-
[show abstract]
[hide abstract]
ABSTRACT: The characteristics of carbapenem-resistant P. aeruginosa (CRPA) isolates from Korea were investigated. Two major clones, CC235 and CC641, were identified. CC235, an important international clone, might have been imported recently in Korea as the clone displayed a homogeneous genotype, oprD mutation, and antimicrobial resistance profile. While 13 ST235 isolates harbored the blaIMP-6 gene, which conferred high-level meropenem resistance, CC641 isolates showed high biofilm-forming activity. CC235 and CC641 isolates showed distinct distribution of ferripyoverdine receptor type and virulence markers. While all CC235 isolates were the fpvAIIb type and exoS-/exoU+, CC641 isolates were exoS+/exoU-, and all but one showed the fpvAIII type. CC235 and CC641 isolates were also characterized by different extracellular protease activity; staphylolysin and elastase activities in CC235 and CC641, respectively. Two major CRPA clones in Korea seem to be predominant, reflecting their selective advantage by virtue of antimicrobial resistance, virulence, and biofilm-forming activity.
Journal of Medical Microbiology 04/2013; · 2.50 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Among 213 Pseudomonas aeruginosa isolates collected from 10 South Korean hospitals, 57 isolates (26.8%) were carbapenem-resistant. All but three of the isolates had a relevant decrease of oprD expression. However, decreased oprD expression was also detected in five of ten carbapenem-susceptible isolates. Outer membrane protein analysis confirmed porin loss in carbapenem-resistant P. aeruginosa isolates. Based on the mutations of oprD gene sequences, carbapenem-resistant P. aeruginosa isolates could be classified into five oprD mutational groups. However, there was no difference of OprD expression or carbapenem minimum inhibitory concentrations among the five mutational groups. Among the 57 carbapenem-resistant P. aeruginosa isolates, 41 (71.9%) overexpressed efflux systems or ampC. MexAB-OprM and AmpC overexpression (56.1% and 47.4%, respectively) was prevalent and was significantly associated with carbapenem resistance. However, no synergistic effect of efflux systems and AmpC on carbapenem resistance was evident. In conclusion, combination of several mutation-driven mechanisms leading to OprD inactivation and overexpression of efflux systems was the main carbapenem resistance mechanism, but acquisition of a transferable resistance determinant such as metallo-β-lactamase could be problematic in clinical settings in South Korea.
International journal of antimicrobial agents 05/2012; 40(2):168-72. · 3.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Emergence of polymyxin resistance in carbapenem-resistant isolates is a great concern in clinical settings because it may mean the end of treatment options against Gram-negative bacterial infections. Polymyxin-nonsusceptible and -susceptible Pseudomonas aeruginosa isolates resistant to carbapenems and harboring bla(IMP-6) were alternatively isolated from a patient. In vitro antimicrobial susceptibility testing, multilocus sequence typing, and pulsed-field gel electrophoresis were performed. Metallo-β-lactamase genes such as bla(IMP), bla(VIM), bla(SPM), bla(GIM), and bla(SIM) and bla(OXA-50) were detected by polymerase chain reaction. Sequences of 2-component systems, PmrAB and PhoPQ, were also determined. All showed ST235 and the same pulsotype. Amino acid substitutions were identified in PmrB and PhoP from polymyxin-nonsusceptible isolates. Colistin exposure might be associated with the recovery of polymyxin-nonsusceptible isolates in this patient.
Diagnostic microbiology and infectious disease 01/2012; 72(3):267-71. · 2.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The in vitro activity of colistin was evaluated against 215 nonduplicated Pseudomonas aeruginosa isolates, including 53 multidrug-resistant isolates, which were collected between 2006 and 2007 from nine tertiary care hospitals in Korea. Colistin-nonsusceptible P. aeruginosa (CNPA) isolates were genotyped using multilocus sequence typing. Sixteen (7.4%) CNPA isolates (minimum inhibitory concentration [MIC], >2 mg/l) were identified, including three resistant isolates. All but one of the MDR P. aeruginosa isolates was susceptible to colistin. Multilocus sequence typing analysis identified 12 sequence types (STs) among 16 CNPA isolates, indicating that colistin nonsusceptibility might arise independently. However, ST244 and ST292, which may be international clones, were found in multiple CNPA isolates. Our data indicate an increase of P. aeruginosa isolates with reduced colistin susceptibility, suggesting the need for continuous surveillance of P. aeruginosa.
