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1.  Evaluation of VITEK Mass Spectrometry (MS), a Matrix-Assisted Laser Desorption Ionization Time-of-Flight MS System for Identification of Anaerobic Bacteria 
Annals of Laboratory Medicine  2014;35(1):69-75.
By conventional methods, the identification of anaerobic bacteria is more time consuming and requires more expertise than the identification of aerobic bacteria. Although the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) systems are relatively less studied, they have been reported to be a promising method for the identification of anaerobes. We evaluated the performance of the VITEK MS in vitro diagnostic (IVD; 1.1 database; bioMérieux, France) in the identification of anaerobes.
We used 274 anaerobic bacteria isolated from various clinical specimens. The results for the identification of the bacteria by VITEK MS were compared to those obtained by phenotypic methods and 16S rRNA gene sequencing.
Among the 249 isolates included in the IVD database, the VITEK MS correctly identified 209 (83.9%) isolates to the species level and an additional 18 (7.2%) at the genus level. In particular, the VITEK MS correctly identified clinically relevant and frequently isolated anaerobic bacteria to the species level. The remaining 22 isolates (8.8%) were either not identified or misidentified. The VITEK MS could not identify the 25 isolates absent from the IVD database to the species level.
The VITEK MS showed reliable identifications for clinically relevant anaerobic bacteria.
PMCID: PMC4272968  PMID: 25553283
MALDI-TOF MS; VITEK MS; Anaerobic bacteria
2.  Antimicrobial Susceptibility of Clinical Isolates of Bacteroides fragilis Group Organisms Recovered from 2009 to 2012 in a Korean Hospital 
Annals of Laboratory Medicine  2014;35(1):94-98.
Periodic monitoring of antimicrobial resistance trends of clinically important anaerobic bacteria such as Bacteroides fragilis group organisms is required. We determined the antimicrobial susceptibilities of clinical isolates of B. fragilis group organisms recovered from 2009 to 2012 in a tertiary-care hospital in Korea.
A total of 180 nonduplicate clinical isolates of B. fragilis group organisms were collected in a tertiary care hospital. The species were identified by conventional methods: the ATB 32A rapid identification system (bioMérieux, France) and the Vitek MS matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (bioMérieux). Antimicrobial susceptibility was determined by the CLSI agar dilution method.
Imipenem and meropenem resistance rates were 0-6% for B. fragilis group isolates. The rate of resistance to piperacillin-tazobactam was 2% for B. fragilis and 0% for other Bacteroides species, but 17% for B. thetaiotaomicron isolates. High resistance rates to piperacillin (72% and 69%), cefotetan (89% and 58%), and clindamycin (83% and 69%) were observed for B. thetaiotaomicron and other Bacteroides spp. The moxifloxacin resistance rate was 27% for other Bacteroides spp. The MIC50 and MIC90 of tigecycline were 2-4 µg/mL and 8-16 µg/mL, respectively. No isolates were resistant to chloramphenicol or metronidazole.
Imipenem, meropenem, chloramphenicol, and metronidazole remain active against B. fragilis group isolates. Moxifloxacin and tigecycline resistance rates are 2-27% and 8-15% for B. fragilis group isolates, respectively.
PMCID: PMC4272972  PMID: 25553287
Bacteroides fragilis group; Antimicrobial resistance; Tigecycline; Moxifloxacin
3.  Bacteroides faecis and Bacteroides intestinalis Recovered from Clinical Specimens of Human Intestinal Origin 
Yonsei Medical Journal  2014;56(1):292-294.
We report three cases of recently named Bacteroides spp. isolates, two B. faecis isolates and one B. intestinalis isolate from clinical specimens of inpatients at a Korean tertiary-care hospital in 2011. All isolates were susceptible to piperacillin-tazobactam, imipenem, meropenem, chloramphenicol, and metronidazole.
PMCID: PMC4276769  PMID: 25510777
Bacteroides faecis; Bacteroides intestinalis
4.  Clonality and Resistome Analysis of KPC-Producing Klebsiella pneumoniae Strain Isolated in Korea Using Whole Genome Sequencing 
BioMed Research International  2014;2014:352862.
