Background Carbapenem resistance among gram-negative bacilli is an emerging threat worldwide. The objective of this study was to identify risk factors for the acquisition of carbapenem-resistant ...Escherichia coli (CRE). Methods We conducted a matched case-control study comprising 57 cases of acquisition of CRE and 114 controls (1:2 matched) selected from patients with a culture of carbapenem-susceptible E coli between January 2006 and December 2010 at a 2000-bed tertiary care center in South Korea. Results On univariate analysis, previous use of carbapenem ( P < .01), fluoroquinolone ( P < .01), and glycopeptide ( P < .01), as well as length of hospital stay ( P < .05), were significantly associated with CRE acquisition. On multivariate analysis, previous use of carbapenem (odds ratio OR, 4.56; 95% confidence interval CI 1.44-14.46; P = .01) and previous use of fluoroquinolone (OR, 2.81; 95% CI, 1.14-6.99; P = .03) were independent risk factors. Conclusions At this institute, the antibiotic selective pressure of carbapenems and fluoroquinolones was shown to be an important risk factor for the acquisition of CRE.
A process model was developed to simulate the generation of ethanol or acetic acid by selectively using syngas from coke oven gas as the carbon source. The simulation involved three reactors: the ...first reactor converts syngas into dimethyl ether over a hybrid Cu/ZnO/Al
2
O
3
/ferrierite catalyst; in the second reactor, carbonylation of dimethyl ether to methyl acetate takes place. The kinetic parameters for the carbonylation reaction were estimated by fitting the model to the experimental results. The third reactor uses the hydrogenation or hydrolysis of the methyl acetate to selectively synthesize ethanol or acetic acid, respectively. In the integrated process, a recycling loop was introduced, and its effects on the conversion, carbon molar yield, energy consumption, and capital and utility costs were evaluated. The results show that the recycling loop could enhance the carbon molar yield by approximately 20 times compared to that in the open-loop case owing to the high overall conversion (91–97%) of dimethyl ether in the second reactor.
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•Reforming reaction was studied on Ni/Al2O3 treated with organic acids using coke oven gas.•Ni/Al2O3 with formic acid showed a higher activity by maintaining smaller nickel ...particles.•Acids changed the γ-Al2O3 surface charge by forming strong metal-support interaction.•Kinetic parameters using Langmuir–Hinshelwood–Hougen–Watson mechanism (LHHW) were derived.
Combined steam and carbon dioxide reforming with CH4 (CSCR) has been investigated using Ni/Al2O3 catalysts, where γ-Al2O3 support was previously modified with four different organic acids before nickel impregnation, to verify the effects of different nickel distributions induced from the modified acid sites to the catalytic activity. The CSCR reactions were performed at T=750°C, P=1.0MPa, space velocity of 36,000L(total mixed gas)/(kgcat·h), and CH4/CO2/CO/H2/H2O molar ratio=1/0.38/0.29/2.09/1.2, which is the typical compositions of the coke oven gas in steel industry. The Ni/Al2O3 prepared by formic acid for the pretreatment of γ-Al2O3 showed a higher catalytic activity due to the maintenance of smaller nickel particles even after a high temperature CSCR reaction. The types of organic acids significantly changed the surface properties of γ-Al2O3 by varying the isoelectric points, which are strongly depending on pKa values of organic acids, and it concomitantly alters the dispersion of nickel precursor with the different deposition depths in γ-Al2O3 pores by largely changing the particle size distribution and the metal-support interaction. The surface-enriched nickel containing Ni/Al2O3 pretreated with oxalic acid was also applied to derive the kinetic parameters using Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism by showing an activation energy of ∼240kJ/mol for the CSCR reaction.
