Hee Bong Shin

Investigation of Toxin Gene Diversity, Molecular Epidemiology, and Antimicrobial Resistance of Clostridium difficile Isolated from 12 Hospitals in South Korea

BACKGROUND Clostridium difficile is a major cause of antibiotic-associated diarrhea. The objective of this study was to characterize clinical isolates of C. difficile obtained from various regions in Korea with regard to their toxin status, molecular type, and antimicrobial susceptibility. METHODS We analyzed a total of 408 C. difficile isolates obtained between 2006 and 2008 from 408 patients with diarrhea in 12 South Korean teaching hospitals. C. difficile toxin genes tcdA, tcdB, cdtA, and cdtB were detected by PCR. Molecular genotyping was performed by PCR ribotyping. Antimicrobial susceptibilities of the 120 C. difficile isolates were assessed by agar dilution methods. RESULTS Among 337 toxigenic isolates, 105 were toxin A-negative and toxin B-positive (A(-)B(+)) and 29 were binary toxin-producing strains. PCR ribotyping showed 50 different ribotype patterns. The 5 most frequently occurring ribotypes comprised 62.0% of all identified ribotypes. No isolate was susceptible to cefoxitin, and all except 1 were susceptible to piperacillin and piperacillin-tazobactam. The resistance rates of isolates to imipenem, cefotetan, moxifloxacin, ampicillin, and clindamycin were 25%, 34%, 42%, 51%, and 60%, respectively. The isolates showed no resistance to metronidazole or vancomycin. CONCLUSIONS This is the first nationwide study on the toxin status, including PCR ribotyping and antimicrobial resistance, of C. difficile isolates in Korea. The prevalence of A-B+ strains was 25.7%, much higher than that reported from other countries. Binary toxin-producing strains accounted for 7.1% of all strains, which was not rare in Korea. The most prevalent ribotype was ribotype 017, and all A-B+ strains showed this pattern. We did not isolate strains with decreased susceptibility to metronidazole or vancomycin.

Increase in the Prevalence of Carbapenem-Resistant Acinetobacter Isolates and Ampicillin-Resistant Non-Typhoidal Salmonella Species in Korea: A KONSAR Study Conducted in 2011.

Background Antimicrobial surveillance is important for providing an up-to-date understanding of the epidemiology of antimicrobial resistance and for creating a forum for rational drug development. In this study, we analyzed antimicrobial test data generated in 2011 by hospitals and commercial laboratories participating in the Korean Nationwide Surveillance of Antimicrobial Resistance program (KONSAR). Materials and Methods Data on the results of susceptibility tests conducted in 32 hospitals and two commercial laboratories were analyzed. Data on isolates from patients admitted to an intensive care unit (ICU) and those admitted to other wards were compared. Intermediate susceptibility was not analyzed and duplicate isolates were excluded. Results Escherichia coli was the most prevalent organism identified in both the hospital and commercial laboratories. Among the hospital isolates, methicillin-resistant Staphylococcus aureus (MRSA), penicillin G-non-susceptible Streptococcus pneumoniae, and ampicillin-resistant Enterococcus faecium remained as prevalent as they were in 2009. The proportion of vancomycin-resistant E. faecium (VR-EFM) slightly decreased from 29% in 2009 to 23% in 2011. Resistance rates of Klebsiella pneumoniae to ceftazidime, cefoxitin, fluoroquinolone, and amikacin were 24%, 14%, 27%, and 8%, respectively. Resistance rates of Pseudomonas aeruginosa to fluoroquinolone, ceftazidime, imipenem, and amikacin were 33%, 20%, 22%, and 16%, respectively, whereas those of Acinetobacter spp. resistance were 71%, 66%, 64, and 51%, respectively. The prevalence of oxyimino-cephalosporin-resistant E. coli and K. pneumoniae, carbapenem-resistant Acinetobacter spp. and P. aeruginosa, MRSA, and VR-EFM among ICU isolates was higher than those among non-ICU isolates. Extended-spectrum β-lactamase-producing E. coli and K. pneumoniae, imipenem-resistant P. aeruginosa, and VR-EFM were more prevalent among isolates from commercial laboratories than those from hospitals. Resistance rates of K. pneumoniae to ceftazidime and amikacin decreased from 32% and 24% in 2005 to 24% and 8% in 2011, respectively. The resistance rate of P. aeruginosa to amikacin decreased from 22% in 2005 to 16% in 2011. The proportion of imipenem-resistant Acinetobacter spp. increased from 16% in 2005 to 64% in 2011. Conclusions The prevalence of MRSA, penicillin G-non-susceptible S. pneumoniae, and ampicillin-resistant E. faecium among clinical isolates tested in laboratories remained high. Multidrug resistance was more prevalent among isolates from ICUs. The prevalence of ceftazidime-resistant and amikacin-resistant K. pneumoniae and amikacin-resistant P. aeruginosa decreased after 2005, while the prevalence of imipenem-resistant Acinetobacter spp. increased.

