Performance evaluation of a new matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, ASTA MicroIDSys system, in bacterial identification against clinical isolates of anaerobic bacteria.

Introduction: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been introduced for bacterial identification. The ASTA MicroIDSys system (ASTA, Suwon, Korea) is a new MALDI-TOF MS system developed for species identification of microorganisms. We evaluated the performance of MicroIDSys against clinical isolates of anaerobic bacteria.

Modification and evaluation of the Triton Hodge test for screening carbapenemase-producing Enterobacteriaceae.

Detection of carbapenemase-producing Enterobacteriaceae (CPE) has become critical for appropriate antimicrobial therapy and for controlling the spread of infection. We evaluated Triton Hodge test (THT) for screening CPE. A spreader can be used to apply more constant volume of Triton on whole surface of Mueller-Hinton agar (MHA), or alternatively, a 10-μL inoculating loop can be used to apply a 20% Triton solution lineally.

CTX-M-55-type extended-spectrum β-lactamase-producing Shigella sonnei isolated from a Korean patient who had travelled to China.

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℃).

Gene cloning and characterization of MdeA, a novel multidrug efflux pump in Streptococcus mutans.

Multidrug resistance, especially multidrug efflux mechanisms that extrude structurally unrelated cytotoxic compounds from the cell by multidrug transporters, is a serious problem and one of the main reasons for the failure of therapeutic treatment of infections by pathogenic microorganisms as well as of cancer cells. Streptococcus mutans is considered one of the primary causative agents of dental caries and periodontal disease, which comprise the most common oral diseases. A fragment of chromosomal DNA from S.

Clonal change of blaSIM-1-carrying Acinetobacter spp. from 2003 to 2008 in the hospital where it was initially discovered.

SIM-1 metallo-β-lactamase was first discovered from carbapenem-resistant Acinetobacter spp. isolated in a Korean University Hospital in 2003, and was recently reported to have been discovered in A. baylyi isolated in nearby China.

Molecular mechanisms of carbapenem resistance in Enterobacter cloacae clinical isolates from Korea and clinical outcome.

We investigated the molecular mechanisms of carbapenem resistance in clinical isolates of Enterobacter cloacae and their clinical characteristics. Nonreplicable E. cloacae isolates were recovered from six cancer patients and one patient with liver cirrhosis at a tertiary-care hospital in Korea between 2002 and 2009.

Comparison of the genetic structures surrounding qnrA1 in Korean Enterobacter cloacae and Chinese Escherichia coli strains isolated in the early 2000s: evidence for qnrA mobilization via Inc HI2 type plasmid.

The flanking genetic structure of qnrA1 in Korean Enterobacter loacae was identical to that of the Chinese Escherichia coli strain, the first qnrA1-carrying strain reported in Asia. Analysis of restriction enzyme sites and Southern blot hybridization results showed that qnrA1 was transferred between E. cloacae and E.

Biochemical characterization of the TEM-107 extended-spectrum β-lactamase in a Klebsiella pneumoniae isolate from South Korea.

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.

Chromosomal cephalosporinase in Enterobacter hormaechei as an ancestor of ACT-1 plasmid-mediated AmpC β-lactamase.

In this study of the diversity of AmpC β-lactamase in clinical isolates of Enterobacter spp., a strain was found carrying the plasmid-mediated AmpC β-lactamase ACT-1 gene on its chromosome. The strain was identified as Enterobacter hormaechei using phylogenetic analysis of 16S rRNA and hsp60 genes.

Comparative in vitro activities of torezolid (DA-7157) against clinical isolates of aerobic and anaerobic bacteria in South Korea.

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 MIC(90) of ≤0.

Improved performance of the modified Hodge test with MacConkey agar for screening carbapenemase-producing Gram-negative bacilli.

The detection of carbapenemases in Gram-negative bacilli is important for optimal patient treatment and to control spread of the resistance. The modified Hodge test can detect carbapenemase-producing Gram-negative bacilli. In this study, we compared the performance of MacConkey agar and Mueller-Hinton agar for metallo-β-lactamase (MBL) and OXA carbapenemase screening.

Characteristics of clinical isolates of Acinetobacter genomospecies 10 carrying two different metallo-beta-lactamases.

Acquired metallo-beta-lactamase (MBL) production is an important mechanism of carbapenem resistance. To our knowledge, carriage of two different MBLs has not been described previously in Acinetobacter spp. We present the characteristics of five Acinetobacter isolates carrying two different MBL genes.

Genetic diversity of chromosomal metallo-beta-lactamase genes in clinical isolates of Elizabethkingia meningoseptica from Korea.

