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Keiichi Hiramatsu - One of the best experts on this subject based on the ideXlab platform.

  • new trends in staphylococcus aureus infections glycopeptide resistance in hospital and Methicillin resistance in the community
    Current Opinion in Internal Medicine, 2002
    Co-Authors: Keiichi Hiramatsu, Keiko Okuma, Munetaka Yamamoto, Satoshi Hori, Maria Kapi
    Abstract:

    Purpose of review Methicillin-resistant Staphylococcus aureus is prevalent in hospitals throughout the world, and we have got used to its presence in daily clinical practice. However, Methicillin-resistant S. aureus has not remained static over the past four decades, but seems to be evolving in unfamiliar directions. This review focuses on recent findings on two directions of Methicillin-resistant S. aureus evolution: the acquisition of multiple antibiotic resistance in the hospital and the trend towards Methicillin-resistant S. aureus as a community pathogen. Recent findings We looked at reports on glycopeptide resistance in S. aureus and those on community-acquired Methicillin-resistant S. aureus strains, with some references of historical value to explain the entire picture of this ‘new field’ of the Methicillin-resistant S. aureus problem. Summary The references given here (excluding some of low credibility) attest the increasing awareness of the two conspicuous problems concerning Methicillin-resistant S. aureus infection. One is the increasing trend of glycopeptide-resistance, making difficult the successful treatment of multi-drug-resistant Methicillin-resistant S. aureus infection in the hospital. On the other hand, non-multi-drug-resistant Methicillin-resistant S. aureus strains are emerging as novel threats in the community, the genetic analysis of which indicates that they are independent clones from those found in hospitals.

  • the emergence and evolution of Methicillin resistant staphylococcus aureus
    Trends in Microbiology, 2001
    Co-Authors: Keiichi Hiramatsu, Makoto Kuroda
    Abstract:

    Abstract Significant advances have been made in recent years in our understanding of how Methicillin resistance is acquired by Staphylococcus aureus . Integration of a staphylococcal cassette chromosome mec (SCC mec ) element into the chromosome converts drug-sensitive S . aureus into the notorious hospital pathogen methicilin-resistant S . aureus (MRSA), which is resistant to practically all β-lactam antibiotics. SCC mec is a novel class of mobile genetic element that is composed of the mec gene complex encoding Methicillin resistance and the ccr gene complex that encodes recombinases responsible for its mobility. These elements also carry various resistance genes for non-β-lactam antibiotics. After acquiring an SCC mec element, MRSA undergoes several mutational events and evolves into the most difficult-to-treat pathogen in hospitals, against which all extant antibiotics including vancomycin are ineffective. Recent epidemiological data imply that MRSA has embarked on another evolutionary path as a community pathogen, as at least one novel SCC mec element seems to have been successful in converting S . aureus strains from the normal human flora into MRSA.

  • genetic organization of the chromosome region surrounding meca in clinical staphylococcal strains role of is431 mediated meci deletion in expression of resistance in meca carrying low level Methicillin resistant staphylococcus haemolyticus
    Antimicrobial Agents and Chemotherapy, 2001
    Co-Authors: Yuki Katayama, Keiichi Hiramatsu
    Abstract:

    We report on the structural diversity of mecA gene complexes carried by 38 Methicillin-resistant Staphylococcus aureus and 91 Methicillin-resistant coagulase-negative Staphylococcus strains of seven different species with a special reference to its correlation with phenotypic expression of Methicillin resistance. The most prevalent and widely disseminated mec complex had the structure mecI-mecR1-mecA-IS431R (or IS431mec), designated the class A mecA gene complex. In contrast, in S. haemolyticus, mecA was bracketed by two copies of IS431, forming the structure IS431L-mecA-IS431R. Of the 38 S. haemolyticus strains, 5 had low-level Methicillin resistance (MIC, 1 to 4 mg/liter) and characteristic heterogeneous Methicillin resistance as judged by population analysis. In these five strains, IS431L was located to the left of an intact mecI gene, forming the structure IS431L-class A mecA-gene complex. In other S. haemolyticus strains, IS431L was associated with the deletion of mecI and mecR1, forming the structure IS431L-ΔmecR1-mecA-IS431mec, designated the class C mecA gene complex. Mutants with the class C mecA gene complex were obtained in vitro by selecting strain SH621, containing the IS431L-class A mecA gene complex with low concentrations of Methicillin (1 and 3 mg/liter). The mutants had intermediate level of Methicillin resistance (MIC, 16 to 64 mg/liter). The mecA gene transcription was shown to be derepressed in a representative mutant strain, SH621-37. Our study indicated that the mecI-encoded repressor function is responsible for the low-level Methicillin resistance of some S. haemolyticus clinical strains and that the IS431-mediated mecI gene deletion causes the expression of Methicillin resistance through the derepression of mecA gene transcription.

