possible healthcare.

Regulation of vascular tone during pregnancy: a novel role for the pregnane X receptor.

During pregnancy, maternal vascular function is altered through mechanisms that remain unclear. Progesterone synthesis and metabolism are also increased. Progesterone metabolites are potent endogenous ligands for the pregnane X receptor (PXR), a nuclear receptor that induces the expression of hepatic cytochrome P450 enzymes. Cytochrome P450 enzymes located in the vasculature can metabolize arachidonic acid to produce epoxyeicosatrienoic acids, known vasodilators. We hypothesized that PXR is present in vascular tissue and contributes to vascular adaptations to pregnancy. PXR mRNA was detected in mouse mesenteric arteries by quantitative RT-PCR. Constrictor and relaxation responses in wildtype (PXR(+/+)) and PXR-deficient (PXR(-/-)) mice were compared by wire myography. Relative to nonpregnant controls, arteries from pregnant PXR(+/+) mice had reduced sensitivity to phenylephrine-induced constriction (EC(50): 2.77+/-0.32 mumol/L versus 5.13+/-0.36 mumol/L; P=0.009) and enhanced maximal vasorelaxation to bradykinin (26+/-3% versus 44+/-16%; P=0.013). However, these pregnancy adaptations were absent in PXR(-/-) mice. We also hypothesized that PXR is activated by progesterone metabolites. Treatment of PXR(+/+) and PXR(-/-) nonpregnant mice with 5beta-dihydroprogesterone for 7 days enhanced endothelium-dependent relaxation in only the PXR(+/+) mice, similarly to that seen in pregnancy. In treated mice, inhibition of cytochrome P450 epoxygenase activity with N-methylsulphonyl-6-(2-propargyloxyphenyl)hexanamide attenuated vasorelaxation in arteries from PXR(+/+) but not PXR(-/-) mice. We conclude that PXR contributes to the development of vascular adaptations to pregnancy, likely in response to activation by progesterone metabolites, and that PXR-dependent increases in vasorelaxation may be because of activation of cytochrome P450 epoxygenases.