We analyzed the whole genome sequence and resistome of the outbreak Klebsiella pneumoniae strain MP14 and compared it with those of K. pneumoniae carbapenemase- (KPC-) producing isolates that showed high similarity in the NCBI genome database. A KPC-2-producing multidrug-resistant (MDR) K. pneumoniae clinical isolate was obtained from a patient admitted to a Korean hospital in 2011. The strain MP14 was resistant to all tested β-lactams including monobactam, amikacin, levofloxacin, and cotrimoxazole, but susceptible to tigecycline and colistin. Resistome analysis showed the presence of β-lactamase genes including blaKPC-2, blaSHV-11, blaTEM-169, and blaOXA-9. MP14 also possessed aac(6′-)Ib, aadA2, and aph(3′-)Ia as aminoglycoside resistance-encoding genes, mph(A) for macrolides, oqxA and oqxB for quinolone, catA1 for phenicol, sul1 for sulfonamide, and dfrA12 for trimethoprim. Both SNP tree and cgMLST analysis showed the close relatedness with the KPC producers (KPNIH strains) isolated from an outbreak in the USA and colistin-resistant strains isolated in Italy. The plasmid-scaffold genes in plasmids pKpQil, pKpQil-IT, pKPN3, or pKPN-IT were identified in MP14, KPNIH, and Italian strains. The KPC-2-producing MDR K. pneumoniae ST258 stain isolated in Korea was highly clonally related with MDR K. pneumoniae strains from the USA and Italy. Global spread of KPC-producing K. pneumoniae is a worrying phenomenon.
PMCID: PMC4106114  PMID: 25105122
5.  Increase in the Prevalence of Carbapenem-Resistant Acinetobacter Isolates and Ampicillin-Resistant Non-Typhoidal Salmonella Species in Korea: A KONSAR Study Conducted in 2011 
Infection & Chemotherapy  2014;46(2):84-93.
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.
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.
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.
PMCID: PMC4091365  PMID: 25024870
Antimicrobial resistance surveillance; KONSAR; Staphylococcus; Acinetobacter; Pseudomonas aeruginosa
6.  First Outbreak of KPC-2-Producing Klebsiella pneumoniae Sequence Type 258 in a Hospital in South Korea 
Journal of Clinical Microbiology  2013;51(11):3877-3879.
In this study, we report the first outbreak of KPC-2-producing Klebsiella pneumoniae isolates from three patients admitted to a neurosurgery department in a South Korean teaching hospital. Multilocus sequence typing showed that the isolates were identical to the previous KPC producers in South Korea and other countries, suggesting clonal spread.
PMCID: PMC3889788  PMID: 24006005
7.  Complete Genome Sequence of the Bacteriophage YMC01/01/P52 PAE BP, Which Causes Lysis of Verona Integron-Encoded Metallo-β-Lactamase-Producing, Carbapenem-Resistant Pseudomonas aeruginosa 
Journal of Virology  2012;86(24):13876-13877.
Multidrug-resistant Pseudomonas aeruginosa commonly causes serious nosocomial infections. In this study, a novel lytic bacteriophage belonging to a member of the family Podoviridae, YMC01/01/P52 PAE BP, which infects carbapenem-resistant Pseudomonas aeruginosa, was isolated and characterized. YMC01/01/P52 PAE BP genome was analyzed by whole-genome sequencing and putative function identification. The bacteriophage genome consists of a double-stranded linear DNA genome of 49,381 bp with a GC content of 62.16%.
PMCID: PMC3503104  PMID: 23166271
8.  Complete Genome Sequence of the Podoviral Bacteriophage YMC/09/02/B1251 ABA BP, Which Causes the Lysis of an OXA-23-Producing Carbapenem-Resistant Acinetobacter baumannii Isolate from a Septic Patient 
Journal of Virology  2012;86(22):12437-12438.
The emergence of carbapenem-resistant Acinetobacter baumannii, responsible for causing nosocomial infections, has been becoming a significant global health issue. In this article, we report the complete genome sequence of bacteriophage Bϕ-B1251 (YMC/09/02/B1251 ABA BP), which causes lysis of a carbapenem-resistant A. baumannii strain. The bacteriophage belongs to the family Podoviridae and has a double-stranded circular DNA genome with a length of 45,364 bp and a 39.05% G+C content. Genome analysis showed that it had no similarity to other previously reported bacteriophages capable of infecting A. baumannii.
PMCID: PMC3486505  PMID: 23087105
9.  Evaluation of Double-Disk Potentiation and Disk Potentiation Tests Using Dipicolinic Acid for Detection of Metallo-β-Lactamase-Producing Pseudomonas spp. and Acinetobacter spp. 
