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1.  Capsular Gene Sequences and Genotypes of “Serotype 6E” Streptococcus pneumoniae Isolates 
Journal of Clinical Microbiology  2013;51(10):3395-3399.
To characterize Streptococcus pneumoniae “serotype 6E,” complete cps loci were sequenced. The capsular genes of “serotype 6E” isolates differed much from those of serotypes 6A and 6B. We identified 10 additional “serotype 6E” isolates, which are not confined to a restricted geographic locality. Most of these “serotype 6E” isolates belonged to sequence type 90 and its single-locus variants. The homogeneity of their genetic background and cps loci suggests a recent origin of the “serotype 6E” isolates.
doi:10.1128/JCM.01645-13
PMCID: PMC3811659  PMID: 23824778
2.  First Imported Case of Skin Infection Caused by PVL-positive ST30 Community-Associated Methicillin-Resistant Staphylococcus aureus Clone in a Returning Korean Traveler from the Philippines 
Journal of Korean Medical Science  2013;28(7):1100-1102.
Although pandemic community-associated (CA-) methicillin-resistant Staphylococcus aureus (MRSA) ST30 clone has successfully spread into many Asian countries, there has been no case in Korea. We report the first imported case of infection caused by this clone in a Korean traveler returning from the Philippines. A previously healthy 30-yr-old Korean woman developed a buttock carbuncle while traveling in the Philippines. After coming back to Korea, oral cephalosporin was given by a primary physician without any improvement. Abscess was drained and MRSA strain isolated from her carbuncle was molecularly characterized and it was confirmed as ST30-MRSA-IV. She was successfully treated with vancomycin and surgery. Frequent international travel and migration have increased the risk of international spread of CA-MRSA clones. The efforts to understand the changing epidemiology of CA-MRSA should be continued, and we should raise suspicion of CA-MRSA infection in travelers with skin infections returning from CA-MRSA-endemic countries.
doi:10.3346/jkms.2013.28.7.1100
PMCID: PMC3708085  PMID: 23853497
Staphylococcus aureus; Methicillin Resistance; Community-Acquired Infections; Carbuncle; Travel
3.  Bacteremic Pneumonia Caused by Extensively Drug-Resistant Streptococcus pneumoniae 
Journal of Clinical Microbiology  2012;50(12):4175-4177.
The emergence of antimicrobial resistance threatens the successful treatment of pneumococcal infections. Here we report a case of bacteremic pneumonia caused by an extremely drug-resistant strain of Streptococcus pneumoniae, nonsusceptible to at least one agent in all classes but vancomycin and linezolid, posing an important new public health threat in our region.
doi:10.1128/JCM.01642-12
PMCID: PMC3502956  PMID: 23052301
4.  A third case of USA300 community-associated methicillin-resistant Staphylococcus aureus infection in Korea 
doi:10.3904/kjim.2013.28.2.258
PMCID: PMC3604620  PMID: 23524494
Staphylococcus aureus; Methicillin resistance; Community-acquired infections; Genotype
5.  Prosthetic Valve Endocarditis Due to Neisseria skkuensis, a Novel Neisseria Species 
Journal of Clinical Microbiology  2012;50(8):2820-2822.
We describe the first reported case of endocarditis due to Neisseria skkuensis. The organism from the blood cultures taken on admission day was identified initially as unidentified Gram-negative cocci by Vitek2. Finally, it was identified as Neisseria skkuensis by 16 rRNA gene sequence analysis.
doi:10.1128/JCM.00676-12
PMCID: PMC3421520  PMID: 22675133
6.  First Report of Vancomycin-Intermediate Resistance in Sequence Type 72 Community Genotype Methicillin-Resistant Staphylococcus aureus 
Journal of Clinical Microbiology  2012;50(7):2513-2514.
Vancomycin-intermediate resistance has not been previously reported among sequence type 72 (ST72) methicillin-resistant Staphylococcus aureus (MRSA) isolates of SCCmec type IV (ST72-MRSA-IV), which are distinctive community genotype strains in Korea. We report the first case of vancomycin treatment failure due to development of vancomycin-intermediate resistance in infection caused by an ST72-MRSA-IV isolate.
doi:10.1128/JCM.00590-12
PMCID: PMC3405585  PMID: 22553243
7.  Multidrug-Resistant Streptococcus pneumoniae Serotype 6D Clones in South Korea 
Journal of Clinical Microbiology  2012;50(3):818-822.
