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ABSTRACT: We have developed a modified cyclodextrin solid (MCS) medium using the selective antibiotic cefdinir. MCS medium exhibited higher sensitivity (95.6%; any culture-positive sample as reference) and greater inhibition of nasopharyngeal flora than did Bordet-Gengou agar (65.2%, P = 0.009) or cyclodextrin solid medium (39.1%, P < 0.001).
Journal of clinical microbiology 10/2009; 47(12):4164-7. · 4.16 Impact Factor
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ABSTRACT: Panton-Valentine leukocidin (PVL) has long been considered a critical toxin in severe Staphylococcus aureus infection. PVL presumably breaches the body's defense system by lysing human polymorphonuclear cells (PMNs). Recently, however, bioactive peptides--phenol-soluble modulins (PSMs)--have been proposed as the main player in the lysis of PMNs, rather than PVL. This study aimed to resolve uncertainty concerning the cause of the lysis of human PMNs by using recombinant PVL toxins and PVL-neutralizing monoclonal antibodies. The recombinant PVL toxins showed strong lytic activity against human but not murine neutrophils. Moreover, the lytic activity of culture supernatants of strains USA400 MW2 and USA300 FPR3757 were completely neutralized by anti-PVL monoclonal antibodies. In contrast, phenol-soluble modulin alpha 3--the most potent PSM peptide--failed to lyse human PMNs at the concentrations contained in the culture supernatants. Phenol-soluble modulin alpha 3 did, however, enhance PVL-mediated lysis of human PMNs.
The Journal of Infectious Diseases 10/2009; 200(5):715-23. · 6.41 Impact Factor
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ABSTRACT: Methicillin-resistant Staphylococcus aureus (MRSA) arises when methicillin-susceptible S. aureus (MSSA) acquires the staphylococcal cassette chromosome mec (SCCmec). Most pvl-positive MRSA in Taiwan belong to ST59 lineage and carry SCCmec V. The genetic profiles of 51 MSSA were compared with those of 80 MRSA from the same hospitals. Nine pvl-positive MSSA (oxacillin MIC < or = 2 microg/mL) shared >80% similarity in pulsed field gel electrophoresis pattern with 17 pvl-positive SCCmec V MRSA. Further investigation found that 5 of these 9 isolates were MRSA by cefoxitin and carried SCCmec V. All 26 pvl-positive isolates had very similar genetic profile (ST59, protein A clonal complex [spa-CC] c2:441/437, and agr group I). The success of the ST59:SCCmec V MRSA may be due in part to its heterogeneous and borderline resistance to methicillin, which may be missed by testing only oxacillin, with subsequent exposure to beta-lactams causing the emergence of more resistant subpopulations.
Diagnostic microbiology and infectious disease 09/2009; 65(4):351-7. · 2.45 Impact Factor
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ABSTRACT: Endotoxin shock is a severe systemic inflammatory response that is caused by the augmented production and release of septic mediators. Among them, inflammatory cytokines such as tumor necrosis factor-alpha, IL-1beta and IL-6 play a pivotal role. In addition, anandamide, an endogenous cannabinoid and high-mobility group box-1 (HMGB1), a non-histone chromosomal protein has recently been recognized as members of septic mediators. We previously reported that cationic antibacterial polypeptide of 11-kDa (CAP11), an antimicrobial cathelicidin peptide (originally isolated from guinea pig neutrophils), potently neutralizes the biological activity of LPS and protects mice from lethal endotoxin shock. In this study, to clarify the protective mechanism of CAP11 against endotoxin shock, we evaluated the effects of CAP11 on the production and release of septic mediators in vitro and in vivo using a murine macrophage cell line RAW264.7 and a D-galactosamine-sensitized murine endotoxin shock model. LPS stimulation induced the production of inflammatory cytokines and anandamide and release of HMGB1 from RAW264.7 cells. Importantly, CAP11 suppressed the LPS-induced production and release of these mediators by RAW264.7 cells. Moreover, LPS administration enhanced the serum levels of HMGB1, anandamide and inflammatory cytokines in the endotoxin shock model. Of note, CAP11 suppressed the LPS-induced increase of these mediators in sera, and LPS binding to CD14-positive cells (peritoneal macrophages), accompanied with the increase of survival rates. Together these observations suggest that the protective action of CAP11 on endotoxin shock may be explained by its suppressive effect on the production and release of septic mediators by CD14-positive cells possibly via the inhibition of LPS binding to the targets.
