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Keiichi Hiramatsu

Publications and source records attributed to Keiichi Hiramatsu.

At least 19 recordsLinked to original sources
PubMed2006

Predominance of clones carrying Panton-Valentine leukocidin genes among methicillin-resistant Staphylococcus aureus strains isolated in Japanese hospitals from 1979 to 1985.

We examined 97 strains of methicillin-resistant Staphylococcus aureus (MRSA) isolated between 1979 and 1985, the period of time when the appearance of MRSA strains increased, and we determined that these strains are distinct from the MRSA clones predominating in today's Japanese hospitals. Type IV staphylococcal cassette chromosome mec (SCCmec) strains were the most frequent, comprising 53.6% of all strains, followed by type I (22.7%) and type II (21.6%) SCCmec strains. Among the type IV SCCmec strains, the frequencies of two new subtypes, type IV.3 (IVc) and type IV.4 (IVd), were very high, comprising 38.1 and 10.3% of all strains, respectively. Forty-four of the 97 strains (45.3%) were Panton-Valentine leukocidin (PVL) positive. Among the PVL-positive strains, sequence type 30 (ST30)-SCCmec type IV strains producing type 4 coagulase were the most frequent. This is in striking contrast to the MRSA strains isolated in the 1990s, most of which were ST5-SCCmec type II strains producing type 2 coagulase and positive for the toxic shock syndrome toxin 1 gene. We also identified a new PVL-carrying prophage lysogenized in a type IV.3 SCCmec strain, 81/108. phi108PVL was distinct from the three extant PVL-carrying phages and was presumed to be carried by ST30-type IV.3 SCCmec strains isolated in Japan. These results provide genetic bases for the transition of MRSA clones in Japan that is commonly considered the transition from coagulase type 4 MRSA strains to coagulase type 2 MRSA strains. The results also suggested that MRSA strains that predominated between 1979 and 1985 were generated from PVL-positive methicillin-susceptible S. aureus strains through the integration of SCCmec elements.

Bacterial Toxins↗
PubMed2006

Combination of multiplex PCRs for staphylococcal cassette chromosome mec type assignment: rapid identification system for mec, ccr, and major differences in junkyard regions.

Staphylococcal cassette chromosome mec (SCCmec) typing, in combination with genotyping of the Staphylococcus aureus chromosome, has become essential for defining methicillin-resistant S. aureus (MRSA) clones in epidemiological studies. We have developed a convenient system for SCCmec type assignment. The system consists of six multiplex PCRs (M-PCRs) for identifying the ccr gene complex (ccr), the mec gene complex (mec), and specific structures in the junkyard (J) regions: M-PCR with primer set 1 (M-PCR 1) identified five types of ccr genes; M-PCR 2 identified class A to class C mec; M-PCRs 3 and 4 identified specific open reading frames in the J1 regions of type I and IV and of type II, III, and V SCCmec elements, respectively; M-PCR 5 identified the transposons Tn554 and PsiTn554 integrated into the J2 regions of type II and III SCCmec elements; and M-PCR 6 identified plasmids pT181 and pUB110 integrated into J3 regions. The system was validated with 99 MRSA strains carrying SCCmec elements of different types. The SCCmec types of 93 out of the 99 MRSA strains could be assigned. The SCCmec type assignments were identical to those made with a PCR system that uses numerous primer pairs to identify genes or gene alleles. Our system of six M-PCRs is thus a convenient and reliable method for typing SCCmec elements.

Anti-Bacterial Agents↗
PubMed2006

Prophages of Staphylococcus aureus Newman and their contribution to virulence.

Four prophages (phiNM1-4) were identified in the genome of Staphylococcus aureus Newman, a human clinical isolate. phiNM1, phiNM2 and phiNM4, members of the siphoviridae family, insert at different sites (poiA, downstream of isdB and geh) in the staphylococcal chromosome. phiNM3, a beta-haemolysin (hlb) converting phage, encodes modulators of innate immune responses (sea, sak, chp and scn) in addition to other virulence genes. Replication of phiNM1, phiNM2 and phiNM4 occurs in culture and during animal infection, whereas phiNM3 prophage replication was not observed. Prophages were excised from the chromosome and S. aureus variants lacking phiNM3 or phiNM1, phiNM2 and phiNM4 displayed organ specific virulence defects in a murine model of abscess formation. S. aureus Newman lacking all four prophages was unable to cause disease, thereby revealing essential contributions of prophages to the pathogenesis of staphylococcal infections.

Animals↗
PubMed2006

Novel mechanism of antibiotic resistance originating in vancomycin-intermediate Staphylococcus aureus.