To investigate the characteristics of main Streptococcus pneumoniae clones of serotype 6D (ST282 and ST3171) in South Korea, antimicrobial susceptibility testing was performed, and 11 genes around the cps locus were sequenced on ST2826D, ST31716D, and ST816A isolates. The antimicrobial susceptibility patterns were very similar between clones belonging to the same clonal complex, ST816A and ST2826D; nonsusceptibilities to penicillin and cefuroxime, high MICs of ceftriaxone, and high resistance rates to trimethoprim-sulfamethoxazole. However, ST31716D isolates showed resistance to only macrolides and clindamycin. The sequences of 11 genes around the cps locus indicated the same genetic backgrounds between the ST816A and ST2826D isolates. On the other hand, ST31716D isolates showed nucleotide and amino acid differences from ST816A and ST2826D isolates in most genes, indicating a different genetic background. The mosaic structure of dexB gene in ST2826D isolates indicated that recombination might occur in the dexB gene. Our results suggest that the multidrug-resistant ST2826D pneumococcal clone has emerged by serial genetic recombination, including capsular switch.
doi:10.1128/JCM.05895-11
PMCID: PMC3295089  PMID: 22170935
8.  Post-influenza Pneumonia Caused by the USA300 Community-Associated Methicillin-Resistant Staphylococcus aureus in Korea 
Journal of Korean Medical Science  2012;27(3):313-316.
Panton-Valentine leukocidin (PVL)-positive USA300 clone has been the most successful community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) clone spreading in North America. In contrast, PVL-negative ST72-CA-MRSA has been predominant in Korea, and there has been no report of infections by the USA300 strain except only one case report of perianal infection. Here, we describe the first case of pneumonia caused by the USA300 strain following pandemic influenza A (H1N1) in Korea. A 50-year-old man was admitted with fever and cough and chest radiograph showed pneumonic consolidation at the right lower lung zone. He received a ventilator support because of respiratory failure. PCR for pandemic influenza A (H1N1) in nasopharyngeal swab was positive, and culture of sputum and endotracheal aspirate grew MRSA. Typing of the isolate revealed that it was PVL-positive, ST 8-MRSA-SCCmec type IV. The analysis of the PFGE patterns showed that this isolate was the same pulsotype as the USA300 strain.
doi:10.3346/jkms.2012.27.3.313
PMCID: PMC3286780  PMID: 22379344
Influenza, Human; Methicillin-Resistant Staphylococcus aureus; Pneumonia
9.  Comparison of Capsular Genes of Streptococcus pneumoniae Serotype 6A, 6B, 6C, and 6D Isolates▿ 
Journal of Clinical Microbiology  2011;49(5):1758-1764.
Recently, Streptococcus pneumoniae serotypes 6C and 6D have been identified. It is thought that they emerged by the replacement of wciNβ in the capsular loci of serotypes 6A and 6B, respectively. However, their evolution has not been unveiled yet. To investigate the evolution of four serotypes of S. pneumoniae serogroup 6, four genes of the capsular polysaccharide synthesis (cps) locus, wchA, wciN, wciO, and wciP, of isolates of S. pneumoniae serotypes 6A, 6B, 6C, and 6D were sequenced. Multilocus sequence typing (MLST) was performed to investigate their genetic backgrounds. The wchA gene of serotype 6C and 6D isolates was distinct from that of serotype 6A and 6B isolates, which may suggest cotransfer of wchA with wciNβ. Otherwise, serotypes 6C and 6D displayed different genetic backgrounds from serotypes 6A and 6B, which was suggested by MLST analysis. In addition, serotype 6C isolates showed distinct wciP polymorphisms from other serotypes, which also indicated that serotype 6C had not recently originated from serotype 6A. Although serotype 6D shared the same amino acid polymorphisms of wciO with serotype 6B, wciP of serotype 6D differed from that of serotype 6B. The data indicate the implausibility of the scenario of a recent emergence of the cps locus of serotype 6D by genetic recombination between serotypes 6B and 6C. In addition, five serotype 6A and 6B isolates (6X group) displayed cps loci distinct from those of other isolates. The cps locus homogeneity and similar sequence types in MLST analysis suggest that most of the 6X group of isolates originated from the same ancestor and that the entire cps locus might have recently been transferred from an unknown origin. Serotype 6B isolates showed two or more cps locus subtypes, indicating a recombination-mediated mosaic structure of the cps locus of serotype 6B. The collective data favor the emergence of cps loci of serotypes 6A, 6B, 6C, and 6D by complicated recombination.
doi:10.1128/JCM.02628-10
PMCID: PMC3122669  PMID: 21411593
11.  Comparison of Genotypes and Enterotoxin Genes Between Staphylococcus aureus Isolates from Blood and Nasal Colonizers in a Korean Hospital 
Journal of Korean Medical Science  2009;24(4):585-591.