Journal of Clinical Microbiology  2012;50(10):3227-3232.
Accurate detection of metallo-β-lactamase (MBL)-producing Pseudomonas spp. and Acinetobacter spp. became very important with the increasing prevalence of carbapenem-nonsusceptible clinical isolates. The performance of phenotypic MBL detection methods may depend on the types of MBL and the characteristics of the isolates. A high false-positive rate is a problem with EDTA-based MBL detection methods. We evaluated the performance of double-disk potentiation tests (DDPTs) and disk potentiation tests (DPTs) with dipicolinic acid (DPA) using 44 isolates of Pseudomonas spp. and Acinetobacter spp. producing IMP-1-like, VIM-2-like, and SIM-1 type MBLs. Also, we characterized P. aeruginosa isolates with positive imipenem (IPM)-DPA DDPT, but negative meropenem (MEM)-DPA DDPT, and determined possibility of improving a DDPT by using MacConkey agar. Among five different DDPT methods, the IPM-DPA 250-μg method showed the highest sensitivity (97.7%) and specificity (100%). Among four DPT tests, the highest sensitivity (100%) was shown by the IPM-EDTA 1,900-μg disk method, but the specificity was very low (11.4%). Five of six P. aeruginosa isolates with false-negative DDPTs with MEM-DPA 250-μg disks carried blaIMP-6, and the high level resistance to MEM (MIC ≥ 512 μg/ml) was reduced by the presence of phenylalanine arginine β-naphtylamide. Improvement of DDPTs was observed when MacConkey agar was used instead of Mueller-Hinton agar. In conclusion, DPA is a better MBL inhibitor than EDTA for detection of Pseudomonas spp. and Acinetobacter spp. with IMP-1-like, VIM-2-like, and SIM-1-type MBLs. In DPA DDPTs, IPM disks perform better than MEM disks when the isolates are highly resistant to MEM due to the overexpression of efflux pumps.
PMCID: PMC3457450  PMID: 22837321
10.  CTX-M-55-Type Extended-Spectrum β-lactamase-Producing Shigella sonnei Isolated from a Korean Patient Who Had Travelled to China 
Annals of Laboratory Medicine  2013;33(2):141-144.
We report a case of CTX-M-55-type extended-spectrum β-lactamase (ESBL)-producing Shigella sonnei infection in a 27-year-old Korean woman who had traveled to China. The patient was admitted to the hospital due to abdominal pain, watery diarrhea, and fever (39.3℃). S. sonnei was isolated from her stool specimens, and the pathogen was found to be resistant to cefotaxime due to CTX-M-55-type ESBL. Insertion sequence (IS)Ecp1 was found upstream of the blaCTX-M-55 gene. The blaCTX-M-55 gene was transferred from the S. sonnei isolate to an Escherichia coli J53 recipient by conjugation. Pulsed-field gel electrophoresis and Southern blotting revealed that the blaCTX-M-55 gene was located on a plasmid of approximately 130 kb.
PMCID: PMC3589641  PMID: 23483349
CTX-M-55; Shigella sonnei; ESBL
11.  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.
PMCID: PMC3546106  PMID: 23341713
Stenotrophomonas maltophilia; Combination Drug Therapy; Trimethoprim-Sulfamethoxazole; Ticarcillin-Clavulanate
12.  Nosocomial Clustering of NDM-1-Producing Klebsiella pneumoniae Sequence Type 340 Strains in Four Patients at a South Korean Tertiary Care Hospital 
Journal of Clinical Microbiology  2012;50(4):1433-1436.
In November 2010, NDM-1-producing Klebsiella pneumoniae (NDMKP) was identified for the first time in South Korea from four patients with no history of traveling abroad who stayed for 21 to 205 days in a tertiary care hospital. All were sequence type (ST) 340 and had nearly identical XbaI pulsed-field gel electrophoresis (PFGE) patterns. The blaNDM-1-carrying plasmids were in the IncN group, with sizes ranging from 50 to 200 kb. These findings suggest that NDMKP had already been introduced into South Korea before this clustering was found.
PMCID: PMC3318568  PMID: 22259206
13.  Evaluation of the Xpert Clostridium difficile Assay for the Diagnosis of Clostridium difficile Infection 
Annals of Laboratory Medicine  2012;32(5):355-358.
