Ji Hwan Bang

Kinetics of Serologic Responses to MERS Coronavirus Infection in Humans, South Korea.

We investigated the kinetics of serologic responses to Middle East respiratory syndrome coronavirus (MERS-CoV) infection by using virus neutralization and MERS-CoV S1 IgG ELISA tests. In most patients, robust antibody responses developed by the third week of illness. Delayed antibody responses with the neutralization test were associated with more severe disease.

Bacteremia is a prognostic factor for poor outcome in spontaneous bacterial peritonitis

We performed a retrospective study to determine the influence of bacteremia on the mortality of patients with spontaneous bacterial peritonitis (SBP), a major complication of liver cirrhosis. Patients with SBP with identified pathogens from ascites and/or blood were analyzed by retrospective review of clinical and laboratory records in a university hospital in Korea for 3 y and classified into the bacteremic and non-bacteremic groups. The underlying liver function was determined by model for end-stage liver disease (MELD) score. Microbiological response rate, ascites polymorphonuclear leukocyte (PML) count reduction rate, and SBP-related mortality were compared between the 2 groups. To identify the independent risk factors of mortality, a multiple logistic regression model was used to control for the confounders. A total of 189 patients was enrolled in the study. Among 189 patients, 110 (58.2%) were bacteremic, and 79 (41.8%) non-bacteremic. Escherichia coli was the most common etiologic organism, followed by Klebsiella pneumoniae. MELD scores, microbiological response rate (82.6% vs 88.6%, p=0.295), and ascites PML count reduction rate (33.2% vs 44.8%, p=0.479) were not different between the bacteremic and non-bacteremic group. However, the SBP-related mortality rate of the bacteremic group was significantly higher than that of the non-bacteremic group (37.3% vs 12.7%, p<0.001). Bacteremia (OR =2.86: 95% CI 1.06–7.74, p=0.038), APACHE II score (OR =1.20: 95% CI 1.10–1.31, p<0.001), MELD score (OR =1.07: 95% CI 1.01–1.31, p =0.016) and microbiological no response (OR =5.51: 95% CI 1.82–16.72, p=0.003) were independent risk factors of SBP-related mortality.

Area under the concentration–time curve to minimum inhibitory concentration ratio as a predictor of vancomycin treatment outcome in methicillin-resistant Staphylococcus aureus bacteraemia

There have been few clinical studies on the association between the 24-h area under the concentration-time curve (AUC24) to minimum inhibitory concentration (MIC) ratio and vancomycin treatment outcomes in methicillin-resistant Staphylococcus aureus (MRSA) infections. Patients with MRSA bacteraemia between July 2009 and January 2012 were analysed retrospectively. All adult patients treated with vancomycin for ≥72 h without dialysis were included. The MIC was determined by Etest and broth microdilution (BMD). Initial steady-state AUC24 was estimated using a Bayesian model, and the AUC24/MIC cut-off value for differentiating treatment success and failure was calculated by classification and regression tree (CART) analysis. In total, 76 patients were enrolled; vancomycin treatment failure occurred in 20 patients (26.3%). Catheter-related infection was the most frequent (35.5%), followed by surgical site infection (26.3%), whilst 25 (32.9%) had complicated infections. In univariate analysis, decreased MRSA vancomycin susceptibility (MIC≥1.5 mg/L) and vancomycin trough levels (15-20 mg/L) were not associated with treatment outcomes. In the CART analysis, low initial vancomycin AUC24/MIC (<430 by Etest; <398.5 by BMD) was associated with a higher treatment failure rate (50.0% vs. 25.0%, P=0.039 by Etest; 45.0% vs. 23.2%; P=0.065 by BMD). In multivariate analysis, low initial vancomycin AUC24/MIC was a significant risk factor for treatment failure [adjusted odds ratio (aOR)=4.39, 95% confidence interval (CI), 1.26-15.35 by Etest; aOR=3.73, 95% CI 1.10-12.61 by BMD]. In MRSA bacteraemia, a low initial vancomycin AUC24/MIC is an independent risk factor for vancomycin treatment failure.

Tuberculosis manifested by immune reconstitution inflammatory syndrome during HAART.

The proportion of tuberculosis manifested by immune reconstitution inflammatory syndrome (IRIS) after HAART has not been established. We describe the incidence and clinical features of tuberculosis manifested by IRIS after HAART in an intermediate tuberculosis burden area. The findings suggest that a significant proportion of the tuberculosis occurring early after starting HAART is manifested by IRIS.

Immune reconstitution inflammatory syndrome in the first year after HAART: influence on long-term clinical outcome.

Little is known about the effect of immune reconstitution inflammatory syndrome (IRIS) on the long-term clinical outcome. Of 52 opportunistic infections (OI) occurring within one year after the start of HAART in 387 HIV patients, 33 (63%) were classified as having IRIS. The patients with IRIS showed no significant difference in the AIDS event-free survival curve compared with the matched control group without OI and in contrast to non-IRIS OI.