In this study, we investigated the genetic background of 70 Staphylococcus aureus isolates (36 methicillin-resistant S. aureus [MRSA] and 34 methicillin-susceptible S. aureus [MSSA]) obtained from blood at a Korean tertiary-care hospital, using spa typing, multilocus sequence typing, and SCCmec typing. In addition, the prevalence of enterotoxin (sea, seb, sec, sed, see, seg, seh, sei, and sek), tst, and pvl genes among the samples was assessed via polymerase chain reaction, and the results were compared with those of 95 isolates of S. aureus obtained from nasal swabs. All MRSA isolates from blood, except one, belonged to three major clones: sequence type (ST)5-MRSA-II, ST72-MRSA-II (or IVA), and ST239-MRSA-III, among which ST5-MRSA-II was the predominant clone. The prevalence of enterotoxin genes in the S. aureus isolates obtained from blood differed significantly from those from the nasal swabs for the sea, seb, sec, and seh gene. In particular, the seb and sec genes were detected exclusively in the MRSA isolates of ST5 or spa-CC002, thereby suggesting the co-adaptation of virulence genes with the genetic background and their contribution to biological fitness.
doi:10.3346/jkms.2009.24.4.585
PMCID: PMC2719184  PMID: 19654937
Enterotoxin Genes; Staphylococcus aureus; Bacteremia; Nasal Carriage
12.  Molecular Characterization of Vancomycin-Resistant Enterococcus faecium Isolates from Korea 
Journal of Clinical Microbiology  2005;43(5):2303-2306.
A total of 98 vancomycin-resistant Enterococcus faecium (VREF) isolates from four tertiary-care hospitals in Korea during the period between 1998 and 2004 were analyzed for genotypic characteristics using the multiplex PCR, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and esp gene analysis. Ninety-two isolates of VREF with VanA phenotype and five of six isolates with VanB phenotype possessed the vanA gene. MLST analysis revealed 9 sequence types (STs), which belonged to a single clonal complex (CC78, clonal lineage C1). Five strains showing incongruence between phenotype and genotype (VanB-vanA) did not belong to the same genotypic clone. The esp gene was detected in all VREF strains, showing 12 different esp repeat profiles. Data suggest that an epidemic clonal group of VREF, CC78 with esp gene, is also present in Asia and has differentiated into multiple diverse genotypic clones during the evolutionary process.
doi:10.1128/JCM.43.5.2303-2306.2005
PMCID: PMC1153736  PMID: 15872259
13.  Unique Variations of pbp2b Sequences in Penicillin-Nonsusceptible Streptococcus pneumoniae Isolates from Korea 
Journal of Clinical Microbiology  2004;42(4):1746-1750.
pbp2b gene alterations were analyzed in 102 clinical isolates of Streptococcus pneumoniae (30 penicillin susceptible, 23 intermediate, and 49 resistant) from Korea. On the basis of PBP2B amino acid sequences, penicillin-nonsusceptible isolates of S. pneumoniae belonged to six groups, and 76% of the isolates in groups I to IV showed the same divergent block of amino acid alterations. Thirteen isolates (group II) also possessed a divergent block that was identical to that of Streptococcus oralis. The pbp2b genes of most Korean isolates showed novel mosaic mutations due to horizontal gene transfer. The Thr252→Ala substitution, previously thought to be associated only with penicillin-nonsusceptible strains, was also found in three penicillin-susceptible strains. On the basis of their pbp2b nucleotide sequences, all penicillin-nonsusceptible isolates can be detected by multiplex PCR, which can be used as a novel method for detection of antibiotic-resistant pneumococcal strains in clinical specimens.
doi:10.1128/JCM.42.4.1746-1750.2004
PMCID: PMC387593  PMID: 15071038
14.  Changing Trends in Antimicrobial Resistance and Serotypes of Streptococcus pneumoniae Isolates in Asian Countries: an Asian Network for Surveillance of Resistant Pathogens (ANSORP) Study 
Antimicrobial resistance in Streptococcus pneumoniae remains a serious concern worldwide, particularly in Asian countries, despite the introduction of heptavalent pneumococcal conjugate vaccine (PCV7). The Asian Network for Surveillance of Resistant Pathogens (ANSORP) performed a prospective surveillance study of 2,184 S. pneumoniae isolates collected from patients with pneumococcal infections from 60 hospitals in 11 Asian countries from 2008 to 2009. Among nonmeningeal isolates, the prevalence rate of penicillin-nonsusceptible pneumococci (MIC, ≥4 μg/ml) was 4.6% and penicillin resistance (MIC, ≥8 μg/ml) was extremely rare (0.7%). Resistance to erythromycin was very prevalent in the region (72.7%); the highest rates were in China (96.4%), Taiwan (84.9%), and Vietnam (80.7%). Multidrug resistance (MDR) was observed in 59.3% of isolates from Asian countries. Major serotypes were 19F (23.5%), 23F (10.0%), 19A (8.2%), 14 (7.3%), and 6B (7.3%). Overall, 52.5% of isolates showed PCV7 serotypes, ranging from 16.1% in Philippines to 75.1% in Vietnam. Serotypes 19A (8.2%), 3 (6.2%), and 6A (4.2%) were the most prominent non-PCV7 serotypes in the Asian region. Among isolates with serotype 19A, 86.0% and 79.8% showed erythromycin resistance and MDR, respectively. The most remarkable findings about the epidemiology of S. pneumoniae in Asian countries after the introduction of PCV7 were the high prevalence of macrolide resistance and MDR and distinctive increases in serotype 19A.
doi:10.1128/AAC.05658-11
PMCID: PMC3294909  PMID: 22232285

Results 1-14 (14)