The major aims of this study were to estimate the infection rate and recognize the risk factor for ventriculoperitoneal (VP) shunt infections in children. To analyze shunt infection rate and identify risk factors, a retrospective cohort analysis of 333 consecutive VP shunt series was performed at Seoul National University Children's Hospital in Korea between January 2005 and February 2011. Overall, 35 shunts (10.5%) were infected, which represented an infection rate of 0.075 infection cases per shunt per year. VP shunt infection occurred at a median of 1 month (range, 6 days to 8 months) after insertion. An independent risk factor for shunt infection was undergoing an operation before the first year of life (relative risk 2.31; 95% confidence interval, 1.19-4.48). The most common causative microorganism was coagulase-negative staphylococci in 16 (45.7%) followed by Staphylococcus aureus in 8 (22.9%). Methicillin resistance rate was 83.3% among coagulase-negative staphylococci and S. aureus. In this study, cerebrospinal fluid shunt infection rate was 10.5%. Infection was frequently caused by methicillin-resistant coagulase-negative staphylococci and S. aureus within two months after shunt surgery. Vancomycin may be considered as the preoperative prophylaxis for shunt surgery in a situation where methicillin resistance rate is very high.

The parameters determining the set state current and reset voltage, determined by the strength of formed filaments, were examined using current pulse and voltage driven current-voltage ͑I-V͒ sweeps. In the pulse switching measurement, the total current flow, including overshooting noise effect at the moment of set switching, was found to determine the strength of the filament. Displacing the capacitive charge dissipation peak from the overshoot region by a longer pulse rising time was effective in reducing the random variations in the switching parameters. A smaller voltage step in the I-V sweep was effective in reducing the random variation in filament formation.Resistance switching ͑RS͒ phenomena in a variety of thin-film materials have recently attracted considerable attention for applications to the next generation of nonvolatile memory devices. 1-3 The unipolar RS proceeds by applying the same bias polarity and has been understood from the formation and rupture of the percolated conduction channels ͓conducting filaments ͑CFs͔͒ in several binary oxides, e.g., TiO 2 and NiO. 2,3 In the filamentary RS, improvement of the switching uniformity should be accomplished for memory device fabrication. One of the reasons for the nonuniform RS comes from the random nature of filament formation. Filament formation, accompanied by oxygen ion movement in most cases, is a very disordered process. [4][5][6] This results in the fluctuations of various switching parameters, such as the switching voltage and on and off currents. The other reason originated from the distortion of the stimulus signal for initiating RS. In pulse switching, input pulse distortion by the overshoot effect due to a short pulse rising time can cause a nonuniform RS. This article reports a method to overcome the overshoot effect on the set switching by using a current pulse with a longer rising time. In addition, in the voltage sweep switching, which is another common switching method, a smaller voltage step during the set switching reduced the random variation significantly.The preparation of a Pt/60 nm thick TiO 2 /Pt structured sample and a method for the RS of the sample are reported in detail elsewhere. 7,8 A current pulse pattern generator ͑PG, HP/Agilent 81110A͒ with various pulse rising ͑also falling͒ times ͑t r ͒ was used as a current pulse source for the first type of set switching experiments. The transient current at the moment of set switching using the PG was monitored using a digital oscilloscope ͑OSC, Tektronix 684C͒. For this current monitoring, the internal resistance of PG was set to 1 k⍀. The PG was programmed to obtain a peak current of 50 mA at the OSC considering the on-state resistance of the sample ͑ ϳ15 ⍀͒ and the internal resistance of the OSC ͑50 ⍀͒. A schematic diagram for the pulse switching setup is shown in the inset of Fig. 1f. Here, the monitored voltage in OSC ͑V R ͒ was converted into the sample current using the resistance of the OSC. For the second type of set switching experiments, a semiconductor parameter analyze...

Purpose : This study was performed to identify the etiologic agents and antimicrobial susceptibility patterns of organisms responsible for bloodstream infections in pediatric cancer patients for guidance in empiric antimicrobial therapy. Methods : A 5-year retrospective study of pediatric hemato-oncologic patients with bacteremia in Seoul National University Children's Hospital, from 2006 to 2010 was conducted. Results : A total of 246 pathogens were isolated, of which 63.4% (n=156) were gram-negative, bacteria 34.6% (n=85) were gram-positive bacteria, and 2.0% (n=5) were fungi. The most common pathogens were Klebsiella spp. (n=61, 24.8%) followed by Escherichia coli (n=31, 12.6%), coagulase-negative staphylococci (n=23, 9.3%), and Staphylococcus aureus (n=22, 8.9 %). Resistance rates of gram-positive bacteria to penicillin, oxacillin, and vancomycin were 85.7%, 65.9%, and 9.5%, respectively. Resistance rates of gram-negative bacteria to cefotaxime, piperacillin/tazobactam, imipenem, gentamicin, and amikacin were 37.2%, 17.1%, 6.2%, 32.2%, and 13.7%, respectively. Overall fatality rate was 12.7%. Gram-negative bacteremia was more often associated with shock (48.4% vs. 11.9%, P <0.01) and had higher fatality rate than gram-positive bacteremia (12.1% vs. 3.0%, P=0.03). Neutropenic patients were more often associated with shock than non-neutropenic patients (39.6 % vs. 22.0%, P =0.04). Conclusion : This study revealed that gram-negative bacteria were still dominant organisms of bloodstream infections in children with hemato-oncologic diseases, and patients with gram-negative bacteremia showed fatal course more frequently than those with gram-positive bacteremia. (Korean J Pediatr Infect Dis 2012;19:131-140)

Purpose : The purpose of this study is to investigate clinical features and causative organisms in febrile infants younger than three months, to help identification of high risk patients for serious bacterial infection (SBI). Methods : A total of 313 febrile infants younger than three months, who had visited Seoul National University Children s ' Hospital from January 2008 to December 2010 were included. Clinical features, laboratory findings, causative organisms, and risk factors of SBI were analyzed by retrospective chart review. Causative bacterial or viral pathogens were identified by gram stain and cultures, rapid antigen tests, or the polymerase chain reaction from clinically reliable sources. Results : Among 313 infants, etiologic organisms were identified in 127 cases (40.6%). Among 39 cases of bacterial infections, Escherichia coli (66.7%) and Streptococcus agalactiae (12.8%) were common. Enterovirus (33.7%), respiratory syncytial virus (19.8%), and rhinovirus (18.8%) were frequently detected in 88 cases of viral infection. Patients with SBI (39 cases) showed significantly higher values of the white blood cell count (14,473 6,824/mm ± 3 vs. 11,254 5,775/mm ± 3 , P =0.002) and the Creactive protein (6.32 8.51 mg/L vs. 1.28 2.35 mg/L, ± ± P <0.001) than those without SBI (274 cases). The clinical risk factors for SBI were the male (OR 3.7, 95% CI 1.5-8.9), the presence of neurologic symptoms (OR 4.8,, and the absence of family members with respiratory symptoms (OR 3.6, 95% CI 1.2-11.3). Conclusion : This study identified common pathogens and risk factors for SBI in febrile infants younger than three months. These findings may be useful to guide management of febrile young infants. (Korean J Pediatr Infect Dis 2012;19:121-130)