The stealth episome: suppression of gene expression on the excised genomic island PPHGI-1 from Pseudomonas syringae pv. phaseolicola

Pseudomonas syringae pv. phaseolicola is the causative agent of halo blight in the common bean, Phaseolus vulgaris. P. syringae pv. phaseolicola race 4 strain 1302A contains the avirulence gene avrPphB (syn. hopAR1), which resides on PPHGI-1, a 106 kb genomic island. Loss of PPHGI-1 from P. syringae pv. phaseolicola 1302A following exposure to the hypersensitive resistance response (HR) leads to the evolution of strains with altered virulence. Here we have used fluorescent protein reporter systems to gain insight into the mobility of PPHGI-1. Confocal imaging of dual-labelled P. syringae pv. phaseolicola 1302A strain, F532 (dsRFP in chromosome and eGFP in PPHGI-1), revealed loss of PPHGI-1::eGFP encoded fluorescence during plant infection and when grown in vitro on extracted leaf apoplastic fluids. Fluorescence-activated cell sorting (FACS) of fluorescent and non-fluorescent PPHGI-1::eGFP F532 populations showed that cells lost fluorescence not only when the GI was deleted, but also when it had excised and was present as a circular episome. In addition to reduced expression of eGFP, quantitative PCR on sub-populations separated by FACS showed that transcription of other genes on PPHGI-1 (avrPphB and xerC) was also greatly reduced in F532 cells harbouring the excised PPHGI-1::eGFP episome. Our results show how virulence determinants located on mobile pathogenicity islands may be hidden from detection by host surveillance systems through the suppression of gene expression in the episomal state

Improving the Physical Diagnosis Skills of Third-year Medical Students: A Controlled Trial of a Literature-based Curriculum

OBJECTIVE: To determine if a literature-based physical diagnosis curriculum could improve student knowledge, skill, and self-confidence in physical diagnosis. DESIGN: Prospective controlled trial of an educational intervention. SETTING: Required internal medicine clerkship for third-year medical students at Brown Medical School. PARTICIPANTS: Third-year medical students who completed the internal medicine clerkship during the academic year 1999–2000: 32 students at 1 clerkship site received the intervention; a total of 50 students at 3 other clerkship sites served as controls. INTERVENTION: Physical diagnosis curriculum based on 8 articles from the Journal of the American Medical Association's Rational Clinical Examination series. Intervention students met weekly for 1 hour with a preceptor to review each article, discuss the sensitivity and specificity of the maneuvers and findings, and practice the techniques with an inpatient who agreed to be visited and examined. MEASUREMENTS AND MAIN RESULTS: Physical diagnosis knowledge for the 8 topics was evaluated using a 22-item multiple choice question quiz, skill was evaluated using trained evaluators, and self-confidence was assessed using an end-of-clerkship survey. Intervention students scored significantly higher than the control group on the knowledge quiz (mean correct score 70% vs 63%, P = .002), skills assessment (mean correct score 90% vs 54%, P < .001), and self-confidence score (mean total score 40 vs 35, P = .003), and they expressed greater satisfaction with the physical diagnosis teaching they received in the clerkship. CONCLUSION: This physical diagnosis curriculum was successful in improving students' knowledge, skill, and self-confidence in physical diagnosis

A Bedside Clinical Prediction Rule for Detecting Moderate or Severe Aortic Stenosis

OBJECTIVE: To evaluate a bedside clinical prediction rule for detecting moderate or severe aortic stenosis. DESIGN: Cross-sectional study with independent comparison to a diagnostic reference standard, doppler echocardiography. SETTING: Urban university hospital. PARTICIPANTS: Consecutive hospital inpatients (n = 124) who had been referred for echocardiography. MEASUREMENTS AND MAIN RESULTS: Participants were examined by a third-year general internal medicine resident and a staff general internist. We hypothesized in advance that absence of a murmur over the right clavicle would rule out aortic stenosis, while the presence of three or four associated findings (slow carotid artery upstroke, reduced carotid artery volume, maximal murmur intensity at the second right intercostal space, and reduced intensity of the second heart sound) would rule in aortic stenosis. Study physicians were unaware of echocardiographic findings. The outcome was echocardiographic moderate or severe aortic stenosis, defined as a valve area of 1.2 cm(2)or less, or a peak instantaneous gradient of 25 mm Hg or greater. Absence of a murmur over the right clavicle ruled out aortic stenosis (likelihood ratio [LR] 0.10; 95% confidence interval [CI] 0.01, 0.44). The presence of three or four associated findings ruled in aortic stenosis (LR 40; 95% CI 6.6, 240). If a murmur was present over the right clavicle, but no more than two associated findings were present, then the examination was indeterminate (LR 1.8; 95% CI 0.93, 2.9). CONCLUSION: A clinical prediction rule, using simple bedside maneuvers, accurately ruled in and ruled out aortic stenosis