  • genetic organization of the chromosome region surrounding meca in clinical staphylococcal strains role of is431 mediated meci deletion in expression of resistance in meca carrying low level Methicillin resistant staphylococcus haemolyticus
    Antimicrobial Agents and Chemotherapy, 2001
    Co-Authors: Yuki Katayama, Teruyo Ito, Keiichi Hiramatsu
    Abstract:

    We report on the structural diversity of mecA gene complexes carried by 38 Methicillin-resistant Staphylococcus aureus and 91 Methicillin-resistant coagulase-negative Staphylococcus strains of seven different species with a special reference to its correlation with phenotypic expression of Methicillin resistance. The most prevalent and widely disseminated mec complex had the structure mecI-mecR1-mecA-IS431R (or IS431mec), designated the class A mecA gene complex. In contrast, in S. haemolyticus, mecA was bracketed by two copies of IS431, forming the structure IS431L-mecA-IS431R. Of the 38 S. haemolyticus strains, 5 had low-level Methicillin resistance (MIC, 1 to 4 mg/liter) and characteristic heterogeneous Methicillin resistance as judged by population analysis. In these five strains, IS431L was located to the left of an intact mecI gene, forming the structure IS431L-class A mecA-gene complex. In other S. haemolyticus strains, IS431L was associated with the deletion of mecI and mecR1, forming the structure IS431L-DeltamecR1-mecA-IS431mec, designated the class C mecA gene complex. Mutants with the class C mecA gene complex were obtained in vitro by selecting strain SH621, containing the IS431L-class A mecA gene complex with low concentrations of Methicillin (1 and 3 mg/liter). The mutants had intermediate level of Methicillin resistance (MIC, 16 to 64 mg/liter). The mecA gene transcription was shown to be derepressed in a representative mutant strain, SH621-37. Our study indicated that the mecI-encoded repressor function is responsible for the low-level Methicillin resistance of some S. haemolyticus clinical strains and that the IS431-mediated mecI gene deletion causes the expression of Methicillin resistance through the derepression of mecA gene transcription.

Yuki Katayama - One of the best experts on this subject based on the ideXlab platform.

  • genetic organization of the chromosome region surrounding meca in clinical staphylococcal strains role of is431 mediated meci deletion in expression of resistance in meca carrying low level Methicillin resistant staphylococcus haemolyticus
    Antimicrobial Agents and Chemotherapy, 2001
    Co-Authors: Yuki Katayama, Keiichi Hiramatsu
    Abstract:

    We report on the structural diversity of mecA gene complexes carried by 38 Methicillin-resistant Staphylococcus aureus and 91 Methicillin-resistant coagulase-negative Staphylococcus strains of seven different species with a special reference to its correlation with phenotypic expression of Methicillin resistance. The most prevalent and widely disseminated mec complex had the structure mecI-mecR1-mecA-IS431R (or IS431mec), designated the class A mecA gene complex. In contrast, in S. haemolyticus, mecA was bracketed by two copies of IS431, forming the structure IS431L-mecA-IS431R. Of the 38 S. haemolyticus strains, 5 had low-level Methicillin resistance (MIC, 1 to 4 mg/liter) and characteristic heterogeneous Methicillin resistance as judged by population analysis. In these five strains, IS431L was located to the left of an intact mecI gene, forming the structure IS431L-class A mecA-gene complex. In other S. haemolyticus strains, IS431L was associated with the deletion of mecI and mecR1, forming the structure IS431L-ΔmecR1-mecA-IS431mec, designated the class C mecA gene complex. Mutants with the class C mecA gene complex were obtained in vitro by selecting strain SH621, containing the IS431L-class A mecA gene complex with low concentrations of Methicillin (1 and 3 mg/liter). The mutants had intermediate level of Methicillin resistance (MIC, 16 to 64 mg/liter). The mecA gene transcription was shown to be derepressed in a representative mutant strain, SH621-37. Our study indicated that the mecI-encoded repressor function is responsible for the low-level Methicillin resistance of some S. haemolyticus clinical strains and that the IS431-mediated mecI gene deletion causes the expression of Methicillin resistance through the derepression of mecA gene transcription.

  • genetic organization of the chromosome region surrounding meca in clinical staphylococcal strains role of is431 mediated meci deletion in expression of resistance in meca carrying low level Methicillin resistant staphylococcus haemolyticus
    Antimicrobial Agents and Chemotherapy, 2001
    Co-Authors: Yuki Katayama, Teruyo Ito, Keiichi Hiramatsu
    Abstract:

    We report on the structural diversity of mecA gene complexes carried by 38 Methicillin-resistant Staphylococcus aureus and 91 Methicillin-resistant coagulase-negative Staphylococcus strains of seven different species with a special reference to its correlation with phenotypic expression of Methicillin resistance. The most prevalent and widely disseminated mec complex had the structure mecI-mecR1-mecA-IS431R (or IS431mec), designated the class A mecA gene complex. In contrast, in S. haemolyticus, mecA was bracketed by two copies of IS431, forming the structure IS431L-mecA-IS431R. Of the 38 S. haemolyticus strains, 5 had low-level Methicillin resistance (MIC, 1 to 4 mg/liter) and characteristic heterogeneous Methicillin resistance as judged by population analysis. In these five strains, IS431L was located to the left of an intact mecI gene, forming the structure IS431L-class A mecA-gene complex. In other S. haemolyticus strains, IS431L was associated with the deletion of mecI and mecR1, forming the structure IS431L-DeltamecR1-mecA-IS431mec, designated the class C mecA gene complex. Mutants with the class C mecA gene complex were obtained in vitro by selecting strain SH621, containing the IS431L-class A mecA gene complex with low concentrations of Methicillin (1 and 3 mg/liter). The mutants had intermediate level of Methicillin resistance (MIC, 16 to 64 mg/liter). The mecA gene transcription was shown to be derepressed in a representative mutant strain, SH621-37. Our study indicated that the mecI-encoded repressor function is responsible for the low-level Methicillin resistance of some S. haemolyticus clinical strains and that the IS431-mediated mecI gene deletion causes the expression of Methicillin resistance through the derepression of mecA gene transcription.

Sheldon L Kaplan - One of the best experts on this subject based on the ideXlab platform.

Stefan Schwarz - One of the best experts on this subject based on the ideXlab platform.

Philip R Cohen - One of the best experts on this subject based on the ideXlab platform.