Ab initio spectroscopic characterization of the radical CH3_3OCH2_2 at low temperatures

Spectroscopic and structural properties of methoxymethyl radical (CH$_3$OCH$_2$, RDME) are determined using explicitly correlated ab initio methods. This radical of astrophysical and atmospheric relevance has not been fully characterized at low temperatures, which has delayed the astrophysical searches. We provide rovibrational parameters, excitations to the low energy electronic states, torsional and inversion barriers and low vibrational energy levels. In the electronic ground state (X$^2$A), which appears "clean" from non-adiabatic effects, the minimum energy structure is an asymmetric geometry which rotational constants and dipole moment have been determined to be A$_0$=46718.6745 MHz, B$_0$=10748.4182 MHz, and C$_0$=9272.5105 MHz, and 1.432 D ($\mu_A$=0.6952 D, $\mu_B$=1.215 D, $\mu_C$=0.3016 D), respectively. A variational procedure has been applied to determine torsion-inversion energy levels. Each level splits into 3 subcomponents (A$_1$/A$_2$ and E) corresponding to the three methyl torsion minima. Although the potential energy surface presents 12 minima, at low temperatures, the infrared band shapes correspond to a surface with only three minima because the top of the inversion V$^{\alpha}$ barrier at ${\alpha}=0^{\circ}$ (109 cm$^{-1}$) stands below the zero point vibrational energy and the CH$_2$ torsional barrier is relatively high ($\sim$2000 cm$^{-1}$). The methyl torsion barrier was computed to be $\sim$500 cm$^{-1}$ and produces a splitting of 0.01 cm$^{-1}$ of the ground vibrational state

Spectrum of external catheter-related infections in children with acute leukemia—Single-center experience

AbstractBackgroundExternal catheters (ECs) are commonly used in children who are receiving treatment for acute leukemia.AimsTo study the spectrum of microorganisms and to compare the rates of infection.MethodsA total of 42 ECs were inserted, including 28 Port-A-Caths, 11 CVC lines and 3 Hickman lines. Single ECs were required for 19 patients (45.2%), whereas 2, 3 and 4 ECs were required in 8, 1 and 1 patients, respectively.ResultsOverall, 37 culture-documented infections were present in 18 (62%) patients who had ECs. Gram-positive microorganisms were identified in 20 cases, Gram-negative microorganisms in 14 cases and fungal infections in 3 cases. Of the 42 devices implanted, 10 out of 28 Port-A-Caths (35.7%), 2 out of 3 Hickman catheters (66.7%) and 9 out of 11 central venous catheters (81.8%) required removal due to infection. The average length of working life for the ports was 330.6 days (range: 40–1043 days). The median rate of complications due to infection was 2.84 infections per 1000 catheter days (interquartile range: −1.55 to 5.8), and the number of infections was correlated with the number of ports (Pearson's r=0.51; p<0.05)

Pediatric Staphylococcus aureus Bacteremia: Clinical Spectrum and Predictors of Poor Outcome

Background Staphylococcus aureus is a common cause of bacteremia, yet the epidemiology and predictors of poor outcome remain inadequately defined in childhood. Methods ISAIAH (Invasive Staphylococcus aureus Infections and Hospitalizations in children) is a prospective, cross-sectional study of S. aureus bacteremia (SAB) in children hospitalized in Australia and New Zealand over 24 months (2017–2018). Results Overall, 552 SABs were identified (incidence 4.4/100 000/year). Indigenous children, those from lower socioeconomic areas and neonates were overrepresented. Although 90-day mortality was infrequent, one-third experienced the composite of: length of stay >30 days (26%), intensive care unit admission (20%), relapse (4%), or death (3%). Predictors of mortality included prematurity (adjusted odds ratio [aOR],16.8; 95% confidence interval [CI], 1.6–296.9), multifocal infection (aOR, 22.6; CI, 1.4–498.5), necrotizing pneumonia (aOR, 38.9; CI, 1.7–1754.6), multiorgan dysfunction (aOR, 26.5; CI, 4.1–268.8), and empiric vancomycin (aOR, 15.7; CI, 1.6–434.4); while infectious diseases (ID) consultation (aOR, 0.07; CI .004–.9) was protective. Neither MRSA nor vancomycin trough targets impacted survival; however, empiric vancomycin was associated with nephrotoxicity (OR, 3.1; 95% CI 1.3–8.1). Conclusions High SAB incidence was demonstrated and for the first time in a pediatric setting, necrotizing pneumonia and multifocal infection were predictors of mortality, while ID consultation was protective. The need to reevaluate pediatric vancomycin trough targets and limit unnecessary empiric vancomycin exposure to reduce poor outcomes and nephrotoxicity is highlighted. One in 3 children experienced considerable SAB morbidity; therefore, pediatric inclusion in future SAB comparator trials is paramount to improve outcomes

Whole genome sequencing and molecular epidemiology of paediatric Staphylococcus aureus bacteraemia

Objectives The role Staphylococcus aureus antimicrobial resistance genes and toxins play in disease severity, management and outcome in childhood is an emerging field requiring further exploration. Methods A prospective multisite study of Australian and New Zealand children hospitalised with S. aureus bacteraemia (SAB) occurred over 24 months (2017–2018). Whole genome sequencing (WGS) data were paired with clinical information from the ISAIAH cohort. Results 353 SAB isolates were sequenced; 85% methicillin-susceptible S. aureus ([MSSA], 301/353) and 15% methicillin-resistant S. aureus ([MRSA], 52/353). There were 92 sequence types (STs), most commonly ST5 (18%) and ST30 (8%), grouped into 23 clonal complexes (CCs), most frequently CC5 (21%) and CC30 (12%). MSSA comprised the majority of healthcare-associated SAB (87%, 109/125), with principal clones CC15 (48%, 11/21) and CC8 (33%, 7/21). Panton-Valentine leukocidin (PVL)-positive SAB occurred in 22% (76/353); predominantly MSSA (59%, 45/76), community-onset (92%, 70/76) infections. For community-onset SAB, the only microbiological independent predictor of poor outcomes was PVL positivity (aOR 2.6 [CI 1.0–6.2]). Conclusion From this WGS paediatric SAB data, we demonstrate the previously under-recognized role MSSA has in harbouring genetic virulence and causing healthcare-associated infections. PVL positivity was the only molecular independent predictor of poor outcomes in children. These findings underscore the need for further research to define the potential implications PVL-producing strains may have on approaches to S. aureus clinical management