The effects of reaction parameters, including reaction temperature and space velocity, on hydrogen production via steam reforming of methane (SRM) were investigated using lab- and bench-scale ...reactors to identify critical factors for the design of large-scale processes. Based on thermodynamic and kinetic data obtained using the lab-scale reactor, a series of SRM reactions were performed using a pelletized catalyst in the bench-scale reactor with a hydrogen production capacity of 10 L/min. Various temperature profiles were tested for the bench-scale reactor, which was surrounded by three successive cylindrical furnaces to simulate the actual SRM conditions. The temperature at the reactor bottom was crucial for determining the methane conversion and hydrogen production rates when a sufficiently high reaction temperature was maintained (>800 °C) to reach thermodynamic equilibrium at the gas-hourly space velocity of 2.0 L CH4/(h·gcat). However, if the temperature of one or more of the furnaces decreased below 700 °C, the reaction was not equilibrated at the given space velocity. The effectiveness factor (0.143) of the pelletized catalyst was calculated based on the deviation of methane conversion between the lab- and bench-scale reactions at various space velocities. Finally, an idling procedure was proposed so that catalytic activity was not affected by discontinuous operation.
Objective. To compare the characteristics and risk factors for surgical site infections (SSIs) after total hip arthroplasty (THA) and total knee arthroplasty (TKA) in a nationwide survey, using ...shared case detection and recording systems.
Design. Retrospective cohort study.
Setting. Twenty-six hospitals participating in the Korean Nosocomial Infections Surveillance System (KONIS).
Patients. From 2006 to 2009, all patients undergoing THA and TKA in KONIS were enrolled.
Results. SSI occurred in 161 (2.35%) of 6,848 cases (3,422 THAs and 3,426 TKAs). Pooled mean SSI rates were 1.69% and 2.82% for THA and TKA, respectively. Of the cases we examined, 42 (26%) were superficial-incisional SSIs and 119 (74%) were “severe” SSIs; of the latter, 24 (15%) were deep-incisional SSIs and 95 (59%) were organ/space SSIs. In multivariate analysis, a duration of preoperative hospital stay of greater than 3 days was a risk factor for total SSI after both THA and TKA. Diabetes mellitus, revision surgery, prolonged duration of surgery (above the 75th percentile), and the need for surgery due to trauma were independent risk factors for total and severe SSI after THA, while male sex and an operating room without artificial ventilation were independent risk factors for total and severe SSI after TKA. A large volume of surgeries (more than 10 procedures per month) protected against total and severe SSI, but only in patients who underwent TKA.
Conclusions. Risk factors for SSI after arthroplasty differ according to the site of the arthroplasty. Therefore, clinicians should take into account the site of arthroplasty in the analysis of SSI and the development of strategies for reducing SSI.
•Fe-based Fischer–Tropsch synthesis was conducted in a pilot-scale reactor.•Kinetic model was developed with kinetic parameters estimated using experimental data.•A two-dimensional reactor model with ...radial dispersion was considered.•Effects of tube diameter on the conversion and the thermal behavior were evaluated.
The present work describes the development of a two-dimensional mathematical model of a pilot-scale fixed-bed reactor for Fe-based Fischer–Tropsch synthesis to evaluate the effect of tube diameter on temperature profile and catalyst performance. The entire chain lengths of the hydrocarbon products were lumped to form several representative components, and the apparent kinetic parameters for the reaction rates were estimated. The effectiveness of the developed model was corroborated by the comparison of temperature profiles, conversion, and selectivities between experimental and simulated results. The increase of tube diameter in the simulation showed that temperature increased in both the radial and the axial directions owing to the low radial heat transfer rate and the low heat transfer area, respectively. Finally, the specified diameter in the present study maintained the temperature below the threshold value and the methane selectivity below 10%.
HIV-associated neurocognitive disorder (HAND) can occur in patients without prior AIDS defining illness and can be debilitating. This study aimed to evaluate the difference in the patterns of ...intrinsic brain activity between patients with or without HAND for deepening our understanding of HAND.
We evaluated 24 HIV-infected individuals, 12 with previously diagnosed HAND and 12 previously diagnosed without HAND, and 11 seronegative individuals. These individuals then underwent repeat NP testing and a functional brain MRI scan. For functional MRI analysis, seed-based analysis with bilateral precuneus cortex seed was applied.