Microbial drug resistance (Larchmont, N.Y.) 03/2011; 17(2):299-304. · 1.99 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Candidaemia associated with intravascular catheter-associated infections is of great concern due to the resulting high morbidity and mortality. The antibiotic lock technique (ALT) was previously introduced to treat catheter-associated bacterial infections without removal of catheter. So far, the efficacy of ALT against Candida infections has not been rigorously evaluated. We investigated in vitro activity of ALT against Candida biofilms formed by C. albicans, C. glabrata, and C. tropicalis using five antifungal agents (caspofungin, amphotericin B, itraconazole, fluconazole, and voriconazole). The effectiveness of antifungal treatment was assayed by monitoring viable cell counts after exposure to 1 mg/mL solutions of each antibiotic. Fluconazole, itraconazole, and voriconazole eliminated detectable viability in the biofilms of all Candida species within 7, 10, and 14 days, respectively, while caspofungin and amphotericin B did not completely kill fungi in C. albicans and C. glabrata biofilms within 14 days. For C. tropicalis biofilm, caspofungin lock achieved eradication more rapidly than amphotericin B and three azoles. Our study suggests that azoles may be useful ALT agents in the treatment of catheter-related candidemia.
Journal of Korean medical science 12/2010; 25(12):1722-6. · 0.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Erythromycin-resistant Streptococcus pneumoniae isolates containing both erm(B) and mef(A) genes have a higher rate of multidrug resistance (MDR). We investigated the relationships between the presence of erythromycin resistance determinants and the recombination rate. We determined the mutation and recombination frequencies of 46 S. pneumoniae isolates, which included 19 with both erm(B) and mef(A), nine with only erm(B), six with only mef(A), and 11 erythromycin-susceptible isolates. Mutation frequency values were estimated as the number of rifampin-resistant colonies as a proportion of total viable count. Genotypes and serotypes of isolates with the hyper-recombination phenotype were determined. Twelve S. pneumoniae isolates were hypermutable and four isolates were determined to have hyper-recombination frequency. Streptococcus pneumoniae isolates with both erm(B) and mef(A) genes did not show a high mutation frequency. In contrast, all isolates with a hyper-recombination phenotype contained both erm(B) and mef(A) genes. In addition, the recombination rate of isolates with both erm(B) and mef(A) genes was statistically higher than the rate of other isolates. The dual presence of erm(B) and mef(A) genes in some pneumococcal isolates may be associated with high recombination frequency. This may be one of the reasons for the frequent emergence of MDR in certain pneumococcal isolates.