Vancomycin-Tolerant Streptococcus pneumoniae in Korea

ABSTRACT A nationwide surveillance study was undertaken to monitor antimicrobial resistance among clinical isolates of Streptococcus pneumoniae in Korea, with a special focus on vancomycin tolerance. For the 6-month period from March to August 2002, clinical isolates of S. pneumoniae were collected from 11 university hospitals and 1 reference laboratory. One-hundred eighty-eight isolates were measured for lysis rates after exposure to vancomycin for 4 h. Two vancomycin-tolerant S. pneumoniae (VTSP) strains, S3 and H8, were isolated from sputum cultures of two patients, who had stayed in intensive-care units of different hospitals with long-term antibiotic therapy and were not treated for pneumococcal pneumonia. The penicillin, cefotaxime, and vancomycin MICs for S3 were 8 μg/ml, >16 μg/ml, and 0.5 μg/ml, and those for H8 were 2 μg/ml, 2 μg/ml, and 0.5 μg/ml, respectively. While S3 belonged to serotype 23F and was autolysin defective, H8 belonged to serotype 13F and had intact autolysin. These strains were not clonally related as determined by pulsed-field gel electrophoresis of chromosomal DNA. In agreement with previous reports, both isolates showed pairing of TIGR4 vex2 with R6 pep27 and had two identical amino acid substitutions, Q441K in vncS and N25D in vex2. These findings indicate that two VTSP strains have emerged independently in Korea, suggesting a prevalence rate of 1.1%. The emergence of VTSP would be a serious threat in Korea, where there are significant rates of penicillin resistance in S. pneumoniae. Monitoring of the prevalence of VTSP and further investigation of the clinical relevance of VTSP are warranted.

Evaluation of Peptide Nucleic Acid Probe-based Real-time PCR for Detection of Mycobacterium tuberculosis Complex and Nontuberculous Mycobacteria in Respiratory Specimens

Background A peptide nucleic acid (PNA) probe-based real-time PCR (PNAqPCR™ TB/NTM detection kit; PANAGENE, Korea) assay has been recently developed for the simultaneous detection of Mycobacterium tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM) in clinical specimens. The study was aimed at evaluation of the performance of PNA probe-based real-time PCR in respiratory specimens. Methods To evaluate potential cross-reactivity, the extracted DNA specimens from Mycobacterium species and non-mycobacterial species were tested using PNA probe-based real-time PCR assay. A total of 531 respiratory specimens (482 sputum specimens and 49 bronchoalveolar washing fluid specimens) were collected from 230 patients in July and August, 2011. All specimens were analyzed for the detection of mycobacteria by direct smear examination, mycobacterial culture, and PNA probe-based real-time PCR assay. Results In cross-reactivity tests, no false-positive or false-negative results were evident. When the culture method was used as the gold standard test for comparison, PNA probe-based real-time PCR assay for detection of MTBC had a sensitivity and specificity of 96.7% (58/60) and 99.6% (469/471), respectively. Assuming the combination of culture and clinical diagnosis as the standard, the sensitivity and specificity of the new real-time PCR assay for detection of MTBC were 90.6% (58/64) and 99.6% (465/467), respectively. The new real-time PCR for the detection of NTM had a sensitivity and specificity of 69.0% (29/42) and 100% (489/489), respectively. Conclusions The new real-time PCR assay may be useful for the detection of MTBC in respiratory specimens and for discrimination of NTM from MTBC.