Infection with Clostridium difficile is a growing concern because of the increasing prevalence and spread of nosocomial infections. Emergence of the hypervirulent 027/NAP1/BI strain is also notable. Existing diagnostic methods have low sensitivity or are time-consuming. Therefore, establishing a rapid and accurate microbiological diagnostic assay is needed. We evaluated the Xpert C. difficile assay (Xpert CD assay; Cepheid, USA) to detect toxigenic C. difficile. This assay is a real-time multiplex PCR assay that can be used to detect toxigenic C. difficile strains and differentiate the C. difficile presumptive 027/NAP1/BI strain. A total of 253 loose stool specimens were collected and toxigenic cultures, VIDAS C. difficile A & B assays (VIDAS CDAB assay; bioMérieux, France), and the Xpert CD assay were performed. In comparison to toxigenic cultures, the sensitivity, specificity, and positive and negative predictive values were 100%, 94.6%, 83.1%, and 100%, respectively, for the Xpert CD assay and 40.8%, 98.0%, 100%, and 88.9%, respectively, for VIDAS CDAB assay. Because of the low prevalence of the PCR ribotype 027 in Korea, the evaluation of the usefulness of the Xpert CD assay for screening for the 027 strain was limited. The Xpert CD assay provides great sensitivity in diagnosing toxigenic C. difficile infection. In addition, this method has excellent usability because it is simple and fast.
PMCID: PMC3427823  PMID: 22950071
Clostridium difficile; Real-time PCR; Enzyme immunoassay
14.  Biochemical Characterization of the TEM-107 Extended-Spectrum β-Lactamase in a Klebsiella pneumoniae Isolate from South Korea▿ 
Antimicrobial Agents and Chemotherapy  2011;55(12):5930-5932.
The TEM-107 extended-spectrum β-lactamase detected in a Klebsiella pneumoniae clinical isolate had a Gly238Ser substitution compared to the TEM-43 β-lactamase. The MIC of ceftazidime was higher (64 μg/ml) than that of cefotaxime (2 μg/ml) for the isolate. Clavulanic acid reduced the MIC of ceftazidime 64-fold.
PMCID: PMC3232759  PMID: 21911565
15.  Antimicrobial Susceptibility of Stenotrophomonas maltophilia Isolates from a Korean Tertiary Care Hospital 
Yonsei Medical Journal  2012;53(2):439-441.
We determined the antimicrobial susceptibility of 90 clinical isolates of Stenotrophomonas maltophilia collected in 2009 at a tertiary care hospital in Korea. Trimethoprim-sulfamethoxazole, minocycline, and levofloxacin were active against most of the isolates tested. Moxifloxacin and tigecycline were also active and hold promise as therapeutic options for S. maltophilia infections.
PMCID: PMC3282950  PMID: 22318836
Stenotrophomonas maltophilia; antimicrobial susceptibility; trimethoprim-sulfamethoxazole; levofloxacin; minocycline
16.  Multidrug-Resistant Acinetobacter spp.: Increasingly Problematic Nosocomial Pathogens 
Yonsei Medical Journal  2011;52(6):879-891.
Pathogenic bacteria have increasingly been resisting to antimicrobial therapy. Recently, resistance problem has been relatively much worsened in Gram-negative bacilli. Acinetobacter spp. are typical nosocomial pathogens causing infections and high mortality, almost exclusively in compromised hospital patients. Acinetobacter spp. are intrinsically less susceptible to antibiotics than Enterobacteriaceae, and have propensity to acquire resistance. A surveillance study in Korea in 2009 showed that resistance rates of Acinetobacter spp. were very high: to fluoroquinolone 67%, to amikacin 48%, to ceftazidime 66% and to imipenem 51%. Carbapenem resistance was mostly due to OXA type carbapenemase production in A. baumannii isolates, whereas it was due to metallo-β-lactamase production in non-baumannii Acinetobacter isolates. Colistin-resistant isolates were rare but started to be isolated in Korea. Currently, the infection caused by multidrug-resistant A. baumannii is among the most difficult ones to treat. Analysis at tertiary care hospital in 2010 showed that among the 1,085 isolates of Acinetobacter spp., 14.9% and 41.8% were resistant to seven, and to all eight antimicrobial agents tested, respectively. It is known to be difficult to prevent Acinetobacter spp. infection in hospitalized patients, because the organisms are ubiquitous in hospital environment. Efforts to control resistant bacteria in Korea by hospitals, relevant scientific societies and government agencies have only partially been successful. We need concerted multidisciplinary efforts to preserve the efficacy of currently available antimicrobial agents, by following the principles of antimicrobial stewardship.