This study was performed to characterize the chromosomal metallo-beta-lactamases (MBLs) of Elizabethkingia meningoseptica isolated from Korea and to propose a clustering method of BlaB and GOB MBLs based on their amino acid similarities. Chromosomal MBL genes were amplified by PCR from 31 clinical isolates of E. meningoseptica.

New cfiA variant and novel insertion sequence elements in carbapenem-resistant Bacteroides fragilis isolates from Korea.

Of 276 nonduplicate Bacteroides fragilis clinical isolates recovered from 1997 to 2004, 3 were resistant to carbapenem. cepA and cfiA alleles were detected by polymerase chain reaction in 240 (87.0%) and 11 (4.

Role of OXA-23 and AdeABC efflux pump for acquiring carbapenem resistance in an Acinetobacter baumannii strain carrying the blaOXA-66 gene.

This study was performed to determine the mechanisms for acquiring carbapenem resistance in six clinical isolates of Acinetobacter baumannii. All isolates showed similar SmaI-macrorestriction patterns with less than 3 band differences by PFGE. The isolates showed a high level resistance (>32 mg/L) to both imipenem and meropenem by Etest.

Resistance trends of Bacteroides fragilis group over an 8-year period, 1997-2004, in Korea.

Background: Bacteroides fragilis group organisms are the most frequently isolated anaerobes in human infections. Increasing resistance to various antimicrobial agents is a significant problem in choosing appropriate antimicrobial agents to treat anaerobic infections. Periodic monitoring of the regional resistance trends of B.

[In vitro activity of arbekacin against clinical isolates of Staphylococcus species and gram-negative bacilli].

Background: Methicillin-resistant Staphylococcus aureus (MRSA) and some gram-negative bacilli are very prevalent nosocomial pathogens, commonly causing mixed infections, and are often resistant to multiple drugs. Arbekacin is an aminoglycoside used for the treatment of MRSA infections, but is also active against some gram-negative bacilli. The aim of this study was to determine in vitro activity of arbekacin against recent clinical isolates of staphylococci and gram-negative bacilli.

In vitro activities of CG400549, a novel FabI inhibitor, against recently isolated clinical staphylococcal strains in Korea.

The in vitro activities of CG400549, a novel FabI inhibitor, were compared to those of linezolid and commonly used antimicrobials against recent bacterial isolates. CG400549 had an MIC(90) of 0.5 microg/ml for Staphylococcus aureus strains and was more potent than either linezolid or vancomycin.

Reduced imipenem susceptibility in Klebsiella pneumoniae clinical isolates with plasmid-mediated CMY-2 and DHA-1 beta-lactamases co-mediated by porin loss.

We investigated the resistance mechanisms and clonality among 42 imipenem-non-susceptible Klebsiella pneumoniae isolated at a tertiary care hospital in Korea. Two isolates had bla(VIM-2) alleles, whereas bla(CMY-2)- and bla(DHA-1)-like alleles were detected in 24 and 16 isolates, respectively, with these enzymes confirmed by sequencing for representative isolates. Transfer of bla(CMY-2) and bla(DHA-1) was achieved by conjugation.

Prevalence of inducible clindamycin resistance in staphylococcal isolates at a Korean tertiary care hospital.

Clindamycin resistance in Staphylococcus species can be either constitutive or inducible. Inducible resistance cannot be detected by the conventional antimicrobial susceptibility test. In this study, we determined the prevalence of inducible clindamycin resistance in staphylococcal isolates at a Korean tertiary care hospital.

Dissemination of 16S rRNA methylase-mediated highly amikacin-resistant isolates of Klebsiella pneumoniae and Acinetobacter baumannii in Korea.

Novel 16S rRNA methylase-mediated high-level resistance to amikacin and arbekacin has been reported recently in clinical isolates of Gram-negative bacilli only from several countries. We tested amikacin- or arbekacin-nonsusceptible Gram-negative bacilli isolated in 2003 and 2005 at a tertiary-care hospital in Korea by polymerase chain reaction to detect 16S rRNA methylase genes. armA alleles were detected in 14 isolates of Klebsiella pneumoniae, 10 other species of Enterobacteriaceae, and 16 Acinetobacter baumannii, whereas the rmtB allele was detected in 1 K.

Increasing prevalence and diversity of metallo-beta-lactamases in Pseudomonas spp., Acinetobacter spp., and Enterobacteriaceae from Korea.

Among imipenem-nonsusceptible isolates, acquired metallo-beta-lactamase genes were detected in 36 of 581 (6.2%) Pseudomonas aeruginosa isolates, 42 of 44 (95.4%) other Pseudomonas species, and 136 of 513 (26.