Among the 12 individuals with previously diagnosed HAND, 3 showed improvement of their neurocognitive function and 1 was excluded for worsening liver disease. Among the 12 patients who previously had normal neurocognitive function, 2 showed neurocognitive impairment. Overall, the HAND group, who had impaired cognitive function at the time of MRI scan, showed significant decrease of resting status functional connectivity between bilateral precuneus and prefrontal cortex (PFC) compared with nonHAND group, those who had normal neurocognitive function (Corrected P<0.05). The functional connectivity with the right inferior frontal operculum and right superior frontal gyrus was positively correlated with memory and learning ability.
This cross-sectional study found a significant difference in fMRI patterns between patients with and without HAND. Decreased functional connectivity between precuneus and PFC could be possible functional substrate for cognitive dysfunction in HIV patients, which should be characterized in a longitudinal study.
The first human immunodeficiency virus (HIV) infection was reported in Korea in 1985. The number of HIV-infected persons domestically increased in the 1990s showing epidemic indigenousization. Since ...then, the number of new infections gradually increased every year, and recently more than 1,000 newly infected cases were reported per year. A total of 12,522 infected individuals have been reported up to 2015, of which 2,020 died. The male to female ratio was 15.4:1, and 34.2% of them were under 30 years old. The infection route was homosexual and bisexual contact in 60.1% of cases and heterosexual contact in 34.6% of cases. Candidiasis, Pneumocystis pneumonia, tuberculosis were common as a AIDS (acquired immune deficiency syndrome)-defining illness. But with the introduction of antiretroviral therapy in the late 1990s, non-AIDS defining illnesses such as metabolic complications, cardiovascular diseases, bone diseases, and neuropsychiatric disorders such as neurocognitive dysfunction, depression, and anxiety are emerging as new health problems. The management policy switched its focus from regulating and monitoring of HIV-infected persons to ensuring access to treatment and promotion of voluntary HIV testing in high-risk groups. Also as the age of the infected persons increases, a need for various supports such as social rehabilitation, life counseling, and welfare has emerged.
Several studies have evaluated the impact of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) combined with antimicrobial stewardship in patients with ...positive blood cultures; clinical outcomes improved. However, in many hospitals, antimicrobial stewardship is not available because of restricted medical resources. Thus, we investigated the impact of evaluation by MALDI-TOF MS on the clinical outcomes of patients with bacteremia and fungemia treated in a clinical setting lacking an antimicrobial stewardship program (ASP).
We designed a pre-post quasi experimental study and retrospectively reviewed the medical records of patients aged > 18 years old with bacteremia and fungemia during two periods: October-December 2012 and October-December 2013. Conventional methods were used to detect microbial pathogens in 2012, and MALDI-TOF MS was employed in 2013. Clinical outcomes compared between periods were the time to pathogen identification, time to effective therapy, 30-day all-cause mortality, time to microbiological clearance, length of ICU stay, and rate of recurrence of the same bloodstream infection (BSI).
A total of 556 patients were enrolled; 302 patients in 2012, and 254 in 2013. The use of MALDI-TOF MS without an ASP reduced the time to pathogen identification (86.4 vs. 63.5 h, P < 0.001) but did not significantly reduce the time to effective therapy (27.4 vs. 23.2 h, P = 0.187). Also, none of the following differed significantly between the two periods: mortality (17.5 vs. 15.7%, P = 0.571), the time to microbiological clearance (3.6 vs. 3.7 days, P = 0.675), the length of ICU stay (16.8 vs. 14.7 days, P = 0.706), and the recurrence rate of the same BSI (5.0 vs. 2.8%, P = 0.183).
The use of MALDI-TOF MS alone in a setting lacking an ASP did not afford clinical benefits. An ASP combined with MALDI-TOF MS is necessary to improve clinical outcomes.
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