International Immunology 07/2009; 21(8):905-12. · 3.41 Impact Factor
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ABSTRACT: Recently, strains of methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin (VCM) have been clinically isolated. The antibacterial activity of a new drug, linezolid (LZD), in such a strain was evaluated by measuring bacterial metabolic activity. A total of 73 MRSA strains having various susceptibilities to VCM were subjected to a novel and highly sensitive chemiluminescence-based assay. LZD MIC in the tested strains, measured by the microbroth dilution method, was within the range 1-4 mg/l (mostly </=2 mg/l), except for one LZD-resistant strain (NRS127; MIC=7 mg/l), and showed no correlation with VCM resistance. The chemiluminescence assay demonstrated that bacterial metabolic activity was strongly suppressed with increasing LZD concentration. The chemiluminescence intensity curve had a low baseline activity without tailing in most strains. The present results suggest that LZD has strong antibacterial activity against MRSA strain, and would be effective for treatment of infections that are poorly responsive to VCM. The chemiluminescence assay facilitated sensitive and discriminative susceptibility testing within a relatively short time.
Journal of Microbiology and Biotechnology 07/2009; 19(7):734-42. · 1.38 Impact Factor
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ABSTRACT: We identified two novel staphylococcal cassette chromosome mec (SCCmec) elements in sequence type 8 methicillin-resistant Staphylococcus aureus strains isolated in Japan: type II.5 SCCmec, whose J1 region was highly homologous to that of type I.2 SCCmec of strain PL72 (previously isolated in Poland), and its J1 region variant caused by the deletion/insertion of putative conjugative transposon Tn6012, identified in four S. aureus genomes.
Antimicrobial Agents and Chemotherapy 05/2009; 53(6):2616-9. · 4.84 Impact Factor
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ABSTRACT: We screened 533 and 361 methicillin (meticillin)-resistant Staphylococcus aureus strains isolated in a university hospital in 2002 and 2003 and in 2006 and 2007, respectively, and identified 4 (0.8%) of the strains in the first group and 8 (2.2%) of the strains in second group as heterogeneous vancomycin-resistant S. aureus (heterogeneous VISA) strains and 3 (0.8%) of the strains in the second group as VISA strains. This is the first report of VISA strains isolated from patients in Thailand.
Journal of clinical microbiology 05/2009; 47(7):2311-6. · 4.16 Impact Factor
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ABSTRACT: Six Bordetella pertussis strains isolated from children in Japan from 2004 to 2006 showed high-level resistance to nalidixic acid (NAL; MIC, >256 microg/ml) and decreased susceptibilities to fluoroquinolones. All of the NAL-resistant strains had the same D87G mutation in gyrA.
Antimicrobial Agents and Chemotherapy 05/2009; 53(7):3147-9. · 4.84 Impact Factor
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ABSTRACT: To identify risk factors associated with nosocomial bloodstream infections caused by multiple clones of the staphylococcal cassette chromosome mec (SCCmec) type IV strain of methicillin-resistant Staphylococcus aureus (MRSA).
An unmatched case-control study (at a ratio of 1:2) performed during the period from October 2002 through September 2003.
A 2,000-bed tertiary care teaching hospital affiliated with the University of São Paulo in São Paulo, Brazil.
Case patients (n=30) were defined either as patients who had a bloodstream infection due to SCCmec type IV MRSA diagnosed at least 48 hours after hospital admission or as neonates with the infection who were born in the hospital. Control patients (n=60) were defined as patients with SCCmec type III MRSA infection diagnosed at least 48 hours after hospital admission. Genes encoding virulence factors were studied in the isolates recovered from case patients, and molecular typing of the SCCmec type IV MRSA isolates was also done by pulsed-field gel electrophoresis and multilocus sequence typing.
