A European perspective on intravascular catheter-related infections: report on the microbiology workload, aetiology and antimicrobial susceptibility (ESGNI-005 Study)

The laboratory workload, microbiological techniques and aetiology of catheter-related infections in European hospitals are mostly unknown. The present study (ESGNI-005) comprised a 1-day (22 October 2001), laboratory-based, point-prevalence survey based on a questionnaire completed by microbiology laboratories in European (European Union (EU) and non-EU) hospitals. Also included were questions requesting retrospective information for the year 2000. In total, 151 hospitals from 26 European countries participated, of which 78.1% were teaching institutions. Overall, the estimated population served by these institutions was 121,363,800, and the estimated number of admissions during 2000 was 6,712,050. The total number of catheter tips processed during 2000 was 142,727, or 21/1,000 admissions, of which 23.7% were considered to be positive in the institutions using semiquantitative or quantitative techniques. Overall, EU centres received significantly more catheter tip samples/1,000 admissions and had a significantly higher rate of 'positivity' (p < 0.0001) than non-EU centres. Of the institutions surveyed, 11.4% (7.2% in EU countries and 23.7% in non-EU countries; p 0.04) used only qualitative techniques for catheter tip sample processing. On the day of the study, 167 microorganisms were recovered from significant catheter tip cultures (122 patients), of which Gram-positive bacteria represented 70.7%, Gram-negative bacteria 22.2%, and yeasts 7.2%. The five most common microorganisms were coagulase-negative staphylococci, Staphylococcus aureus, Candida spp., Enterococcus spp. and Pseudomonas spp. Overall, 19% of catheter tip cultures were polymicrobial. In the case of S. aureus, 40% of isolates were resistant to oxacillin, as were 63.4% of coagulase-negative staphylococcus isolates. Of 37 Gram-negative isolates, 35% were resistant to cefotaxime, 31% to ceftazidime, and 27% to ciprofloxacin. Imipenem and cefepime had the lowest reported rates of resistance (11%).     

Thalamic atrophy in patients with pure hereditary spastic paraplegia type 4

Journal of Neurology - SPG4 is an autosomal dominant pure form of hereditary spastic paraplegia (HSP) caused by mutations in the SPAST gene. HSP is considered an upper motor neuron disorder...     

Tracking of regions-of-interest in myocardial contrast echocardiography

Analysis of intramyocardial perfusion by contrast echocardiography provides quantitative parameters for the assessment of ischemic disease. This analysis can be achieved by applying an ultrasound (US) burst of high mechanical index to destroy contrast bubbles, measuring various myocardial refilling parameters from the time curves obtained from regions-of-interest (ROIs) within the myocardial wall. To obtain reliable intensity curves, the position of the ROIs must be tracked to compensate for the heart motion along the sequence. In this work, we studied the use of optical flow techniques for ROI repositioning. Two block-matching and one differential technique were evaluated for this purpose. Performance was measured by comparing the result of automatic tracking with results of ROI repositioning by a human expert. This evaluation was carried out on experimental data from animals as well as on sequences from clinical studies. Results are considered to be accurate enough for clinical purposes, and computation times may allow for a real-time processing if incorporated into a US scanner.     

Cerebral blood flow is an earlier indicator of perfusion abnormalities than cerebral blood volume in Alzheimer's disease

The purpose of this study was to elucidate whether cerebral blood flow (CBF) can better characterize perfusion abnormalities in predementia stages of Alzheimer''s disease (AD) than cerebral blood volume (CBV) and whether cortical atrophy is more associated with decreased CBV or with decreased CBF. We compared measurements of CBV, CBF, and mean cortical thickness obtained from magnetic resonance images in a group of healthy controls, patients with mild cognitive impairment (MCI) who converted to AD after 2 years of clinical follow-up (MCI-c), and patients with mild AD. A significant decrease in perfusion was detected in the parietal lobes of the MCI-c patients with CBF parametric maps but not with CBV maps. In the MCI-c group, a negative correlation between CBF values and cortical thickness in the right parahippocampal gyrus suggests an increase in CBF that depends on cortical atrophy in predementia stages of AD. Our study also suggests that CBF deficits appear before CBV deficits in the progression of AD, as CBV abnormalities were only detected at the AD stage, whereas CBF changes were already detected in the MCI stage. These results confirm the hypothesis that CBF is a more sensitive parameter than CBV for perfusion abnormalities in MCI-c patients.     

Augmented acquisition of cocaine self-administration and altered brain glucose metabolism in adult female but not male rats exposed to a cannabinoid agonist during adolescence.