FEMS Microbiology Letters 08/2010; 309(2):163-9. · 2.04 Impact Factor
-
Kwan Soo Ko, Ji-Young Lee,
Jin Yang Baek,
Ji-Yoeun Suh,
Mi Young Lee,
Ji Young Choi,
Joon-Sup Yeom,
Yeon-Sook Kim,
Sook-In Jung,
Sang Yop Shin,
Sang Taek Heo,
Ki Tae Kwon,
Jun Seong Son,
Shin-Woo Kim,
Hyun-Ha Chang,
Hyun Kyun Ki,
Doo Ryeon Chung,
Kyong Ran Peck,
Jae-Hoon Song
[show abstract]
[hide abstract]
ABSTRACT: To investigate the antimicrobial resistance, extended-spectrum beta-lactamases (ESBLs) and clones of Klebsiella pneumoniae isolates causing bacteraemia or urinary tract infection (UTI) in Korea, a total of 406 K. pneumoniae isolates from patients with bacteraemia (221 isolates) and UTI (185 isolates) were collected from 10 tertiary-care Korean hospitals from July 2006 to October 2007. In vitro antimicrobial susceptibility testing was performed for all isolates and ESBL production was tested. Multilocus sequence typing (MLST) analyses were performed to characterize genotypes of ESBL-producing K. pneumoniae isolates. PFGE was performed for sequence type 11 (ST11) isolates. Forty-seven UTI isolates (25.4 %) produced ESBLs, while 30 bacteraemia isolates (13.6 %) produced ESBLs (P=0.002). Among 77 ESBL-producing isolates, thirty-two (41.6 %) produced SHV-type ESBLs. bla(CTX-M) genes such as bla(CTX-M-14) and bla(CTX-M-15) were detected in 36.4 %. MLST and PFGE analyses showed that ST11 was dominant in ESBL-producing K. pneumoniae isolates causing UTI (57.4 %) and in those causing bacteraemia (70.0 %) and has been prevalent in Korean hospitals. ST11 isolates harbour a combination of different ESBL genes. The ST11 clone of ESBL-producing K. pneumoniae isolates prevails in Korea, but most isolates might acquire ESBL genes independently or several different clones might be distributed in Korea.
Journal of Medical Microbiology 04/2010; 59(Pt 7):822-8. · 2.50 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Nasal swabs were collected to isolate S. aureus in 296 children, who visited the pediatrics department with a variety of symptoms. Staphylococcus aureus was isolated from 95 children (32.1%). Of the isolates, 18 were methicillin-resistant S. aureus (MRSA) (18.9%). Antimicrobial susceptibility testing was performed for all S. aureus cultured and the molecular characteristics were investigated. Forty-nine spa types were identified among the S. aureus isolates, and were classified into 13 spa groups (A-L). The most prevalent clone (34 isolates, 35.8%) belonged to the spa group B (spa repeat motif, WG/FKAOMQ), which corresponded to sequence type 30 (ST30) and its variants. Sixteen different spa types, within the spa group B, suggested that this group has evolved over a long period of time. In addition, all S. aureus isolates belonging to the spa group B were methicillin-susceptible, indicating that this group might represent successful adaptation of this clone in the community setting with low antibiotic pressure. The most frequently found clone in the MRSA group was spa group C (spa repeat motif, DMGGM) and SCCmec type IVA, which represented half of the MRSA isolates and corresponded to ST72. ST5-MRSA-II, the most prevalent MRSA clone in Korean hospitals, was found in only two isolates. These findings suggest that strains of S. aureus nasal carriage in Korean children visiting an outpatient pediatric department were different from the strains identified in hospital infections.
Microbial Drug Resistance 04/2008; 14(1):37-44. · 2.15 Impact Factor
-
Jae-Hoon Song,
Kwan Soo Ko,
Mi Young Lee,
Sulhee Park,
Jin Yang Baek, Ji-Young Lee,
Sang Taek Heo,
Ki Tae Kwon,
Seong Yeol Ryu,
Won Sup Oh,
Kyong Ran Peck,
Nam Yong Lee
[show abstract]
[hide abstract]
ABSTRACT: In vitro activities of ertapenem and 11 other comparator agents were tested against 1025 isolates of respiratory pathogens collected from 12 Asian countries. Resistance rate to ertapenem was 1.2% in 602 isolates of Streptococcus pneumoniae (MIC(50), 0.06/MIC(90), 1 microg/mL). Ertapenem was also very active against penicillin-, ciprofloxacin-, erythromycin-, and multidrug-resistant pneumococcal isolates (resistance rate: 3.5%, 2.7%, 1.9%, and 2.7%, respectively). Ertapenem-resistant pneumococcal isolates were found only in Vietnam and Korea. Ertapenem resistance was not found in methicillin-susceptible Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis, and Klebsiella pneumoniae, including extended-spectrum beta-lactamase producers. In vitro data suggest that ertapenem could be a useful treatment option for community-acquired pneumonia.
