Dong Hee Whang

Wide dissemination of OXA-type carbapenemases in clinical Acinetobacter spp. isolates from South Korea

Carbapenem-resistant Acinetobacter spp. are being increasingly reported worldwide, including in South Korea, where we examined 144 representative isolates collected in a nationwide hospital survey in 2005. Metallo-beta-lactamases were detected in only 19.4% of isolates, none of which were Acinetobacter baumannii, whereas 74.3% of isolates (mostly A. baumannii) expressed bla(OXA) carbapenemase genes. Among the latter, 47 had bla(OXA-23)-like genes and 56 had upregulated bla(OXA-51)-like variants, including bla(OXA-66), (-83), (-109) and (-115); bla(OXA-115) was a novel variant, detected in two isolates. bla(OXA-72) (bla(OXA-40)-like) was detected in only a single Acinetobacter baylyi isolate, whilst three Acinetobacter calcoaceticus isolates had both bla(VIM-2)-like and bla(OXA-58) genes. Pulsed-field gel electrophoresis (PFGE) suggested the spread of A. baumannii clones with OXA carbapenemases within and between hospitals. In conclusion, the recent increase in imipenem-resistant Acinetobacter spp. from South Korea is mostly due to OXA-type carbapenemases.

Evaluation of the accuracy of serum human epididymis protein 4 in combination with CA125 for detecting ovarian cancer: a prospective case-control study in a Korean population.

Abstract Background: This study aimed to determine the serum concentrations of CA125 and human epididymis protein 4 (HE4) in patients with ovarian cancer, and to evaluate the sensitivity and specificity of these biomarkers for differentiating between patients with benign gynecological disease and those with ovarian cancer, when used alone and in combination in a Korean population. Methods: We consecutively recruited 159 women with an adnexal mass, including 78 women with ovarian cancer. A total of 224 healthy women served as controls. The serum concentrations of HE4 and CA125 were analyzed using immunochemiluminescence assays. The concentrations of the markers were compared among the different subgroups, and the diagnostic accuracy of each marker and the combination of the two markers was assessed by plotting receiver operating characteristic (ROC) curves. In addition, the Risk of Ovarian Malignancy Algorithm (ROMA) was utilized to categorize patients into low- and high-risk groups for epithelial ovarian cancer. Results: Serum HE4 and CA125 concentrations were significantly higher in the ovarian cancer patients compared with those seen in patients with benign disease or in the healthy controls (p<0.0001 in both). In patients with an adnexal mass, the area under the ROC curve was higher when the combination of the markers was used compared with use of CA125 only. Using ROMA, patients could be successfully classified into high- and low-risk group, with 87.5% sensitivity at a specificity of 93.8%. Conclusions: These findings suggest that measuring serum HE4 concentrations along with CA125 concentrations may provide higher accuracy for detecting ovarian cancer.

Multicentre study of the prevalence of toxigenic Clostridium difficile in Korea: results of a retrospective study 2000-2005.

The prevalence of toxigenic Clostridium difficile in Korea has been reported to be approximately 60-80%. Although the prevalence of the tcdA(-)tcdB(+) C. difficile strain was less then 5% prior to the year 2000, it has become an emerging nosocomial pathogen in Korea. Therefore, we have attempted to determine the multicentre nationwide prevalence of tcdA(+)tcdB(+) and tcdA(-)tcdB(+) C. difficile for epidemiological purposes. C. difficile strains (n=724, 30 from 2000, 80 from 2001, 74 from 2002, 76 from 2003, 179 from 2004, 285 from 2005) were obtained retrospectively from January 2000 to December 2005 from in-patients at 6 hospitals, all of whom were suspected of having C. difficile-associated disease (CDAD), colitis or pseudomembranous colitis. The numbers of participating hospitals varied yearly (1 in 2000, 2 in 2001-2003, 3 in 2004, 5 in 2005). The hospitals were located in Seoul (n=4), Kyunggi Province (n=1) and Busan (n=1), Korea. PCR assays for tcdA and tcdB genes were conducted using 724 unduplicated C. difficile isolates. The mean prevalence of tcdA(+)tcdB(+) and tcdA(-)tcdB(+) C. difficile strains over the 6 years was 51.8 % (38.4-59.3%) and 25.8%(10-56.0%), respectively. The mean prevalence of tcdA(-)tcdB(+) C. difficile strains was less than 7% until 2002, but began to increase in 2003 (13.2%) and achieved a peak in 2004 (50.3%). In 2005, the mean prevalence of tcdA(+)tcdB(+) and tcdA(-)tcdB(+) C. difficile strains was 47.7% (30.9-60.3%) and 27.0% (17.6-54.8%), respectively. This nationwide epidemiological study showed that tcdA(-)tcdB(+) C. difficile strains have already spread extensively throughout Korea, and our results provide basic data regarding the controversies currently surrounding the toxigenicity of tcdA(-)tcdB(+) C. difficile. The use of enzyme immunoassays capable of detecting both TcdA and TcdB is strongly recommended for the diagnosis of CDAD in microbiology laboratories, in order to control the spread of the tcdA(-)tcdB(+) strains of C. difficile.