In multivariate analysis, the following 3 variables were significantly associated with having a nosocomial bloodstream infection caused by SCCmec type IV strains of MRSA: an age of less than 1 year, less frequent use of a central venous catheter (odds ratio [OR], 0.07 [95% confidence interval {CI}, 0.02-0.28]; p= .025), and female sex. A second analysis was performed that excluded the case and control patients from the neonatal unit, and, in multivariate analysis, the following variables were significantly associated with having a nosocomial bloodstream infection caused by SCCmec type IV strains of MRSA: less frequent use of a central venous catheter (OR, 0.12 [95% CI, 0.03-0.55]; p= .007), lower Acute Physiology and Chronic Health Evaluation II score on admission (OR, 0.14 [95% CI, 0.03-0.61]; p= .009), less frequent surgery (OR, 0.21 [95% CI, 0.06-0.83]; p= .025), and female sex (OR, 5.70 [95% CI, 1.32-24.66]; p= .020). Of the 29 SCCmec type IV MRSA isolates recovered from case patients, none contained the Panton-Valentine leukocidin, gamma-hemolysin, enterotoxin B or C, or toxic shock syndrome toxin-1. All of the isolates contained genes for the LukE-LukD leukocidin and alpha-hemolysin. Genes for enterotoxin A were present in 1 isolate, and genes for beta-hemolysin were present in 3 isolates.
"Classical" risk factors do not apply to patients infected with the SCCmec type IV strain of MRSA, which is an important cause of nosocomial bacteremia. This strain infects a patient population that is less ill and has had less frequent invasive procedures than a patient population infected with the multidrug-resistant strain of SCCmec type III MRSA. We found that virulence factors were rare and that Panton-Valentine leukocidin was absent. There were multiple clones of the SCCmec type IV strain in our hospital. Children under 1 year of age were at a higher risk. There was a predominant clone (sequence type 5) in this patient population.
Infection Control and Hospital Epidemiology 03/2009; 30(2):139-45. · 3.67 Impact Factor
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ABSTRACT: We describe here the genetic analysis of a vancomycin-susceptible Staphylococcus aureus (VSSA) strain, Mu50Omega, a strain related to vancomycin-intermediate S. aureus (VISA) strain Mu50. Using a combination of Mu50Omega whole-genome sequencing and genome engineering, we observed a stepwise evolution of vancomycin resistance from VSSA to VISA after the mutated vraS and graR genes of Mu50 were engineered into Mu50Omega.
Antimicrobial Agents and Chemotherapy 02/2009; 53(3):1231-4. · 4.84 Impact Factor
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ABSTRACT: We identified a novel type-III staphylococcal cassette chromosome mec (SCCmec) element carried by eight methicillin-resistant Staphylococcus aureus (MRSA) strains from different wards and patients in an Indian hospital. Although the pulsed-field gel electrophoresis pattern and spa types of eight strains were identical and clonally related to other nosocomial Indian isolates that belonged to sequence type (ST) 239 and spa type t037, the minimum inhibitory concentration (MIC) of these eight variants was noticeably low compared with the typical type-III isolates from the same hospital, and we were unable to identify ccrC and hsdR by multiplex PCR, although mer operon and transposases A, B, and C of Tn554 were amplified. By amplifying the entire SCCmec region by long-range PCR and determining parts of the nucleotide sequences of one isolate (V14), we found that the strain carried a novel SCCmec element containing a 422 bp sequence, which is highly homologous to that identified in strain CCR1-9583, mer operon and plasmid pT181 integrated in tandem via IS431 in the J3 region. It also carried a cassette chromosome, previously reported to be an SCC-like element, downstream of type-III SCCmec. Because PCR amplification of representative genes showed that these eight strains carried the same genetic elements, they belong to a novel MRSA clone that differs from most nosocomial clones carrying type-III SCCmec and SCCmercury, despite belonging to the ST239 genotype.
FEMS Microbiology Letters 02/2009; 292(1):141-8. · 2.04 Impact Factor
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ABSTRACT: The production of staphylocoagulase (SC) causing the plasma coagulation is one of the important characteristics of Staphylococcus aureus. Although SCs have been classified into 10 serotypes based on the differences in the antigenicity, genetic bases for their diversities and relatedness to chromosome types are poorly understood.