Diagnostic Microbiology and Infectious Disease 01/2007; 56(4):445-50. · 2.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this study we evaluated the in vitro activities of cefditoren and 14 other comparator agents against 1025 isolates of major respiratory tract pathogens including Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Klebsiella pneumoniae and Staphylococcus aureus. Bacterial isolates were collected from 11 Asian countries. The majority of S. pneumoniae isolates (98.8%) were susceptible to cefditoren. The MIC(50) and MIC(90) values (minimum inhibitory concentrations for 50% and 90% of the organisms, respectively) of S. pneumoniae were <or=0.06 microg/mL and 1 microg/mL, respectively. These values were 2-32-fold lower than those of the other cephalosporins. Activity against S. pneumoniae was observed irrespective of penicillin or macrolide resistance. Cefditoren was also active against methicillin-susceptible S. aureus (100% susceptible; MIC(90)=1 microg/mL), H. influenzae (100% susceptible; MIC(90)<or=0.016 microg/mL) and M. catarrhalis (MIC(90)=0.016 microg/mL). However, the cefditoren MIC(90) of K. pneumoniae reached only 64 microg/mL (81.4% susceptible), which may be due to the high incidence of extended-spectrum beta-lactamases in Asian countries. Therefore, cefditoren should be considered as a therapeutic option for the treatment of respiratory tract infections in Asian countries.
International Journal of Antimicrobial Agents 07/2006; 28(1):14-8. · 4.13 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To investigate appropriate antimicrobial agents, the optimal concentration and treatment duration for the antibiotic lock technique (ALT) to treat catheter-related infections caused by Staphylococcus epidermidis and Staphylococcus aureus.
We evaluated the bacterial killing activity of vancomycin, teicoplanin, ciprofloxacin, rifampicin, cefazolin, gentamicin, nafcillin and erythromycin against biofilms formed by two strains of S. aureus and two strains of S. epidermidis. The effectiveness of the antibiotic lock was assayed after exposure to antibiotics (1, 5 and 10 mg/mL) for 1, 3, 5, 7, 10 or 14 days using an in vitro model of biofilms on polyurethane film.
The biofilms were completely sterile after exposure to vancomycin (5 mg/mL) for 5 days and teicoplanin (5 and 10 mg/mL) for 7 days. Ciprofloxacin and rifampicin (both 5 mg/mL) achieved eradication of the biofilms of both staphylococcal species more rapidly than vancomycin or teicoplanin. Significant biofilm eradication was not achieved with cefazolin, nafcillin, gentamicin and erythromycin at any of the time exposures examined.
The data suggest that 5 mg/mL vancomycin, ciprofloxacin or rifampicin can eradicate S. epidermidis and S. aureus biofilms within 5 days. These findings warrant prospective clinical trials for the evaluation of the clinical efficacy of ALT for less than 10 days.
Journal of Antimicrobial Chemotherapy 07/2006; 57(6):1110-5. · 5.07 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This study was undertaken to evaluate the in vitro activities of arbekacin-based combination regimens against vancomycin hetero-intermediate Staphylococcus aureus (hetero-VISA). Combinations of arbekacin with vancomycin, rifampin, ampicillin-sulbactam, teicoplanin, or quinupristin-dalfopristin against seven hetero-VISA strains and two methicillin-resistant S. aureus strains were evaluated by the time-kill assay. The combinations of arbekacin with vancomycin, teicoplanin, or ampicillin-sulbactam showed the synergistic interaction against hetero-VISA strains. Data suggest that these arbekacin-based combination regimens may be useful candidates for treatment options of hetero-VISA infections.