As an aggressive pathogen, Staphylococcus aureus poses a significant public health threat and is becoming increasingly resistant to currently available antibiotics, including vancomycin, the drug of last resort for gram-positive bacterial infections. S. aureus with intermediate levels of resistance to vancomycin (vancomycin-intermediate S. aureus [VISA]) was first identified in 1996. The resistance mechanism of VISA, however, has not yet been clarified. We have previously shown that cell wall thickening is a common feature of VISA, and we have proposed that a thickened cell wall is a phenotypic determinant for vancomycin resistance in VISA (L. Cui, X. Ma, K. Sato, et al., J. Clin. Microbiol. 41:5-14, 2003). Here we show the occurrence of an anomalous diffusion of vancomycin through the VISA cell wall, which is caused by clogging of the cell wall with vancomycin itself. A series of experiments demonstrates that the thickened cell wall of VISA could protect ongoing peptidoglycan biosynthesis in the cytoplasmic membrane from vancomycin inhibition, allowing the cells to continue producing nascent cell wall peptidoglycan and thus making the cells resistant to vancomycin. We conclude that the cooperative effect of the clogging and cell wall thickening enables VISA to prevent vancomycin from reaching its true target in the cytoplasmic membrane, exhibiting a new class of antibiotic resistance in gram-positive pathogens.

Cell Wall↗
PubMed2006

Staphylococcal cassette chromosome mec (SCCmec) typing of methicillin-resistant Staphylococcus aureus strains isolated in 11 Asian countries: a proposal for a new nomenclature for SCCmec elements.

A description of staphylococcal cassette chromosome mec (SCCmec) elements carried by 615 methicillin-resistant Staphylococcus aureus (MRSA) strains isolated in 11 Asian countries is reported, and a novel nomenclatural system based on their structures is proposed. The 615 strains were classified as type 3A (370 strains), type 2A (207 strains), type 2B (32 strains), type 1B (1 strain), and nontypeable (5 strains). The previously reported type III SCCmec (DDBJ/EMBL/GenBank accession no. AB037671) carried by the MRSA strain 85/2082 was ascertained to be composed of two SCC elements, type 3A SCCmec and SCCmercury. PCR analysis indicated that 310 of 370 type 3A SCCmec strains carried both SCC elements. These strains were prevalent in eight countries: Thailand, Sri Lanka, Indonesia, Vietnam, Philippines, Saudi Arabia, India, and Singapore. The remaining 60 type 3A SCCmec strains differed with respect to the left extremity polymorphism or to the presence of ccrC. Among these, two were identified as carrying only type 3A SCCmec elements, but their left extremities differed. Type 2A SCCmec strains predominated in Korea and Japan, although the frequency of the presence of ant(4')-1 gene downstream of mecA varied (53% for Korean strains; 93% for Japanese strains). Various SCCmec elements were identified in the tested strains, and limited numbers were identified by their multilocus sequence typing genotypes. These data suggest that numerous MRSA clones are disseminated in Asian hospitals, and these consist of minor clones that are presumed to have arisen locally and major clones that are presumed to have been introduced from other countries.

Asia↗
PubMed2006

Correlation between Reduced Daptomycin Susceptibility and Vancomycin Resistance in Vancomycin-Intermediate Staphylococcus aureus.

We present here findings of a strong positive correlation between reduced daptomycin susceptibility and vancomycin resistance in vancomycin-intermediate Staphylococcus aureus (VISA). This correlation is related to cell wall thickening, suggesting that, similar to the case with vancomycin resistance in VISA, the physical barrier of a thickened cell wall may contribute to daptomycin resistance in S. aureus.

Anti-Bacterial Agents↗
PubMed2005

Genetic differentiation of methicillin-resistant Staphylococcus aureus strains from Korea and Japan.

In this study, we evaluated genetic differentiation between methicillin-resistant Staphylococcus aureus (MRSA) strains from Korea and Japan. Seventy-five MRSA strains, including 25 h VISA strains, were analyzed by molecular typing methods, including multilocus sequence typing (MLST), SCC mec typing, and spa typing. The most prevalent genotype of MRSA strains, in both Korea and Japan, was ST 5-MRSA-II with the DMGMK spa motif, characteristic of the New York/Japan MRSA clone. In spite of these common features in MRSA strains from Korea and Japan, we also observed some genotypic divergence in MRSA from the two countries. Several spa types might be differentiated from a prevalent prototype (TJMBMDMGMK) that is shared by the two countries, revealing a unique geographic distribution. SCC mec type II lacking pUB110, designated type IIA, was found more frequently in Korea than in Japan. The rate of gentamicin resistance was also dramatically different between the two countries: 87.2% (Korea) vs. 28.6% (Japan). These preliminary findings suggested that MRSA strains from Korea and Japan might have originated from a common ancestor, but then clearly differentiated according to locality. A further comprehensive study should be performed to document the hypotheses from this study.