Identification of a novel mutation in the PTCH gene in a Korean family with naevoid basal cell carcinoma syndrome

accumulation (and hence fluorescence), the skin type of our patient (type I) may have increased the severity of the reaction observed. Guidelines for the use of topical PDT have been recommended by the British Photodermatology Group. These guidelines do not specifically advise the use of a test exposure to PDT, although many practitioners would reasonably advocate treatment of a small area prior to large-field exposure. In our case, it was felt that the mild to moderate reactions seen after treatments of the sBCC on the shoulder were a sufficient indicator that treatment of the larger field could be performed safely, although with hindsight this was not the case. This report highlights that clinicians should exercise caution and that a test exposure to ALA-PDT may be needed when considering treatment to large areas, patients with skin type I ⁄ II, and those with extensive actinic damage, and ⁄ or with strong ALA-induced fluorescence. Indeed, we have changed our own clinical practice as a result of this case, and we now only treat truncal areas up to 50 mm in diameter at first treatment, and a maximum of a 100-mm diameter field subsequently.

The Association between Intraocular Pressure and Predictors of Coronary Heart Disease Risk in Koreans

Elevated intraocular pressure (IOP) is one of the major risk factors for glaucomatous visual field defects. Each individual systemic risk factor of coronary heart disease (CHD) is associated with elevated IOP, although no reports have argued for a correlation between the risk factors for CHD and IOP after a comprehensive or collective analysis. The National Cholesterol Education Program Adult Treatment Panel III presented the Framingham projection, which can predict the risk of CHD quantitatively. We investigated the association between IOP and the Framingham projection in 16,383 Korean subjects. The Framingham projection was applied using the indicated risk factors. The associations between the Framingham projection and IOP and the influences of the risk factors on the IOP were examined. The Framingham projection was correlated with the mean IOP in women (p<0.05). The relationship between IOP and systemic variables other than smoking was significant (p<0.05). The mean IOP was significantly higher in the high-risk CHD group than in the low-risk group based on the Framingham projection (p<0.05). Because an elevated IOP was associated with cardiovascular risk factors, subjects with a high CHD risk based on the Framingham projection need continuous monitoring for IOP to prevent glaucomatous visual field defects.

Comparison of MALDI-TOF MS, Housekeeping Gene Sequencing, and 16S rRNA Gene Sequencing for Identification of Aeromonas Clinical Isolates

Purpose The genus Aeromonas is a pathogen that is well known to cause severe clinical illnesses, ranging from gastroenteritis to sepsis. Accurate identification of A. hydrophila, A. caviae, and A. veronii is important for the care of patients. However, species identification remains difficult using conventional methods. The aim of this study was to compare the accuracy of different methods of identifying Aeromonas at the species level: a biochemical method, matrix-assisted laser desorption ionization mass spectrometry-time of flight (MALDI-TOF MS), 16S rRNA sequencing, and housekeeping gene sequencing (gyrB, rpoB). Materials and Methods We analyzed 65 Aeromonas isolates recovered from patients at a university hospital in Korea between 1996 and 2012. The isolates were recovered from frozen states and tested using the following four methods: a conventional biochemical method, 16S rRNA sequencing, housekeeping gene sequencing with phylogenetic analysis, and MALDI-TOF MS. Results The conventional biochemical method and 16S rRNA sequencing identified Aeromonas at the genus level very accurately, although species level identification was unsatisfactory. MALDI-TOF MS system correctly identified 60 (92.3%) isolates at the species level and an additional four (6.2%) at the genus level. Overall, housekeeping gene sequencing with phylogenetic analysis was found to be the most accurate in identifying Aeromonas at the species level. Conclusion The most accurate method of identification of Aeromonas to species level is by housekeeping gene sequencing, although high cost and technical difficulty hinder its usage in clinical settings. An easy-to-use identification method is needed for clinical laboratories, for which MALDI-TOF MS could be a strong candidate.

A novel cis-AB variant allele arising from a de novo nucleotide substitution c.796A>G (p.M266V) in the B glycosyltransferase gene.

Cis‐AB, a rare ABO variant, is the result of a mutated ABO gene that produces a glycosyltransferase enzyme with dual A and B glycosyltransferase activity. It may lead to ABO discrepancies and a delay in establishing the blood group. To date, there have been no reports of a de novo mutation leading to a cis‐AB allele.

