Direct susceptibility testing by disk diffusion on clinical samples : a rapid and accurate tool for antibiotic stewardship

We compared the accuracy of direct susceptibility testing (DST) with conventional antimicrobial susceptibility testing (AST), both using disk diffusion, on clinical samples. A total of 123 clinical samples (respiratory tract samples, urine, vaginal and abdominal abscess discharges, bile fluid and a haematoma punctate) were selected on various indications; direct inoculation on Mueller-Hinton agar and antibiotic paper disks were applied. In parallel, standard culture, identification and AST on the colonies grown overnight was executed. Both AST and DST were interpreted after identification of the isolates. The results from both AST and DST for 11 antibiotics tested on 97 samples with Gram-negative rods showed 93.4 % total agreement, 1.6 % minor discordances, 4.6 % major discordances and 0.4 % very major discordances. Analysing the discordant results, DST predominantly resulted in more resistant isolates than AST. This was mostly due to the presence of resistant mutants or an additional isolate. The remaining discordances were seen for isolates with inhibition zones close to the clinical breakpoint. For the 26 samples yielding staphylococci, a total agreement of 100 % was observed for the nine antibiotics tested. Overall, the highest percentage of discordant results occurred for the beta-lactam antibiotics amoxicillin-clavulanate (13.4 %) and cefuroxime (12.4 %). When used selectively and interpreted carefully, DST on clinical samples is potentially very useful in the management of critically ill patients, as the time to results is shortened by approximately 24 h. However, we recommend to communicate results with reservations and confirm by conventional AST

Apparent digestibility in meat-type guinea pigs as determined by total collection or by internal marker

Six adult male meat-type guinea pigs were subjected to three subsequent digestibility trials with 100% alfalfa, 50% alfalfa and 50% sugar cane and 50% alfalfa and 50% concentrate. For each animal in each period, feed intakes were recorded and all faeces were collected and stored at -20 degrees C until analysis. Feeds and faeces were analysed for dry matter, crude ash, crude protein, ether-extract, crude fibre and acid-insoluble ash. Coefficients of apparent digestibility were calculated according to both the total collection method and the marker method with acid-insoluble ash as internal marker. The present study suggests that acid-insoluble ash is not valid as an internal marker when looking at differences between individuals, but might be useful to demonstrate differences between diets, albeit with lack of accuracy for estimating the absolute digestibility coefficients obtained through the total collection method. Sugar cane was slightly less digestible than alfalfa in meat-type guinea-pigs

Discussion on the figures of merit of identified traps located in the Si film : surface versus volume trap densities

The aim of this work is a discussion on the figures of merit of identified traps located in the depletion zone (Si film) of advanced MOSFET devices. Two methodologies to estimate the volume trap densities are investigated, one using the relationship between the surface trap density and volume trap density and a second one based on the temperature evolution at fixed frequency of the generation-recombination plateau level associated to the same trap. By comparing the volume trap densities estimated using these two methods, the results are not agreeing with each other, suggesting that these methods can no longer be used with accuracy in multigate devices. Moreover, they may lead in certain cases to results physically not correct. Even about of the volume defects, the linear evolution between the plateau and the characteristic frequency of the generation-recombination contributions associated to the same trap give us the surface trap density without any additional assumption

Comparison of four serological assays for the diagnosis of Chlamydia trachomatis in subfertile women

Introduction: Chlamydia antibody testing (CAT) in serum has been introduced as a screening method in the infertility workup. We evaluated the test characteristics of two ELISA tests compared to micro-immunofluorescence tests (MIFs). MIFs are considered the gold standard in the C. trachomatis IgG antibodies detection. We also compared the accuracy of all CAT tests in predicting tubal subfertility, using laparoscopy as a reference. Methodology: Four commercial serological methods were used to analyse 101 serum samples for the presence of C. trachomatis IgG antibodies from patients at the Infertility Clinic of Ghent University Hospital. The diagnostic utility for prediction of tubal infertility of serological methods was evaluated based on patients' medical records. Results: A comparison of the serological assays showed little difference in the major performance characteristics: the sensitivities of all MIFs and ELISAs were 100% for all assays (except the ELISA Vircell, with a sensitivity of 90%), and the specificities ranged from 92% for MIF Ani Labsystems to 98% for the MIF Focus and ELISA Vircell. As compared to laparoscopy data, CAT positivity in subfertile women with tubal damage (n=40) did not significantly differ from that of subfertile women without tubal damage (n=61): Positive predictive values (PPV) of CAT ranged from 53% to 60% and negative predictive values (NPV) ranged from 62% to 64%. Conclusion: evaluated ELISAs are comparable to MIFs in the detection of C. trachomatis IgG antibodies and should be preferred for large serological studies, especially in resource poor settings