We compared the nucleotide sequences of 105 SC genes (coa), 59 of which were determined in this study. D1 regions, which contain prothrombin-activating and -binding domains and are presumed to be the binding site of each type-specific antiserum, were classified into twelve clusters having more than 90% nucleotide identities, resulting to create two novel SC types, XI and XII, in addition to extant 10 types. Nine of the twelve SC types were further subdivided into subtypes based on the differences of the D2 or the central regions. The phylogenetical relations of the D1 regions did not correlate exactly with either one of agr types and multilocus sequence types (STs). In addition, genetic analysis showed that recombination events have occurred in and around coa. So far tested, STs of 126 S. aureus strains correspond to the combination of SC type and agr type except for the cases of CC1 and CC8, which contained two and three different SC types, respectively.
The data suggested that the evolution of coa was not monophyletic in the species. Chromosomal recombination had occurred at coa and agr loci, resulting in the carriage of the combinations of allotypically different important virulence determinants in staphylococcal chromosome.
PLoS ONE 02/2009; 4(5):e5714. · 4.09 Impact Factor
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ABSTRACT: Vancomycin (VAN)-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) isolates are considered to have emerged from VAN-susceptible S. aureus (VSSA) by spontaneous mutation during VAN exposure. We previously reported that laboratory mutant H14, obtained from VSSA strain IP by exposure to imipenem (IPM), showed overexpression of the vraSR two-component system and a typical hVISA phenotype. In the present study, to elucidate the mechanism of VSSA conversion to hVISA, we further characterized strain H14 by determining its whole-genome sequence, morphology, cell wall synthetic activity, and gene expression. Genome sequencing revealed that H14 harbored a mutated vraS (designated vraS H14) that caused an amino acid substitution (S 329 3L). This mutation is different from the VraS mutation (N 5 3I) identified in repre-sentative clinical hVISA strain Mu3. However, H14 exhibited a phenotype similar to that of Mu3, including heterogeneous resistance to VAN, enhanced cell wall synthetic activity, and vraSR overexpression. Replacement of the vraS gene of IP with the mutated vraS H14 gene confirmed that the S 329 3L substitution was responsible for both the upregulation of vraSR and conversion to the hVISA phenotype. This conversion was also achieved by using the vraS gene of Mu3, which carries a mutation (N 5 3I), but not with the native vraS gene of strain N315. Finally, we carried out a study to analyze the appearance of hVISA from VSSA by exposure of IP to selective concentrations of VAN and beta-lactam antibiotics. A total of 8 and 5 hVISA isolates were detected among 50 isolates selected with VAN and IPM, respectively. Among the 13 hVISA mutants, mutation in vraSR was detected only in mutant strain H14, suggesting that additional mutational mechanisms can be responsible for evolution to the hVISA phenotype. We conclude that exposure not only to VAN but also to beta-lactams may select for reduced glycopeptide susceptibility in S. aureus. Methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) is a major cause of serious nosocomial infections, and the emer-gence of virulent MRSA strains in the community is of partic-ular concern (6). Vancomycin (VAN) still serves as the main therapeutic agent for infections caused by multiresistant MRSA strains (17). However, MRSA strains with various de-grees of reduced susceptibility to glycopeptides, vancomycin-intermediate S. aureus (VISA) and heterogeneous VISA (hVISA) strains, have emerged among multidrug-resistant MRSA clinical strains (9, 16). Recently, we identified several genes that are overexpressed in VISA strain Mu50 and hVISA Mu3 compared to their levels of expression in their isogenic VAN-susceptible S. aureus (VSSA) strain, strain Mu50 (13); and among these, we found the overexpression of the vraSR two-component system (TCS), an upregulator of the S. aureus cell wall biosynthesis pathway (12, 13). We also demonstrated that the vraS gene is overex-pressed in IP-H14 (H14), a laboratory-derived hVISA strain obtained by selecting VSSA strain N315IP (IP) with 8 mg/liter of imipenem (IPM) (12) and showed that a single amino acid substitution in VraS was present in H14, Mu3, and Mu50 (10a). In the study described here, we further characterized hVISA strain H14, investigated the role of the vraS mutation on the phenotype of H14, and evaluated the rates of selection of hVISA from VSSA IP following exposure to VAN and beta-lactam antibiotics.