Bacterial Typing Techniques↗
PubMed2005

Susceptibilities to antiseptic agents and distribution of antiseptic-resistance genes qacA/B and smr of methicillin-resistant Staphylococcus aureus isolated in Asia during 1998 and 1999.

Many antiseptic agents are used in hygienic handwashes in the prevention of nosocomial infections by methicillin-resistant Staphylococcus aureus (MRSA). The plasmid-borne genes qacA/B and smr confer resistance to cationic antiseptic agents in S. aureus. In this study, the susceptibilities for dyes and antiseptic agents (e.g. acriflavine, acrinol, benzalkonium chloride, benzethonium chloride, chlorhexidine digluconate and alkyldiaminoethylglycine hydrochloride) of 894 isolates of MRSA collected from 11 Asian countries (South Korea, China, the Philippines, Singapore, Vietnam, Thailand, Indonesia, India, Sri Lanka, Saudi Arabia and Japan) between 1998 and 1999 were examined. In addition, the distributions of the antiseptic-resistance genes qacA/B and smr were studied by PCR. Among the Asian MRSA isolates 57.7% (516/894) were acriflavine-resistant. The smr gene was detected in 31.6% (12/38) of MRSA isolates from India but only in 1.9% (16/856) of all the isolates from other Asian countries. MRSA with qacA/B comprised 41.6% (372/894) of the isolates across Asia. In addition, PFGE was performed to type the MRSA and grouped the tested 30 MRSA isolates with qacA/B into 21 PFGE types. The results indicated that qacA/B is functionally the most important gene mediating antiseptic resistance in the MRSA strains of Asia and that a specific MRSA with qacA/B was not prevalent in Asia but qacA/B were widely spread among MRSA of Asia, while the geographical distribution of smr is more limited.

Acriflavine↗
PubMed2005

DNA microarray-based identification of genes associated with glycopeptide resistance in Staphylococcus aureus.

Six pairs of transcription profiles between glycopeptide-intermediate S. aureus (GISA [or vancomycin-intermediate S. aureus; VISA]) and glycopeptide-susceptible S. aureus (vancomycin-susceptible S. aureus [VSSA], including glycopeptide-susceptible isogenic mutants from VISA) strains were compared using a microarray. Ninety-two open reading frames which were or tended to be increased in transcription in VISA in at least five out of six array combination pairs were evaluated for their effects on glycopeptide susceptibility by introducing these genes one by one into VSSA strain N315 to construct an overexpression library. By screening the library, 17 genes including 8 novel genes were identified as associated with glycopeptide resistance since their experimental overexpression reduced vancomycin and/or teicoplanin susceptibility of N315. The raised MICs of vancomycin and teicoplanin were 1.25 to 3.0 and 1.5 to 6.0 mg/liter, respectively, as compared to 1.0 mg/liter of N315. Three of these genes, namely graF, msrA2, and mgrA, also raised the oxacillin MIC from 8.0 mg/liter for N315 to 64 to approximately 128 mg/liter when they were overexpressed in N315. Their contribution to vancomycin and beta-lactam resistance was further supported by gene knockout and trans-complementation assay. By using a plasmid-based promoter-green fluorescent protein gene (gfp) transcriptional fusion system, graF promoter-activated cells were purified, and subsequent susceptibility tests and Northern blot analysis demonstrated that the cells with up-regulated activity of graF promoter showed reduced susceptibility to vancomycin, teicoplanin, and oxacillin. In addition, cell morphology studies showed that graF and msrA2 overexpression increased cell wall thickness of N315 by factors of 23.91 and 22.27%, respectively, accompanied by glycopeptide MIC increments of 3- to 6-fold, when they were overexpressed in N315. Moreover, extended experiments and analyses indicate that many of the genes identified above are related to the cell wall biosynthetic pathway, including active nutrient transport systems. We propose that the genes which raise glycopeptide resistance in S. aureus function toward altering the cell wall metabolic pathway.

Anti-Bacterial Agents↗
PubMed2005

Whole-genome sequencing of staphylococcus haemolyticus uncovers the extreme plasticity of its genome and the evolution of human-colonizing staphylococcal species.

