SCC-DFTB parameters for simulating hybrid gold-thiolates compounds.

We present a parametrization of a self-consistent charge density functional-based tight-binding scheme (SCC-DFTB) to describe gold-organic hybrid systems by adding new Au-X (X = Au, H, C, S, N, O) parameters to a previous set designed for organic molecules. With the aim of describing gold-thiolates systems within the DFTB framework, the resulting parameters are successively compared with density functional theory (DFT) data for the description of Au bulk, Aun gold clusters (n = 2, 4, 8, 20), and Aun SCH3 (n = 3 and 25) molecular-sized models. The geometrical, energetic, and electronic parameters obtained at the SCC-DFTB level for the small Au3 SCH3 gold-thiolate compound compare very well with DFT results, and prove that the different binding situations of the sulfur atom on gold are correctly described with the current parameters. For a larger gold-thiolate model, Au25 SCH3 , the electronic density of states and the potential energy surfaces resulting from the chemisorption of the molecule on the gold aggregate obtained with the new SCC-DFTB parameters are also in good agreement with DFT results.

Enterococci increase the morbidity and mortality associated with severe intra-abdominal infections in elderly patients hospitalized in the intensive care unit.

OBJECTIVES: Enterococci may increase morbidity and mortality in elderly patients with intra-abdominal infections (IAIs) hospitalized in the intensive care unit (ICU). PATIENTS AND METHODS: A single-centre, retrospective evaluation of an ICU database (1997-2007) of elderly ICU patients (≥75 years) with a severe IAI was performed. Demographics, severity scores, underlying diseases, microbiology and outcomes were recorded. Patients with enterococci isolated in peritoneal fluid (E+ group) were compared with those lacking enterococci in peritoneal fluid (E- group). Stepwise multivariate logistic regression was used to identify independent factors associated with mortality. RESULTS: One hundred and sixty patients were included (mean ±â€ŠSD age 82 ±â€Š5 years; n = 72 in the E+ group). The E+ group was more severely ill than the E- group, with higher Simplified Acute Physiologic Score 2 (61 ±â€Š20 versus 48 ±â€Š16, P = 0.0001) and Sequential Organ Failure Assessment scores (8 ±â€Š3 versus 5 ±â€Š3, P = 0.0001), a greater postoperative infection rate (58.3% versus 34.1%, P = 0.01), a higher incidence of inappropriate empirical antimicrobial therapies (33.3% versus 19.3%, P = 0.04), a longer duration of mechanical ventilation (11.8 ±â€Š10.9 versus 7.8 ±â€Š10.2 days, P = 0.02) and greater vasopressor use (7.2 ±â€Š7.1 versus 3.3 ±â€Š4.1 days, P = 0.001). ICU mortality was higher in the E+ group than in the E- group (54.2% versus 38.6%, P = 0.05). In the multivariate analysis, E+ status was independently associated with mortality (odds ratio 2.24; 95% confidence interval 1.06-4.75; P = 0.03). CONCLUSIONS: In severely ill, elderly patients in the ICU for an IAI, the isolation of enterococci was associated with increased disease severity and morbidity and was an independent risk factor for mortality.