PMCID: PMC3220254  PMID: 22028150
Acinetobacter baumannii; multidrug resistance; OXA type carbapenemase; metallo-β-lactamase
17.  Further Increases in Carbapenem-, Amikacin-, and Fluoroquinolone-Resistant Isolates of Acinetobacter spp. and P. aeruginosa in Korea: KONSAR Study 2009 
Yonsei Medical Journal  2011;52(5):793-802.
The increasing prevalence of antimicrobial resistant bacteria has become a serious worldwide problem. The aim of this study was to analyze antimicrobial resistance data generated in 2009 by hospitals and commercial laboratories participating in the Korean Nationwide Surveillance of Antimicrobial Resistance program.
Materials and Methods
Susceptibility data were collected from 24 hospitals and two commercial laboratories. In the analysis, resistance did not include intermediate susceptibility. Duplicate isolates were excluded from the analysis of hospital isolates, but not from the commercial laboratory isolates.
Among the hospital isolates, methicillin-resistant Staphylococcus aureus, penicillin G-non-susceptible Streptococcus pneumoniae based on meningitis breakpoint, and ampicillin-resistant Enterococcus faecium remained highly prevalent. The proportion of vancomycin-resistant E. faecium gradually increased to 29%. Ceftazidime-resistant Escherichia coli and Klebsiella pneumoniae increased to 17% and 33%, respectively, and fluoroquinolone-resistant K. pneumoniae, Acinetobacter spp. and Pseudomonas aeruginosa increased to 33%, 67% and 39%, respectively. Amikacin-resistant Acinetobacter spp. increased to 48%. Imipenem-resistant Acinetobacter spp. and P. aeruginosa increased to 51% and 26%, respectively. Higher resistance rates were observed in intensive care unit (ICU) isolates than in non-ICU isolates among the isolates from hospitals. Resistance rates were higher in hospital isolates than in clinic isolates among the isolates from commercial laboratories.
Among the hospital isolates, ceftazidime-resistant K. pneumoniae and fluoroquinolone-resistant K. pneumoniae, Acinetobacter spp., and P. aeruginosa further increased. The increase in imipenem resistance was slight in P. aeruginosa, but drastic in Acinetobacter spp. The problematic antimicrobial-organism combinations were much more prevalent among ICU isolates.
PMCID: PMC3159946  PMID: 21786445
Antimicrobial resistance surveillance; fluoroquinolone resistance; imipenem resistance; KONSAR; Staphylococcus; Acinetobacter spp.; P. aeruginosa
18.  Metallo-β-Lactamase Production by Pseudomonas otitidis: a Species-Related Trait ▿  
Susceptibility to several β-lactams and β-lactamase production was investigated in a collection of 20 strains of Pseudomonas otitidis, a new Pseudomonas species that has been recently recognized in association with otic infections in humans. All strains appeared to be susceptible to piperacillin, cefotaxime, ceftazidime, and aztreonam, while resistance or decreased susceptibility to carbapenems was occasionally observed. All strains were found to express metallo-β-lactamase (MBL) activity and to carry a new subclass B3 MBL gene, named blaPOM, that appeared to be highly conserved in this species. P. otitidis, therefore, is the first example of a pathogenic Pseudomonas species endowed with a resident MBL. The POM-1 protein from P. otitidis type strain MCC10330 exhibits the closest similarity (60 to 64%) to the L1 MBL of Stenotrophomonas maltophilia. Expression in Escherichia coli and Pseudomonas aeruginosa revealed that, similar to L1 and other subclass B3 MBLs, POM-1 confers decreased susceptibility or resistance to carbapenems, penicillins, and cephalosporins but not to aztreonam. Expression of the POM MBL in P. otitidis is apparently constitutive and, in most strains, does not confer a carbapenem-resistant phenotype. However, a strong inoculum size effect was observed for carbapenem MICs, and carbapenem-resistant mutants could be readily selected upon exposure to imipenem, suggesting that carbapenem-based regimens should be considered with caution for P. otitidis infections.
PMCID: PMC3019635  PMID: 21060106
19.  Emergence of Clostridium difficile Ribotype 027 in Korea 
Clostridium difficile infection (CDI) has markedly risen and is associated with hypervirulent ribotype 027 outbreaks in North America and Europe since 2003. The aims of this study were to determine the prevalence of ribotype 027 among C. difficile isolates in Korea, to characterize the ribotype 027 isolates, and to determine the clinical severity of CDI in patients infected with these isolates.
