RESUMO
Knowledge surveys are a type of confidence survey in which students rate their confidence in their ability to answer questions rather than answering the questions. These surveys have been discussed as a tool to evaluate student in-class or curriculum-wide learning. However, disagreement exists as to whether confidence is actually an accurate measure of knowledge. With the concomitant goals of assessing content-based learning objectives and addressing this disagreement, we present herein a pretest/posttest knowledge survey study that demonstrates a significant difference correctness on graded test questions at different levels of reported confidence in a multi-semester timeframe. Questions were organized into Bloom's taxonomy, allowing for the data collected to further provide statistical analyses on strengths and deficits in various levels of Bloom's reasoning with regard to mean correctness. Collectively, students showed increasing confidence and correctness in all levels of thought but struggled with synthesis-level questions. However, when students were only asked to rate confidence and not answer the accompanying test questions, they reported significantly higher confidence than the control group which was asked to do both. This indicates that when students do not attempt to answer questions, they have significantly greater confidence in their ability to answer those questions. Additionally, when students rate only confidence without answering the question, resolution across Bloom's levels of reasoning is lost. Based upon our findings, knowledge surveys can be an effective tool for assessment of both breadth and depth of knowledge, but may require students to answer questions in addition to rating confidence to provide the most accurate data.
RESUMO
Most diagnostic approaches for Shiga toxin producing Escherichia coli (STEC) have been designed to detect only serogroup O157 that causes a majority, but not all STEC related outbreaks in the United States. Therefore, there is a need to develop methodology that would enable the detection of other STEC serogroups that cause disease. Three bacteriophages (phages) that infect STEC serogroups O26, O103, O111, O145 and O157 were chemically labeled with horseradish peroxidase (HRP). The enzyme-labeled phages (Phazymes) were individually combined with a sampling device (a swab), STEC serogroup-specific immunomagnetic separation (IMS) beads, bacterial enrichment broth and luminescent HRP substrate, in a self-contained test device, while luminescence was measured in a hand-held luminometer.The O26 and O157 Phazyme assays correctly identified more than 93% of the bacteria tested during this study, the O123 Phazyme assay identified 89.6%, while the O111 and O145 Phazyme assays correctly detected 82.4% and 75.9%, respectively. The decreased specificity of the O111 and O145 assays was related to the broad host ranges of the phages used in both assays. The Phazyme assays were capable of directly detecting between 10(5) and 10(6) CFU/ml in pure culture, depending on the serogroup. In food trials, the O157 Phazyme assay was able to detect E. coli O157:H7 in spinach consistently at levels of 1 CFU/g and occasionally at levels of 0.1 CFU/g. The assay detected 10(0) CFU/100 cm(2) on swabbed meat samples and 10(2) CFU/100 ml in water samples. The Phazyme assay effectively detects most STEC in a simple and rapid manner, with minimal need for instrumentation to interpret the test result.
