Asia Pacific Foundation for Infectious Diseases APFID

Seoul, South Korea

Asia Pacific Foundation for Infectious Diseases APFID

Seoul, South Korea
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Song J.-H.,Sungkyunkwan University | Song J.-H.,Asia Pacific Foundation for Infectious Diseases APFID | Dagan R.,Soroka University Medical Center | Dagan R.,Pfizer | And 3 more authors.
Vaccine | Year: 2012

Streptococcus pneumoniae (SP) causes significant burden of disease, including invasive pneumococcal disease and noninvasive diseases such as pneumonia and acute otitis media. SP has at least 93 different capsular serotypes, with the various serotypes having different propensities for producing disease or developing antibiotic resistance. An increase in the prevalence of antibiotic-resistant SP serotypes has been observed globally. The objective of this paper was to examine the relationship between antibiotic resistance and SP serotypes, with a primary focus on studies published in the past 10 years. Changing trends in antibiotic resistance and serotype distribution during this time, including those before and after the introduction of 7-valent pneumococcal conjugate vaccine (PCV7), were analyzed. Factors that influence the prevalence of antibiotic-resistant serotypes include antibiotic selection pressure, the use of PCV7, and the emergence and spread of antibiotic-resistant clones. The emergence of multidrug resistant serotype 19A is of particular concern. Antibiotic-resistant SP is a global problem that must be addressed through multiple strategies, including national vaccination programs, antibiotic control programs, and ongoing surveillance. © 2012 Elsevier Ltd.


Song J.-H.,Sungkyunkwan University | Song J.-H.,Asia Pacific Foundation for Infectious Diseases APFID | Chung D.R.,Sungkyunkwan University
Infectious Disease Clinics of North America | Year: 2010

Pneumonia is the most common infection that is the leading cause of death. The increasing antimicrobial resistance in major respiratory pathogens such as Streptococcus pneumoniae, Staphylococcus aureus and gram-negative bacteria has severely restricted the treatment options. Respiratory infections caused by multidrug-resistant bacteria are associated with a greater likelihood of inappropriate antimicrobial therapy and poor clinical outcome. Especially, treatment of infections caused by pandrug-resistant gram-negative bacteria is a major challenge. Continuous efforts to control the global spread of drug-resistant bacteria are essential. © 2010 Elsevier Inc.


Kim D.H.,Sungkyunkwan University | Park Y.K.,Sungkyunkwan University | Ko K.S.,Sungkyunkwan University | Ko K.S.,Asia Pacific Foundation for Infectious Diseases APFID
Antimicrobial Agents and Chemotherapy | Year: 2012

AbaR resistance islands in Acinetobacter baumannii isolates from South Korea were investigated. AbaR4-type resistance islands, including bla OXA-23-containing Tn2006, interrupted the comM gene in A. baumannii ST75 isolates. However, Tn2006 was not identified within AbaR resistance islands of ST138 isolates, although the blaOXA-23 gene was detected in them. The similar structures of resistance islands suggest that most carbapenem-resistant A. baumannii isolates in South Korea have originated from the same ancestor with a globally disseminated clone, GC II. Copyright © 2012, American Society for Microbiology. All Rights Reserved.


Kang C.-I.,Sungkyunkwan University | Song J.-H.,Sungkyunkwan University | Song J.-H.,Asia Pacific Foundation for Infectious Diseases APFID
Infection and Chemotherapy | Year: 2013

Antimicrobial resistance has become one of the most serious public health concerns worldwide. Although circumstances may vary by region or country, it is clear that some Asian countries are epicenters of resistance, having seen rapid increases in the prevalence of antimicrobial resistance of major bacterial pathogens. In these locations, however, the public health infrastructure to combat this problem is very poor. The prevalence rates of methicillin-resistant Staphylococcus aureus (MRSA), macrolide-resistant Streptococcus pneumoniae, and multidrug-resistant enteric pathogens are very high due to the recent emergence of extremely drug-resistant gram-negative bacilli in Asia. Because antimicrobial options for these pathogens are extremely limited, infections caused by antimicrobial-resistant bacteria are often associated with inappropriate antimicrobial therapy and poor clinical outcomes. Physicians should be aware of the current epidemiological status of resistance and understand the appropriate use of antimicrobial agents in clinical practice. This review focuses on describing the epidemiology and clinical implications of antimicrobial-resistant bacterial infections in Asian countries. © 2013 by The Korean Society of Infectious Diseases.