A total of 1,251 isolates of C. difficile recovered from stool specimens of suspected CDI patients at two tertiary-care hospitals and one commercial laboratory between 2002 and 2009. Genes for toxin A (tcdA), toxin B (tcdB), and binary toxin (cdtA and cdtB) were detected by PCR. Mutation in the tcdC gene was detected by sequencing after PCR amplification. For molecular genotyping, we performed PCR-ribotyping, pulsed-field gel electrophoresis (PFGE), and multilocus variable-number tandem-repeat analysis (MLVA). Minimum inhibitory concentrations of moxifloxacin were determined using Etest strips (AB bioMérieux, Sweden).
We identified 7 isolates as ribotype 027. These isolates had the same tcdC mutation as the epidemic strain, and 6 of them were resistant to moxifloxacin. The isolates were categorized into 3 different PFGE types and 7 different MLVA types. All the 7 cases had occurred sporadically.
C. difficile ribotype 027 is uncommon, but it has emerged in Korea. The spread of this ribotype should be closely monitored in order to avoid an outbreak of CDI in Korea.
PMCID: PMC3129351  PMID: 21779194
Clostridium difficile; PCR-ribotype 027; Pulsed-field gel electrophoresis; Multilocus variable-number tandem-repeat analysis
20.  Subcutaneous Phaeohyphomycosis Caused by Phaeoacremonium Species in a Kidney Transplant Patient: The First Case in Korea 
Phaeohyphomycosis is a subcutaneous infection caused by dark pigmented fungi, including fungi of the species Phaeoacremonium, Alternaria, Exophiala, and Pyrenochaeta. In August 2005, a 54-yr-old man who had received a renal transplant 5 yr ago was admitted to our hospital with a subcutaneous mass on the third finger of the right hand; the mass had been present for several months. He had been receiving immunosuppressive agents for several years. He underwent excision of the mass, which was followed by aspiration of the wound for bacterial and fungal cultures. Many fungal hyphae were observed on the histology slide treated with periodic acid-Schiff stain. A few white waxy colonies with a woolly texture grew on the Sabouraud dextrose agar at 30℃ and changed to dark brown in color. Nucleotide sequencing of internal transcribed spacer regions revealed 100% homology to the Phaeoacremonium aleophilum anamorph and Togninia minima teleomorph (514 bp/514 bp). The patient completely recovered after wide surgical excision. Here, we report the first case of phaeohyphomycosis caused by Phaeoacremonium species in a kidney transplant patient in Korea.
PMCID: PMC3129353  PMID: 21779196
Subcutaneous phaeohyphomycosis; Phaeoacremonium species; Renal transplantation; Immunosuppressive agents
21.  Comparative In Vitro Activities of Torezolid (DA-7157) against Clinical Isolates of Aerobic and Anaerobic Bacteria in South Korea ▿  
Antimicrobial Agents and Chemotherapy  2010;54(12):5381-5386.
Resistance of Gram-positive pathogens to first-line antimicrobial agents has been increasing in many parts of the world. We compared the in vitro activities of torezolid with those of other antimicrobial agents, including linezolid, against clinical isolates of major aerobic and anaerobic bacteria. Torezolid had an MIC90 of ≤0.5 μg/ml for the Gram-positive bacterial isolates tested and was more potent than either linezolid or vancomycin.
PMCID: PMC2981271  PMID: 20837761
22.  Various penA mutations together with mtrR, porB and ponA mutations in Neisseria gonorrhoeae isolates with reduced susceptibility to cefixime or ceftriaxone 
To examine mutations within the penA, mtrR, porB, ponA and pilQ genes of Neisseria gonorrhoeae to determine their contribution to cephalosporin resistance.
A total of 46 N. gonorrhoeae isolates with reduced susceptibility to cefixime or ceftriaxone (MICs ≥ 0.12 mg/L) and two susceptible isolates were selected. The full sequence of penA and partial sequences previously reported as hot mutation sites of the other genes were analysed. Genotyping by N. gonorrhoeae multiantigen sequence typing (NG-MAST) was also performed.