Prevalence of antibodies to hepatitis B core antigen and occult hepatitis B virus infections in Korean blood donors

BACKGROUND: This study was performed to determine the prevalence of antibodies to hepatitis B core antigen (anti‐HBc) among Korean blood donors and frequencies of hepatitis B virus (HBV) DNA and antibodies to hepatitis B surface antigen (anti‐HBs) in anti‐HBc–positive donors.

Trichuris trichiura Infection Diagnosed by Colonoscopy: Case Reports and Review of Literature

Trichuris trichiura, commonly referred to as a whipworm, has a worldwide distribution, particularly among countries with warm, humid climates. In Korea, trichuriasis was a highly prevalent soil-transmitted helminthiasis until the 1970s. However, the nationwide prevalence decreased to 0.02% in 2004 as a result of national control activities and improvement in the socioeconomic status of Koreans. Most infected individuals have no distinct symptoms, if lightly infected. The diagnosis is typically confirmed by detection of T. trichiura eggs on examination of a stool sample; few reports have described detection of the parasite during colonoscopy. Recently, we managed 4 patients with trichuriasis who were diagnosed by detection of the parasite on colonoscopy, and we reviewed the literature on the colonoscopic diagnosis of T. trichiura in Korea. We suggest that colonoscopy might be a useful diagnostic tool, especially when infected by only a few male worms with no eggs in the stool.

Occult hepatitis B virus infection and blood transfusion

Transfusion-transmitted infections including hepatitis B virus (HBV) have been a major concern in transfusion medicine. Implementation of HBV nucleic acid testing (NAT) has revealed occult HBV infection (OBI) in blood donors. In the mid-1980s, hepatitis B core antibody (HBc) testing was introduced to screen blood donors in HBV non-endemic countries to prevent transmission of non-A and non-B hepatitis. That test remains in use for preventing of potential transmission of HBV from hepatitis B surface antigen (HBsAg)-negative blood donors, even though anti-hepatitis C virus tests have been introduced. Studies of anti-HBc-positive donors have revealed an HBV DNA positivity rate of 0%-15%. As of 2012, 30 countries have implemented HBV NAT. The prevalence of OBI in blood donors was estimated to be 8.55 per 1 million donations, according to a 2008 international survey. OBI is transmissible by blood transfusion. The clinical outcome of occult HBV transmission primarily depends on recipient immune status and the number of HBV DNA copies present in the blood products. The presence of donor anti-HBs reduces the risk of HBV infection by approximately five-fold. The risk of HBV transmission may be lower in endemic areas than in non-endemic areas, because most recipients have already been exposed to HBV. Blood safety for HBV, including OBI, has substantially improved, but the possibility for OBI transmission remains.