Ko K.S.,Sungkyunkwan University | Ko K.S.,Asia Pacific Foundation for Infectious Diseases APFID | Baek J.Y.,Asia Pacific Foundation for Infectious Diseases APFID | Song J.-H.,Asia Pacific Foundation for Infectious Diseases APFID | Song J.-H.,Sungkyunkwan University
Journal of Clinical Microbiology | Year: 2013

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 ofthe "serotype 6E" isolates. Copyright © 2013, American Society for Microbiology.


Lee J.-Y.,Sungkyunkwan University | Ko K.S.,Sungkyunkwan University | Ko K.S.,Asia Pacific Foundation for Infectious Diseases APFID
Diagnostic Microbiology and Infectious Disease | Year: 2014

To comprehend the resistance of colistin resistance, we investigated the relationships between amino acid alterations and expression of PmrAB and PhoPQ and colistin resistance in 16 colistin-nonsusceptible clinical Pseudomonas aeruginosa isolates. In addition, we obtained induced colistin-resistant mutants and their colistin-susceptible revertants. Expression levels of the pmrA, phoP, parR, cprR, and pmrH genes were determined for them. Nine amino acid substitutions unique to 10 colistin-nonsusceptible P. aeruginosa (CNPA) isolates were identified: 7 in PmrB and 1 each in PmrA and PhoQ. However, 6 CNPA isolates did not show amino acid substitutions compared with colistin-susceptible P. aeruginosa isolates. Among 16 CNPA isolates, 7 and 8 isolates displayed activated expression of pmrA and phoP, respectively. Activated expression of pmrA and/or phoP was identified in 13 isolates of CNPA isolates, but some had no noticeable PmrAB and PhoPQ amino acid substitutions. In addition, in vitro selected colistin-resistant mutants (P5R and P155R) showed higher expression level in pmrA, phoP, and pmrH than their parent strains (P5 and P155) and colistin-susceptible, revertant strains (P5R-rev and P155R-rev). However, expression of the parR and cprR genes was not consistent. Our data may indicate that amino acid substitutions of PmrAB or PhoPQ do not have an immediate connection with decreased susceptibility of colistin in P. aeruginosa isolates, although activated expression of pmrAB and/or phoPQ resulting in overexpression of pmrH may be required for colistin resistance. Expression of pmrAB or phoPQ related with colistin nonsusceptibility may not explained by a single mechanism, which may suggest that colistin resistance appears easily by diverse pathways in clinical settings as well as in laboratory. © 2014 Elsevier Inc.


Song J.-H.,Sungkyunkwan University | Song J.-H.,Asia Pacific Foundation for Infectious Diseases APFID
Expert Review of Respiratory Medicine | Year: 2013

Antimicrobial resistance and serotypes in Streptococcus pneumoniae have been evolving with the widespread use of antibiotics and the introduction of pneumococcal conjugate vaccines (PCV). Particularly, among various types of antimicrobial resistance, macrolide resistance has most remarkably increased in many parts of the world, which has been reported to be >70% among clinical isolates from Asian countries. Penicillin resistance has dramatically decreased among nonmeningeal isolates due to the changes in resistance breakpoints, although resistance to other β-lactams such as cefuroxime has increased. Multidrug resistance became a serious concern in the treatment of invasive pneumococcal diseases, especially in Asian countries. After PCV7 vaccination, serotype 19A has emerged as an important cause of invasive pneumococcal diseases which was also associated with increasing prevalence of multidrug resistance in pneumococci. Widespread use of PCV13, which covers additional serotypes 3, 6A and 19A, may contribute to reduce the clonal spread of drug-resistant 19A pneumococci. © 2013 Informa UK Ltd.


