To survey healthcare-associated Clostridium difficile infection (HA-CDI) in a 900-bed tertiary-care hospital, we prospectively investigated the epidemiology of CDI and distribution of PCR-ribotypes. From February 2009 through January 2010, all patients with HA-CDI were enrolled. Epidemiological information and prescription records for antibiotics were collected. The C. difficile isolates were characterized using reference strains and were tested for antibiotic susceptibility. During the survey, incidence of HA-CDI was 71.6 per 100 000 patient-days. In total, 140 C. difficile isolates were obtained from 166 patients with HA-CDI. The PCR-ribotyping yielded 38 distinct ribotypes. The three most frequently found ribotypes made up 56.4% of all isolates; they comprised 37 isolates (26.4%) of PCR-ribotype 018, 22 (15.7%) of toxin A-negative PCR-ribotype 017, and 20 (14.3%) of PCR-ribotype 001. Clostridium difficile PCR-ribotype 018 was present in all departments throughout the hospital during the 11 months, whereas ribotype 017 and ribotype 001 appeared mostly in the pulmonary department. Hypervirulent C. difficile PCR-ribotype 027 was detected in 1 month on two wards. The incidence of CDI in each department showed a seven-fold difference, which correlated significantly with the amount of prescribed clindamycin (R = 0.783, p 0.013) or moxifloxacin (R = 0.733, p 0.025) in the departments. The rates of resistance of the three commonest ribotypes to clindamycin and moxifloxacin were significantly higher than those of other strains (92.1% versus 38.2% and 89.5% versus 27.3%, respectively). CDI is an important nosocomially acquired infection and this study emphasizes the importance of implementing country-wide surveillance to detect and control CDI in Korea.

Presellar extension of the bone window combined with removal of the sellar floor results in the transsphenoidal supradiaphragmatic intradural approach. One tuberculum sella meningioma and another suprasellar Rathke's cleft cyst confined to the pituitary stalk were removed via this approach. The presellar extension of the bone window was performed with the sublabial transseptal transsphenoidal technique. Furthermore, the dissection of the anterior intercavernous sinus, diaphragma sella, and arachnoid trabecula has allowed a wide surgical field of pre- and suprasellar areas and facilitates safe removal of lesions without significant surgical complications in selected cases.

The purpose of this study was to identify factors associated with relapses or re-infections in patients with recurring Clostridium difficile infections (CDIs). From September 2008 to January 2012, cases with two or more isolates from consecutive CDI episodes were included. PCR-ribotyping and multilocus variable-number tandem-repeat analysis were performed using paired isolates. Among 473 patients, 68 (14.4%) experienced one to five recurrences. Fifty-one of these with two or more isolates from consecutive CDI episodes were included in the study; 25 (49%) were classified as relapses and 26 (51%) as re-infections. Recurrence interval was shorter in the relapse group (26.0 versus 67.5 p 0.001), but more patients in the re-infection group were hospitalized during recurrence interval (53.8% versus 8.0%, p<0.001). Relapse rates in infections by ribotype 017, ribotype 018 and other ribotypes were 63.6%, 63.6% and 22.2%, respectively (p 0.274, p 0.069, and p 0.005). In multivariate logistic regression, infections by ribotypes 017 and 018 were associated with CDI relapse (OR 4.77, 95% CI 1.02-22.31, p 0.047; OR 11.49, 95% CI 2.07-63.72, p 0.005). Conversely, admission during recurrence interval lowered the risk of relapse (OR 0.044, 95% CI 0.006-0.344, p 0.003). In conclusion, relapse was more likely when infection was caused by PCR ribotypes 017 and 018.

To model hydraulic fracture propagation in naturally fractured reservoirs, fracture propagation is generally assumed to be a single planar fracture propagated only in the vertical direction from a horizontal well, regardless of the presence of natural fractures. In this paper, we developed a multi-stage hydraulic fracture propagation model using a twisted multiple planar fracture that is able to describe the propagation of hydraulic fractures more realistically. In propagating hydraulic fractures, we used two criteria: maximum tangential stress, to determine the fracture initiation angle, and whether a hydraulic fracture passes through a natural fracture. The developed model was used with a commercial reservoir simulator through grid mapping in the form of a discrete fracture network using microseismic data. The results of the verification matched the experimental results well for various intersection angles and maximum horizontal stress directions. In the investigation of the direction of maximum horizontal stress, the frictional coefficient of the fracture interface, and fracture orientation, hydraulic fracture propagation modeling results showed that the hydraulic fracture passed through a natural fracture, and thereafter propagated in a manner suitably consistent with the theoretical results, based on a fracture interaction criterion. After confirming the twisted multiple planar fracture model suggested in this work, discrepancies were found in the fracture connectivity and the stimulated reservoir volume. This indicates that the twisted multiple planar fracture approach, which is more realistic in terms of fracture propagation, is extremely important in evaluating the initial gas in place, calculated according to the stimulated reservoir volume.

When analyzing production data during reservoir characterization, pressure transient analysis requires a constant production rate during the entire production period. However, because of the extremely low permeability of shale formations, the flow regime changes over the long period of production. Therefore, it is rarely possible to acquire production data at a constant rate. In addition, as pressure declines with production in a shale gas reservoir, desorption of gas occurs, leading to nonlinearities due to large changes in gas compressibility, and it should be linearized for the use of deconvolution. In this study, we suggest sorption correction for pseudopressure using material balance equation to linearize the pseudopressure–rate relationship. By using this sorption correction term for pseudopressure in the deconvolution, we carried out pressure transient analysis with production data from a shale gas well to obtain the reservoir characteristics. The results show that, without sorption correction, the pseudopressure decline and its derivative varied depending on the magnitude of the desorption. However, with the correction applied, the curves were almost identical regardless of desorption. In the results of the deconvolution analysis with and without the sorption correction, pseudo-linear and pseudo-pseudosteady state flow periods appeared at different times, which explains the anomalous results in the pressure transient analysis. By implementing those results, we analyzed production data acquired from Fayetteville shale. The results show that the reservoir permeability, stimulated reservoir volume, and fracture half-length depended on the use of sorption correction for pseudopressure.