Viral Load Kinetics of MERS Coronavirus Infection

Middle East respiratory syndrome coronavirus continues to circulate in the Middle East. During a recent outbreak in Korea, changes in MERS coronavirus viral load were determined during the course of illness in 17 patients.

Comparison of serological assays in human Middle East respiratory syndrome (MERS)-coronavirus infection.

Plaque reduction neutralisation tests (PRNT), microneutralisation (MN), Middle East respiratory syndrome (MERS)-spike pseudoparticle neutralisation (ppNT) and MERS S1-enzyme-linked immunosorbent assay (ELISA) antibody titres were compared using 95 sera from 17 patients with MERS, collected two to 46 days after symptom onset. Neutralisation tests correlated well with each other and moderately well with S1 ELISA. Moreover to compare antigenic similarity of genetically diverse MERS-CoV clades, the response of four sera from two patients sampled at two time periods during the course of illness were tested by 90% PRNT. Genetically diverse MERS-CoV clades were antigenically homogenous.

An outbreak of Burkholderia cepacia complex pseudobacteremia associated with intrinsically contaminated commercial 0.5% chlorhexidine solution

BACKGROUND Burkholderia cepacia complex (Bcc) is well-known for intrinsic resistance to certain antiseptics. We experienced a sudden rise in Bcc bloodstream infections in a 786-bed hospital. An investigation was conducted to identify the source and to intervene in the ongoing infections. METHODS The cases were defined as patients with positive blood cultures for Bcc from October 10, 2013-December 16, 2013. We reviewed medical records, interviewed health care workers, and audited the clinical laboratory. A microbiologic culture for a suspected antiseptic was performed, and interventions were instituted. RESULTS During the outbreak period, Bcc were isolated from 46 blood cultures from 40 patients. The temporal and spatial distributions did not reveal common factors. The clinical features of the case patients suggested pseudobacteremia. A 0.5% chlorhexidine solution product was found to be contaminated with Bcc and had been misused as a skin antiseptic during blood culture. After withdrawal of the product and staff education, the outbreak was terminated. CONCLUSION The pseudobacteremia was caused by contaminated 0.5% chlorhexidine from a single company. This contamination was permitted by multiple breaches of infection control principles that could have caused significant outbreaks of true infections. Regulatory actions at the government level are needed to ensure the sterility of antiseptics.

Urbanization of scrub typhus disease in South Korea.

Background Scrub typhus is an endemic disease in Asia. It has been a rural disease, but indigenous urban cases have been observed in Seoul, South Korea. Urban scrub typhus may have a significant impact because of the large population. Methods Indigenous urban scrub typhus was epidemiologically identified in Seoul, the largest metropolitan city in South Korea, using national notifiable disease data from 2010 to 2013. For detailed analysis of clinical features, patients from one hospital that reported the majority of cases were selected and compared to a historic control group. Chigger mites were prospectively collected in the city using a direct chigger mite-collecting trap, and identified using both phenotypic and 18S rDNA sequencing analyses. Their infection with Orientia tsutsugamushi was confirmed by sequencing the 56-kDa antigen gene. Results Eighty-eight cases of urban scrub typhus were determined in Seoul. The possible sites of infection were mountainous areas (56.8%), city parks (20.5%), the vicinity of one’s own residence (17.0%), and riversides (5.7%). Eighty-seven chigger mites were collected in Gwanak mountain, one of the suspected infection sites in southern Seoul, and seventy-six (87.4%) of them were identified as Helenicula miyagawai and eight (9.2%) as Leptotrombidium scutellare. Pooled DNA extracted from H. miyagawai mites yielded O. tsutsugamushi Boryong strain. Twenty-six patients from one hospital showed low APACHE II score (3.4 ± 2.7), low complication rate (3.8%), and no hypokalemia. Conclusions We identified the presence of indigenous urban scrub typhus in Seoul, and a subgroup of them had mild clinical features. The chigger mite H. miyagawai infected with O. tsutsugamushi within the city was found. In endemic area, urban scrub typhus needs to be considered as one of the differential febrile diseases and a target for prevention.

Prevalence of primary antiretroviral resistance: trends in Korea.

Primary drug resistance is an emerging problem in HIV infections. We have investigated the current prevalence of primary resistance in Korea and compared it with previous data. Drug-naive HIV patients attending the outpatient clinic of Seoul National University Hospital between April and August 2006 were enrolled. A medical interview and a genotypic resistance test were performed for each patient. The International AIDS Society-USA Panel consensus statement issued in 2006 was used to define resistance mutations. Eighty-one drug-naive HIV patients were enrolled. Two (2.5%) were infected with primary drug-resistant virus: M41L and K103N, respectively. In our previous study, conducted between 1998 and 2002, three (6%) of 50 subjects harbored resistant viruses. Thus the frequency of primary resistance was lower in the present sample than in the earlier one, though the difference is not statistically significant (p = 0.37). In view of our findings, routine antiretroviral resistance tests for drug-naive HIV patients are not obligatory in Korea.