Marijuana consumption during adolescence has been proposed to be a stepping-stone for adult cocaine addiction. However, experimental evidence for this hypothesis is missing. In this work we chronically injected male and female Wistar rats with either the cannabinoid agonist CP 55,940 (CP; 0.4 mg/kg) or its corresponding vehicle. Adult acquisition (seven 30 min daily sessions) and maintenance (fourteen 2 h daily sessions) of cocaine self-administration (1 mg/kg), food-reinforced operant learning under conditions of normal (ad libitum access to food), and high motivation (food-restriction schedule) were measured. Additionally, brain metabolic activity was analyzed by means of [(18)F]-fluorodeoxyglucose positron emission tomography. During the acquisition phase, female CP-treated rats showed a higher rate of cocaine self-administration as compared to vehicle-treated females and males; no differences were found between both male groups. This effect disappeared in the maintenance phase. Moreover, no differences among groups were evident in the food-reinforced operant task, pointing to the cocaine-specific nature of the effect seen in self-administration rather than a general change in reward processing. Basal brain metabolic activity also changed in CP-treated females when compared to their vehicle-treated counterparts with no differences being found in the males; more specifically we observed a hyper activation of the frontal cortex and a hypo activation of the amygdalo-entorhinal cortex. Our results suggest that a chronic exposure to cannabinoids during adolescence alters the susceptibility to acquire cocaine self-administration, in a sex-specific fashion. This increased susceptibility could be related to the changes in brain metabolic activity induced by cannabinoids during adolescence.     

Multimodal neuroimaging studies and neurodevelopment and neurodegeneration hypotheses of schizophrenia

The interpretation of the huge number of results in schizophrenia research using neuroimaging is uncertain. However, the simultaneous use of complimentary data obtained with these techniques may yield more relevant information in this regard. In this paper we present a series of studies performed by our group in two schizophrenic samples with the use of structural (magnetic resonance imaging, MRI), functional [glucose positron emission tomography (PET) and N-acetyl-aspartate (NAA) magnetic resonance spectrocopy] and neurophysiological techniques (the P300 event-related potential). Transversal and longitudinal measurements were performed.The integrated vision of the results so obtained allows us to propose the hypothesis of a neurodevelopmentally determined state of prefrontal disinihibition, in which the degree of atrophy would directly relate to the metabolic rate. This state would already be present in the first stages of illness and could have neurotoxic consequences in the long term. This would explain the findings of an association between sulcal cerebrospinal fluid (CSF) and illness duration and decreased NAA levels in chronic but not in recent-onset cases. The prefrotnal disinhibition would overstimulate the limbic system and the hippocampus would become overactivated, the metabolic rate at this level being inversely related to P300 amplitude. Clozapine showed a more selective and intense action on that hyperactive metabolic tone than haloperidol.     

Statistical parametric mapping (SPM) in nuclear medicine

In the scope of medical research, functional neuroimaging analysis permits the study of pathological or cognitive cerebral processes by using statistical quantification techniques. A tool of increasing use is the SPM (Statistical Parametric Mapping) software due to its wide availability and the variety of statistical studies that can be made. Nevertheless, being unaware of the theoretical background on which it is based may easily lead to inaccurate results and even to the reaching of erroneous conclusions. The present article summarizes these theoretical principles and discusses the main key points of the method without requiring advanced mathematical knowledge.     

P300 amplitude as a possible correlate of frontal degeneration in schizophrenia

The existence of neurodegeneration is a debated issue in schizophrenia research. The P300 component of event-related electrical potentials (ERP) has been related to the different degree of damage to gray and white matter. This study explores the possible relationship between P300 amplitude and/or latency and the existence of degenerative processes in schizophrenia, by assessing its correlation with volume of sulcal CSF and duration of illness, as transversal indicators of neurodegeneration. Nineteen patients (14 males, 5 females) and 13 controls (6 males, 7 females) were studied with MRI and electrophysiological records (P300). The possible influence of sex and age at the time of the exploration was statistically controlled in both groups. The results show a significant negative correlation between P300 amplitude and prefrontal CSF volume in the patient group. A lower though still significant correlation was also found between P300 amplitude and duration of illness, whereas no correlation was found in the control group. These results support the hypothesis that P300 amplitude may be interpreted as a marker of neurodegeneration in schizophrenia.     

Unsupervised estimation of myocardial displacement from tagged MR sequences using nonrigid registration.

We propose a fully automatic cardiac motion estimation technique that uses nonrigid registration between temporally adjacent images to compute the myocardial displacement field from tagged MR sequences using as inputs (sources) both horizontally and vertically tagged images. We present a new multisource nonrigid registration algorithm employing a semilocal deformation model that provides controlled smoothness. The method requires no segmentation. We apply a multiresolution optimization strategy for better speed and robustness. The accuracy of the algorithm is assessed on experimental data (animal model) and healthy volunteer data by calculating the root mean square (RMS) difference in position between the estimated tag trajectories and manual tracings outlined by an expert. For the approximately 20000 tag lines analyzed (45 slices over 20-40 time frames), the RMS difference between the automatic tag trajectories and the manually segmented tag trajectories was 0.51 pixels (0.25 mm) for the animal data and 0.49 pixels (0.49 mm) for the human volunteer data. The RMS difference in the separation between adjacent tag lines (RMS_TS) was also assessed, resulting in an RMS_TS of 0.40 pixels (0.19 mm) in the experimental data and 0.52 pixels (0.56 mm) in the volunteer data. These results confirm the subpixel accuracy achieved using the proposed methodology.