Journal of Korean Medical Science 05/2006; 21(2):188-92. · 0.99 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To find potential targets of novel antimicrobial agents, we identified essential genes of Streptococcus pneumoniae using comparative genomics and allelic replacement mutagenesis. We compared the genome of S. pneumoniae R6 with those of Bacillus subtilis, Enterococcus faecalis, Escherichia coli, and Staphylococcus aureus, and selected 693 candidate target genes with > 40% amino acid sequence identity to the corresponding genes in at least two of the other species. The 693 genes were disrupted and 133 were found to be essential for growth. Of these, 32 encoded proteins of unknown function, and we were able to identify orthologues of 22 of these genes by genomic comparisons. The experimental method used in this study is easy to perform, rapid and efficient for identifying essential genes of bacterial pathogens.
Molecules and Cells 06/2005; 19(3):365-74. · 2.18 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
Journal of Clinical Microbiology 06/2005; 43(5):2303-6. · 4.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To investigate the evolutionary pattern and genotypic characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains in the Asian region, 74 MRSA strains isolated from 12 Asian countries were analyzed by multilocus sequence typing (MLST) and SCCmec typing. Overall, a total of 16 genotypes based on sequence type and SCCmec types were identified among MRSA strains from Asian countries. Data revealed two major genotypes of MRSA strains in Asia, with unique geographic distributions. By MLST analysis, all strains from Korea and Japan except one belonged to clonal complex 5 (CC5) while most MRSA isolates from other Asian countries belonged to CC239. SCCmec typing showed that most isolates from Korea and Japan were SSmec type II whereas SCCmec type III (or IIIA) was the most common type in strains from other Asian countries. Our data documented a unique geographic distribution and evolutionary pattern of MRSA clones in Asia.
Journal of Clinical Microbiology 02/2005; 43(1):421-6. · 4.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: While ica gene of Staphylococcus epidermidis is known to undergo phase variation by insertion of IS256, the phenomenon in Staphylococcus aureus has not been evaluated. Six biofilm-positive strains were tested for the presence of biofilm-negative phase-variant strains by Congo red agar test. For potential phase-variant strains, pulsed-field gel electrophoresis was done to exclude the possibility of contamination. To investigate the mechanism of the biofilm-negative phase variation, PCR for each ica genes were done. Changes of ica genes detected by PCR were confirmed by southern hybridization, and their nucleotides were analyzed by DNA sequencing. Influence of ica genes and biofilm formation on capacity for adherence to biomedical material was evaluated by comparing the ability of adhering to polyurethane surface among a biofilm-negative phase-variant strain and its parent strain. A biofilm-negative phase-variant S. aureus strain was detected from 6 strains tested. icaC gene of the phase-variant strain was found to be inactivated by insertion of additional gene segment, IS256. The biofilm-negative phase-variant strain showed lower adhering capacity to polyurethane than its parent strain. This study shows that phase variation of ica gene occurs in S. aureus by insertion of IS256 also, and this biofilm-negative phase variation reduces adhering capacity of the bacteria.
Journal of Korean Medical Science 01/2005; 19(6):779-82. · 0.99 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This study was performed to evaluate the interaction of erythromycin or rifampin with vancomycin against Staphylococcus epidermidis biofilms.
Biofilm-forming S. epidermidis strains (ATCC 35983, 35984) and polyurethane (PU) sheets were incubated for the formation of bacterial biofilms. Biofilms on PU sheets were treated with various antibiotic regimens. The number of viable bacteria on the sheets was counted.
While erythromycin or vancomycin alone did not significantly reduce the biofilm bacterial concentration, the combination of vancomycin and erythromycin resulted in a clear reduction in bacterial concentration compared with the single agents. Rifampin was the most active single agent against biofilm-forming S. epidermidis, while the combination of rifampin and vancomycin showed further reduction in bacterial concentration.
These data suggest that the combination of erythromycin or rifampin and vancomycin is more effective than vancomycin alone in the treatment of biofilm infections caused by biofilm-forming S. epidermidis.
Chemotherapy 08/2003; 49(4):189-93. · 1.82 Impact Factor