Clinical Characteristics and ALB Gene Mutation Analysis of Korean Patients with Bisalbuminemia

BACKGROUND Bisalbuminemia is a hereditary or an acquired condition characterized by the presence of 2 albumin variants with different mobilities on serum protein electrophoresis (SPE). The clinical significance of bisalbuminemia has not been clearly established. However, some regions of the albumin variant may affect the biochemical analysis of biomolecules such as steroid or thyroid hormones by altering their albumin-binding affinities. In this study, we analyzed the clinical manifestations, genetic variations, and the albumin-binding characteristics in Korean patients with bisalbuminemia. METHODS We performed SPE for samples from 580 Korean subjects and identified bisalbuminemia on the basis of the results of SPE. The clinical and biochemical characteristics, ALB gene mutations, and the structures of the albumin variants of patients with bisalbuminemia were analyzed. RESULTS SPE showed bisalbuminemia in 2 patients. One patient showed a genetic variation known as Nagasaki-1 (Asp293Gly) and the other showed a hitherto unreported missense mutation (c.593A>T; Lys198Ile). In both cases, the serum concentrations of the substances with binding affinity for albumin were not affected, and the mutation sites of the albumin were not located with the protein-binding loci. CONCLUSIONS The 2 Korean patients with bisalbuminemia showed genetic variations, including a novel missense mutation. The ALB gene analysis with 3D modeling is useful for determining the nature of bisalbuminemia and for predicting the effects on the albumin-binding affinity of other biochemical compounds.

A Case of Chronic Myeloid Leukemia With Rare Variant ETV6/ABL1 Rearrangement

Dear Editor, The translocation (9;12)(q34;p13) ETV6/ABL1 rearrangement is a rare but recurrent chromosomal translocation associated with a variety of hematological malignancies, including CML, atypical CML, AML, and ALL [1]. The structure of the ETV6/ABL1 oncoprotein is similar to that of BCR/ABL1, and they initiate similar downstream pathways [2]. There are two ETV6/ABL1 fusion isoforms: the type A isoform, which fuses ETV6 exon 4 with ABL1 exon 2; and the type B isoform, which fuses ETV6 exon 5 with ABL1 exon 2 [3, 4]. To date, 30 cases of ETV6/ABL1 fusion have been reported [5, 6], and only one of these cases resulted in CML with positive BCR/ABL1 rearrangement [7]. Herein, we report a rare case of CML with ETV6/ABL1 rearrangement. A 54-yr-old male was admitted with persistent leukocytosis. Complete blood counts showed a white blood cell count of 21.7 ×10/L with 1% blasts, Hb of 126 g/L, and platelet count of 294 ×10/L. Physical examination was unremarkable. Bone marrow (BM) analysis showed typical characteristics of CML (Fig. 1A, B). Chromosomal analysis of the BM cells demonstrated a balanced t(9;12)(q34;p13) translocation, which was not the Philadelphia chromosome (Fig. 1C). FISH analysis with probes for BCR/ABL1 (Abbott Vysis, Des Plaines, IL, USA detected no fusion signal. However, reverse transcriptase (RT)-PCR analysis of the BCR/ ABL1 fusion transcripts yielded positive results; the reaction product was 700 bp long, indicating positive rearrangement and hence, presence of the P230 chimeric protein at the molecular level (Fig. 1D). To visualize the ETV6/ABL1 fusion signal, we prepared a mixture of two commercially available, locus-specific identifiers: a BCR/ABL1 dual color, dual fusion translocation probe, and an ETV6/RUNX1 extra signal dual color translocation probe (Abbott Vysis) (Fig. 1E, F). Metaphase and interphase FISH with the mixed BCR/ABL1 and ETV6/RUNX1 probes showed one yellow fusion signal at 9q34, which was derived from a green signal from ETV6 and a red signal from ABL1 (Fig. 1G, H). RT-PCR analysis of the ETV6/ABL1 fusion transcript was positive for the 1,141-bp product, indicating a type B fusion (Fig. 1D). After diagnosis, the patient was transferred to another hospital, and therefore, follow-up BM examination was not possible. ETV6/ABL1 rearrangement has been reported to result in enhanced tyrosine kinase activity and neoplastic transformation [3, 8]. A total of 13 cases of ETV6/ABL1-positive or atypical CML have been reported to date (Table 1) [5, 7]. Among those cases, including the present case, two were BCR/ABL1 fusion-positive and 11 were either unknown or negative for the BCR/ABL1 fusion. Both BCR/ABL1 fusion-positive cases presented with per-