Staphylococcus haemolyticus is an opportunistic bacterial pathogen that colonizes human skin and is remarkable for its highly antibiotic-resistant phenotype. We determined the complete genome sequence of S.haemolyticus to better understand its pathogenicity and evolutionary relatedness to the other staphylococcal species. A large proportion of the open reading frames in the genomes of S.haemolyticus, Staphylococcus aureus, and Staphylococcus epidermidis were conserved in their sequence and order on the chromosome. We identified a region of the bacterial chromosome just downstream of the origin of replication that showed little homology among the species but was conserved among strains within a species. This novel region, designated the "oriC environ," likely contributes to the evolution and differentiation of the staphylococcal species, since it was enriched for species-specific nonessential genes that contribute to the biological features of each staphylococcal species. A comparative analysis of the genomes of S.haemolyticus, S.aureus, and S.epidermidis elucidated differences in their biological and genetic characteristics and pathogenic potentials. We identified as many as 82 insertion sequences in the S.haemolyticus chromosome that probably mediated frequent genomic rearrangements, resulting in phenotypic diversification of the strain. Such rearrangements could have brought genomic plasticity to this species and contributed to its acquisition of antibiotic resistance.

Biological Evolution↗
PubMed2005

Dissemination of methicillin-resistant staphylococci among healthy Japanese children.

Methicillin-resistant Staphylococcus aureus (MRSA), regarded as a tenacious pathogen in the hospital, has recently become increasingly prevalent as a community pathogen. We evaluated the prevalence and characteristics of methicillin-resistant staphylococci in the Japanese community by testing nasal samples of 818 children of five day care centers and two kindergartens in three districts. We found that methicillin-resistant staphylococci are already prevalent among healthy children. Among 818 children, 35 children (4.3%) carried MRSA and 231 children (28.2%) carried methicillin-resistant coagulase-negative staphylococci (MRC-NS). The types of staphylococcal cassette chromosome mec (SCCmec) found among 44 MRSA isolates were as follows: type IIa, 11 isolates; type IIb, 19 isolates; and type IV, 14 isolates. The type IIb SCCmec element was a new SCCmec element found in this study. Eleven (25%) strains which belonged to clonal complex 5 (CC5) carried type IIa SCCmec, and they produced type 2 coagulase and toxic shock syndrome toxin 1. They were indistinguishable from health care-associated MRSA (H-MRSA) strains in Japan, represented by strain N315. On the other hand, 33 (75%) strains, most of which belonged to CC78 or CC91, carried small SCCmec elements, such as type IIb or type IV, and they produced type 1 or type 3 coagulase and exfoliative toxin. The data indicated that MRSA clones distinct from H-MRSA have disseminated in healthy children. The fact that MRC-NS strains were prevalent in the community suggested that they might serve as a reservoir for the SCCmec element carried by MRSA strains disseminated in the community.

Bacterial Proteins↗
PubMed2005

Antibacterial activity of dipropofol and related compounds.

Phenolic compounds, in general, exhibit antioxidant and antibacterial activities. We studied antimicrobial activity of the phenolic antioxidants, propofol (2,6-diisopropylphenol), tocopherol, eugenol, butylated hydroxyanisole (BHA), and several of their dimer compounds. Dipropofol (dimer of 2,6-diisopropylphenol) showed strong antibacterial activity against gram-positive strains including methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococci (VRE), while propofol and other monomeric and dimeric phenols having methyl or tert-butyl groups showed no remarkable activity. The results indicated that the dimeric structure of 2,6-diisopropylphenol moiety may play an important role in the antibacterial activity.

Anti-Bacterial Agents↗
PubMed2005

Community-acquired methicillin-resistant Staphylococcus aureus, Uruguay.

A novel, methicillin-resistant [corrected] Staphylococcus aureus clone (Uruguay clone) with a non-multidrug-resistant phenotype caused a large outbreak, including 7 deaths, in Montevideo, Uruguay. The clone was distinct from the highly virulent community clone represented by strain MW2, although both clones carried Panton-Valentine leukocidin gene and cna gene.

Adhesins, Bacterial↗
PubMed2004

Genetic characterization of methicillin-resistant Staphylococcus aureus.

The genome structure of Staphylococcus aureus is analyzed. The genome is composed of two domains. The first domain, descendent from an ancestral bacterial species, contains house-keeping genes that showed highest homology to those of Bacillus species. The second domain contained the genes responsible for virulence and drug-resistance in human infection that seems to have been acquired from other bacterial species via lateral gene transfer. The latter domain constitutes the genetic information that makes S. aureus a notorious hospital pathogen.

Biological Evolution↗