Optimal Power Flow in Four-Wire Distribution Networks: Formulation and Benchmarking

In recent years, several applications have been proposed in the context of distribution networks. Many of these can be formulated as an optimal power flow problem, a mathematical optimization program which includes a model of the steady-state physics of the electricity network. If the network loading is balanced and the lines are transposed, the network model can be simplified to a single-phase equivalent model. However, these assumptions do not apply to low-voltage distribution networks, so the network model should model the effects of phase unbalance correctly. In many parts of the world, the low-voltage distribution network has four conductors, i.e. three phases and a neutral. This paper develops OPF formulations for such networks, including transformers, shunts and voltage-dependent loads, in two variable spaces, i.e. current-voltage and power-voltage, and compares them for robustness and scalability. A case study across 128 low-voltage networks also quantifies the modelling error introduced by Kron reductions and its impact on the solve time. This work highlights the advantages of formulations in current-voltage variables over power-voltage, for four-wire networks.Comment: 10 pages, submitted to Power Systems Computation Conference 202

Healthcare-associated bloodstream infections in a neonatal intensive care unit over a 20-year period (1992-2011) : trends in incidence, pathogens, and mortality

Objective. To analyze trends in the incidence and pathogen distribution of healthcare-associated bloodstream infections (HABSIs) over a 20-year period (1992-2011). Design. Historical cohort study. Setting. Thirty-two-bed neonatal intensive care unit (NICU) in a tertiary referral hospital. Patients. Neonates with HABSIs defined according to the criteria of the National Institute of Child Health and Development (NICHD). Methods. A hospital-based ongoing surveillance program was used to identify HABSI cases in neonates. A distinction between definite or possible HABSI was made according to the NICHD criteria. Incidence, incidence densities (HABSIs per 1,000 hospital-days and HABSIs per 1,000 total parenteral nutrition-days), and case fatality rate were calculated. Logistic regression analysis was used to find time trends. Four periods of 5 years were considered when executing variance analysis. Results. In total, 682 episodes of HABSIs occurred on 9,934 admissions (6.9%). The median total incidence density rate was 3.1 (interquartile range, 2.2-3.9). A significant increasing time trend in incidence density was observed for the period 1995-2011 (P < .003). A significant decrease in the case fatality rate was found in the last 5-year period (P < .001). No neonate died following possible HABSIs, whereas the case fatality rate among neonates with definite HABSIs was 9.7%. Most HABSIs were caused by coagulase-negative staphylococci (n = 414 [60.7%]). A significant increase in Staphylococcus aureus HABSI was observed in the last 10-year period (P < .001). Conclusions. An increase in incidence density rate occurred, while the case fatality rate dropped. Better perinatal care could be responsible for the latter. A decrease in days before infection and a high incidence of coagulase-negative Staphylococcus HABSIs indicate the need for vigorous application of evidence-based prevention initiatives, in particular for catheter care

Scanning Electron Microscopy of Dentin Caries. Experimental in vitro Studies with Streptococcus Mutans

This study was performed to gain better insight into the mechanisms involved in carious destruction of human dentin by Streptococcus mutans. In particular, bacterial colonization of dentin surfaces and bacterial invasion in dentin were studied. Streptococcus mutans (S. mutans), strain NCTC 10449, was grown on sterile dentin blocks in a 10% CO2 atmosphere at 37°C. After 72, 120, 144 and 288 h of incubation the specimens were processed for scanning electron microscopic examination. The colonization of the dentinal surface progressed slowly and was nearly complete after 288 h. Invasion of S. mutans into the dentinal tubules was found occasionally and was limited to the initial 5 μm of the tubular lumen. The acid metabolites produced by S. mutans, caused lesions of the dentinal structures in the close proximity of the bacteria. From the results of this in vitro study it appears that carious destruction of exposed dentinal surfaces by S. mutans mainly occurs at the exposed dentin after it has been colonized by bacteria. Destruction of the deeper dentinal layers by bacteria invading the dentinal tubules may play a less important role. However, in the few cases where S. mutans invaded the dentinal tubules, rapid destruction of the peritubular dentin sheath occurred. In addition, the possibility remains that acid metabolites produced by S. mutans diffuse into the dentinal tubules and cause tissue damage in the deeper parts of the dentin