A mosaic penicillin-binding protein 2 (PBP 2) was found in a single isolate that exhibited the highest cefixime MIC (0.5 mg/L). The majority of the isolates with reduced susceptibility to cephalosporins contained non-mosaic PBP 2 sequences, of which PBP 2 pattern XIII was most common (28/46). All isolates with reduced susceptibility to cephalosporins also had mtrR and porB mutations. Two susceptible isolates had the PBP 2 pattern XIV and an incomplete MtrR protein, which was a new mutation. Isolates with identical PBP 2 patterns comprised multiple NG-MAST sequence types.
Reduced susceptibility of N. gonorrhoeae to ceftriaxone and cefixime was associated with diverse penA mutations, particularly PBP 2 pattern XIII containing an Ala-501→Val substitution, together with mtrR and porB mutations. The existence of only one strain having the mosaic penA sequence indicated that ceftriaxone and cefixime resistance in Korea is mostly not associated with a mosaic penA sequence. Highly heterogeneous NG-MAST sequence types excluded the clonal expansion of a particular subtype.
PMCID: PMC2837549  PMID: 20093260
penicillin binding protein 2; genotyping; antibiotic resistance; cephalosporins
23.  Antimicrobial Susceptibility Patterns for Recent Clinical Isolates of Anaerobic Bacteria in South Korea▿  
We determined the antimicrobial susceptibilities of 255 clinical isolates of anaerobic bacteria collected in 2007 and 2008 at a tertiary-care hospital in South Korea. Piperacillin-tazobactam, cefoxitin, imipenem, and meropenem were highly active β-lactam agents against most of the isolates tested. The rates of resistance of Bacteroides fragilis group organisms and anaerobic Gram-positive cocci to moxifloxacin were 11 to 18% and 0 to 27%, respectively.
PMCID: PMC2935019  PMID: 20585132
24.  Increase of Ceftazidime- and Fluoroquinolone-Resistant Klebsiella pneumoniae and Imipenem-Resistant Acinetobacter spp. in Korea: Analysis of KONSAR Study Data from 2005 and 2007 
Yonsei Medical Journal  2010;51(6):901-911.
Antimicrobial resistance monitoring could be a useful source of information for treating and controlling nosocomial infections. We analyzed antimicrobial resistance data generated by Korean Hospitals and by a commercial laboratory in 2005 and 2007.
Materials and Methods
Susceptibility data for 2005 and 2007 were collected from 37 and 41 hospitals, respectively, and from one commercial laboratory. Intermediate susceptibility was not included in the calculation of resistance rates.
Methicillin-resistant Staphylococcus aureus (MRSA) (64%), third-generation cephalosporin-resistant Klebsiella pneumoniae (29%), fluoroquinolone-resistant Escherichia coli (27%), Pseudomonas aeruginosa (33%), and Acinetobacter spp. (48%), and amikacin-resistant P. aeruginosa (19%) and Acinetobacter spp. (37%) were prevalent in hospitals in 2007. A gradual increase of vancomycin-resistant Enterococcus faecium and imipenem-resistant Acinetobacter spp. was observed. Higher incidences of third-generation cephalosporin-resistant E. coli and K. pneumoniae and imipenem-resistant P. aeruginosa were found in the commercial laboratory than in the hospitals.
Methicillin-resistant S. aureus, third-generation cephalosporin-resistant K. pneumoniae, and fluoroquinolone-resistant E. coli, P. aeruginosa and Acinetobacter spp. remain prevalent in Korea, while the incidence of vancomycin-resistant E. faecium and imipenem-resistant Acinetobacter spp. has increased gradually. The higher prevalences of third-generation cephalosporin-resistant E. coli and K. pneumoniae, and imipenem-resistant P. aeruginosa in the commercial laboratory are a new concern.
PMCID: PMC2995968  PMID: 20879058
Antimicrobial resistance surveillance; Korea; vancomycin resistance; fluoroquinolone resistance; imipenem resistance; MRSA; P. aeruginosa; Acinetobacter spp.
25.  Three Cases of Moraxella osloensis Meningitis: A Difficult Experience in Species Identification and Determination of Clinical Significance 
Journal of Korean Medical Science  2010;25(3):501-504.
We had three cases of Moraxella osloensis meningitis. The species identification was impossible by conventional and commercial phenotypic tests. However, we could identify the species using the 16S rRNA gene sequencing. Determination of clinical significance was difficult in one patient. All three patients recovered by appropriate antimicrobial therapy.
PMCID: PMC2826726  PMID: 20191057
Moraxella osloensis; Meningitis; 16S Ribosomal RNA Gene Sequencing

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