Dynamic Behavior of Thermally Affected Injection-Molded High-Density Polyethylene Parts Modified by Accelerated Electrons.

Polyethylenes are the most widely used polymers and are gaining more and more interest due to their easy processability, relatively good mechanical properties and excellent chemical resistance. The disadvantage is their low temperature stability, which excludes particular high-density polyethylenes (HDPEs) for use in engineering applications where the temperature exceeds 100 °C for a long time. One of the possibilities of improving the temperature stability of HDPE is a modification by accelerated electrons when HDPE is cross-linked by this process and it is no longer possible to process it like a classic thermoplastic, e.g., by injection technology. The HDPE modified in this way was thermally stressed five times at temperatures of 110 and 160 °C, and then the dynamic tensile behavior was determined. The deformation and surface temperature of the specimens were recorded by a high-speed infrared camera. Furthermore, two thermal methods of specimen evaluation were used: differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The result of the measurement is that the modification of HDPE by accelerated electrons had a positive effect on the dynamic tensile behavior of these materials.

[Risk factors for methicillin-resistant Staphylococcus aureus bacteremia: A multicenter matched case-control study].

INTRODUCTION: Methicillin-resistant Staphylococcus aureus is a frequent pathogen at critical care services. Its presence leads to increased hospital stays and mortality risk in patients with bacteremia. However, the etiology of this resistance marker has not been fully studied. OBJECTIVE: To identify risk factors associated with the emergence of methicillin-resistant S. aureus bacteremia in critically ill patients treated at intensive care units in Bogotá, Colombia. MATERIALS AND METHODS: We conducted a retrospective paired case-control study, nested in a cohort of patients diagnosed with S. aureus bacteremia and treated at intensive care units between 2006 and 2008 in Bogotá. Cases were patients with positive blood culture to methicillin resistance, matched in a 1:1 ratio with methicillin-sensitive controls isolated from the same institution and hospitalization year. We used conditional logistic regression to analyze the risk factors associated with the presence of resistance, with emphasis on prior antibiotic therapy. RESULTS: We included 372 patients with S. aureus bacteremia. Factors such as the use of pre-hospital devices: vascular (OR=1.986, 95% CI 1.038 to 3.801) and urinary (OR=2.559, 95% CI: 1.170 to 5.596), along with the number of previously used antibiotics, were associated with the emergence of resistance. The number of antibiotics used previously was determined to have a gradient effect, particularly carbapenems. CONCLUSIONS: The rational use of antibiotics and surveillance of exposure to surgical procedures or use of invasive devices are interventions that could diminish the emergence of methicillin-resistant S. aureus bacteremia causes.

Frequency of microorganisms isolated in patients with bacteremia in intensive care units in Colombia and their resistance profiles

OBJECTIVE: The aim of this study was to describe the most frequently found bacterial microorganisms in bloodstream isolates taken from patients in intensive care units in Colombia and their resistance profiles. METHODS: This was a multicentre descriptive observational study that was carried out between January 2001 and June 2008 with laboratory data from 33 participating hospitals in a surveillance network. RESULTS: The most frequently found microorganisms were coagulase-negative Staphylococci 39.6%, Staphylococcus aureus 12.3%, Klebsiella pneumoniae 8.2%, Escherichia coli 5.7%, Acinetobacter baumannii, 4.0% and Pseudomonas aeruginosa 3.8%. Coagulase-negative Staphylococci registered greater than 70% oxacillin resistance rate. S. aureus presented a change in its multiresistance profile during the years of follow-up. There was a trend towards a lower resistance rate among E. coli and K. pneumoniae isolates during the study period while A. baumannii carbapenem resistance rate exceeded 50%. DISCUSSION: There has been a change in the frequency of species being isolated with a higher frequency of enterobacteriaceae compared to Gram-positive microorganisms, in general with a high resistance rate.