Shin J.,Sungkyunkwan University | Choi M.-J.,Sungkyunkwan University | Ko K.S.,Sungkyunkwan University | Ko K.S.,Asia Pacific Foundation for Infectious Diseases APFID
Journal of Antimicrobial Chemotherapy | Year: 2012

Objectives: The purpose of this study was to investigate variations in IncF plasmids and the genetic environments of bla CTX-M-15 in CTX-M-15-producing Escherichia coli and Klebsiella pneumoniae isolates from South Korea. Methods: A total of 56 E. coli and 15 K. pneumoniae isolates, which were previously characterized for CTX-M-15 production, sequence type by multilocus sequence typing and replicon type, were included in this study. Replicon sequence typing for IncF plasmids was performed and the genetic environments of bla CTX-M-15 were determined using PCR and sequencing. Results: A total of 34 and 10 IncF-replicon sequence types (RSTs) were identified among the E. coli and K. pneumoniae isolates, respectively. Only eight and four IncF-RSTs were found in multiple isolates of E. coli and K. pneumoniae, respectively. No common IncF-RSTs were found between E. coli and K. pneumoniae isolates. Five and three different bla CTX-M-15 genetic environments were identified in E. coli and K. pneumoniae isolates, respectively. Even in the same E. coli clone, diverse IncF-RSTs and bla CTX-M-15 genetic environments were identified. Conclusions: Diverse IncF plasmids have incorporated into diverse strains of E. coli and K. pneumoniae, contributing to the spread of the CTX-M-15 extended-spectrum β-lactamase in South Korea. It can also be inferred that bla CTX-M-15 has not been transferred directly from E. coli to K. pneumoniae. © The Author 2012. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.


Shin J.,Sungkyunkwan University | Kim D.H.,Sungkyunkwan University | Ko K.S.,Sungkyunkwan University | Ko K.S.,Asia Pacific Foundation for Infectious Diseases APFID
Journal of Infection | Year: 2011

Objective: Recently, CTX-M-15-producing Enterobacteriaceae has disseminated worldwide. To better understand the success of CTX-M-15-type extended-spectrum β-lactamase, we compared the CTX-M-15-producing Escherichia coli and Klebsiella pneumoniae isolates with CTX-M-14-producing E. coli and K. pneumoniae isolates that had been more prevalent before the recent increase of CTX-M-15 in Korea. Methods: Eighty-nine CTX-M-producing E. coli bloodstream infection isolates and 33 K. pneumoniae bloodstream infection isolates were collected in 2008 from nine hospitals in Korea. In vitro susceptibility testing and multilocus sequence typing were performed for all isolates. Phylogenetic groupings and distribution of virulence determinants and addiction systems were examined for only E. coli isolates. Results: Among the 89 CTX-M-producing E. coli isolates, 54 isolates (60.7%) contained blaCTx-M-15 and blaCTx-M-14 was identified in 31 isolates (34.8%). Among 33 CTX-M-producing K. pneumoniae isolates, blaCTx-M-14 and blaCTx-M-15 were identified in 18 (54.5%) and 15 (45.5%) isolates, respectively. While CTX-M-14- and CTX-M-15-producing E. coli isolates displayed similar antimicrobial resistance rates, CTX-M-15-producing K. pneumoniae isolates showed significantly higher resistance rates of ciprofloxacin and piperacillin-tazobactam than CTX-M-14-producing isolates. ST131 and ST405 were the main clones in both CTX-M-14- and CTX-M-15-producing E. coli isolates. Although the frequency of virulence determinants was similar between two E. coli groups, ST131 and ST405 isolates producing CTX-M-15 showed higher frequency of determinants. In addition, CTX-M-15-producing E. coli isolates showed higher prevalence of addiction systems, particularly vagCD. ST405 showed the highest prevalence rates among main E. coli clones. In K. pneumoniae, ST15 and ST11, with high resistance rates, were the main clones of CTX-M-15-producing isolates, but no main clones was found among CTX-M-14-producing isolates because of extreme diversity. Conclusions: Rapid increase of CTX-M-15-producing E. coli isolates was due to certain clone with high frequency of virulence determinants and addiction systems. High antimicrobial resistance rates of CTX-M-15-producing K. pneumoniae isolates may contribute to their increase. © 2011 The British Infection Association.


Song J.-H.,Sungkyunkwan University | Song J.-H.,Asia Pacific Foundation for Infectious Diseases APFID | Baek J.Y.,Asia Pacific Foundation for Infectious Diseases APFID | Ko K.S.,Asia Pacific Foundation for Infectious Diseases APFID | Ko K.S.,Sungkyunkwan University
Journal of Clinical Microbiology | Year: 2011

Recently, Streptococcus pneumoniae serotypes 6C and 6D have been identified. It is thought that they emerged by the replacement of wciN β 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 wciN β. 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. Copyright © 2011, American Society for Microbiology. All Rights Reserved.

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