Antimicrobial Susceptibility of Stenotrophomonas maltophilia Isolates from Korea, and the Activity of Antimicrobial Combinations against the Isolates

The aim of this study was to determine antimicrobial susceptibility of recent clinical Stenotrophomonas maltophilia isolates from Korea, and to compare the activity levels of several combinations of antimicrobials. A total of 206 non-duplicate clinical isolates of S. maltophilia was collected in 2010 from 11 university hospitals. Antimicrobial susceptibility testing was performed using the Clinical Laboratory Standards Institute agar dilution method. In vitro activity of antimicrobial combinations was tested using the checkerboard method. The susceptibility rates to trimethoprim-sulfamethoxazole and minocycline were 96% and 99%, respectively. The susceptibility rate to levofloxacin was 64%. All of four antimicrobial combinations showed synergy against many S. maltophilia isolates. A combination of trimethoprim-sulfamethoxazole plus ticarcillin-clavulanate was most synergistic among the combinations. None of the combinations showed antagonistic activity. Therefore, some of the combinations may be more useful than individual drugs in the treatment of S. maltophilia infection. Further clinical studies are warranted to validate our in vitro test results.

A Case of Leclercia adecarboxylata Endocarditis in a Woman With Endometrial Cancer

Leclercia adecarboxylata, a motile, gram-negative bacillus of the enterobacteriaceae family, is rarely recovered as a pathogen. We report an exceptionally rare case of L. adecarboxylata endocarditis complicated by embolization of the kidney and spleen in a 48-year-old woman with endometrial cancer. After 4 weeks of antimicrobial treatment, she recovered without sequelae.

Allele and Haplotype Frequencies of Human Leukocyte Antigen-A, -B, and -DR Loci in Koreans: DNA Typing of 1,500 Cord Blood Units

BACKGROUND The HLA system is known to be the most polymorphic genetic system in human, and HLA allele and haplotype distribution varies widely among different ethnic groups. This study was performed to examine the frequencies of HLA alleles and haplotypes in Koreans. METHODS We examined HLA-A, -B, and -DR alleles at the serologic level in 1,500 cord blood units obtained from Koreans using the PCR-sequence specific oligonucleotide (SSO) method. Allele and haplotype frequencies were estimated by the maximum likelihood method using the computer program developed for the 11th International Histocompatibility Workshop. RESULTS HLA alleles found in Koreans were 12 in A, 31 in B, and 13 in DR loci. Most frequent alleles with frequencies > or =10% in each locus in decreasing order of frequency were: A2, A24, A33, A11; B62; DR4, DR15, DR9, and DR13. Two-locus haplotypes with frequencies > or =0.1% were 104 A-B and 115 B-DR haplotypes, among which those with frequencies > or =1.0% showing significant positive linkage disequilibrium (P< or =0.001) were 21 A-B and 20 B-DR haplotypes. A total of 169 A-B-DR haplotypes with frequencies > or =0.1% were identified. The results were similar to those of a previous study in 1,600 Koreans, although some differences were noted in the distribution of some less frequent alleles or haplotypes with frequencies < or =0.5%. CONCLUSIONS We provided the allele and haplotype frequencies of HLA-A, -B, and -DR in cord blood units of Korean ethnicity defined by a DNA typing method, which can be used as basic data on Koreans for organ transplantation and disease association studies.

Reference interval and determinants of the serum homocysteine level in a Korean population

In this study, we estimated the reference intervals of the serum homocysteine (Hcy) level using two automated immunoassays, and we demonstrated the effects of various factors on the Hcy level in a Korean population. We calculated the gender‐ and assay‐specific reference intervals using the data from 809 healthy Koreans, and we assessed the effects of physiologic and lifestyle factors on the Hcy level. The upper limit was higher in males (19.21 and 19.76 μmol/l) than that in females (14.99 μmol/l and 15.16 μmol/l, AxSym and ADVIA centaur, respectively); the upper limits were comparable between the two assays. Smokers, vitamin nonusers, and persons without regular exercise showed a lower folate level and a higher Hcy level. The risk of hyperhomocysteinemia was significantly associated with the male gender (adjusted OR: 5.705, P‐value: 0.008) and with the low folate level group (adjusted OR: 10.412, P‐value: 0.002) on the multivariate analysis. The Hcy level was significantly different according to various factors, especially in the gender and folate level. The reference interval should be determined for each ethnic population and for each assay. The appropriate cutoff for assessing the risk for cardiovascular disease or stroke should also be validated in each population. J. Clin. Lab. Anal. 25:317–323, 2011.