Antimicrobial Agents and Chemotherapy 01/2009; 53(8):3190--3196. · 4.84 Impact Factor
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ABSTRACT: We isolated the methicillin-resistant Macrococcus caseolyticus strain JCSC5402 from animal meat in a supermarket and determined its whole-genome nucleotide sequence. This is the first report on the genome analysis of a macrococcal species that is evolutionarily closely related to the human pathogens Staphylococcus aureus and Bacillus anthracis. The essential biological pathways of M. caseolyticus are similar to those of staphylococci. However, the species has a small chromosome (2.1 MB) and lacks many sugar and amino acid metabolism pathways and a plethora of virulence genes that are present in S. aureus. On the other hand, M. caseolyticus possesses a series of oxidative phosphorylation machineries that are closely related to those in the family Bacillaceae. We also discovered a probable primordial form of a Macrococcus methicillin resistance gene complex, mecIRAm, on one of the eight plasmids harbored by the M. caseolyticus strain. This is the first finding of a plasmid-encoding methicillin resistance gene. Macrococcus is considered to reflect the genome of ancestral bacteria before the speciation of staphylococcal species and may be closely associated with the origin of the methicillin resistance gene complex of the notorious human pathogen methicillin-resistant S. aureus.
Journal of bacteriology 01/2009; 191(4):1180-90. · 3.94 Impact Factor
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ABSTRACT: Recent studies have shown a predominance of type IV SCCmec among the methicillin-resistant Staphylococcus aureus (MRSA) isolated in the low endemic areas of Orebro County and the western region of Sweden. However, many of these isolates were not possible to classify as existing subtypes IVa, IVb, IVc or IVd.
We analysed 16 such MRSA isolates by multilocus sequence typing, spa typing, staphylocoagulase (SC) typing and detection of type IVg and IVh SCCmec. MRSA that remained as unknown type IV SCCmec were investigated by long-range PCR covering the J1 region; however, only two isolates were possible to amplify by PCR. The nucleotide sequences of the entire SCCmec of these two MRSA were determined. In addition, isolates that had unknown SC types were investigated by nucleotide sequencing of the coa genes.
Five of 16 isolates were classified as type IVg SCCmec, and four isolates had type IVh SCCmec. Two subtypes of type IV SCCmec shared J1 regions previously identified in other types of SCCmec, types I.2 and II.2. The novel elements were designated as type IVi and IVj SCCmec. In addition, the genetic backgrounds of these Swedish MRSA were diverse and constituted at least nine sequence types and eight SC types, including four new types of SC.
Type IV SCCmec is occurring in heterogeneous clones of MRSA in Sweden, and the majority of the type IV SCCmec were identified in community-acquired MRSA. We describe two novel subtypes of type IV SCCmec with common J1 regions shared by other types of SCCmec, which indicate that J1 regions occurred as primordial SCC.
Journal of Antimicrobial Chemotherapy 12/2008; 63(1):32-41. · 5.07 Impact Factor
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Tengku Zetty,
Maztura Tengku Jamaluddin,
Kyoko Kuwahara-Arai,
Ken Hisata,
Masahiko Terasawa,
Longzhu Cui,
Tadashi Baba,
Chie Sotozono,
Shigeru Kinoshita,
Teruyo Ito, Keiichi Hiramatsu
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ABSTRACT: For the past few years, we have been observing the dissemination of methicillin-resistant staphylococci in the community. From 2001 to 2003, an evaluation of nasal samples from 1,285 children in five day-care centers and two kindergartens in three districts in Japan revealed that methicillin-resistant coagulase-negative staphylo-cocci (MRC-NS) have been widely disseminated in the Japanese community. Their prevalence is much greater than community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). Forty-nine children (3.81%) were colonized with MRSA, whereas 390 children (30.35%) were colonized with MRC-NS. These MRC-NS strains predominantly harbored a pair of cassette chromosome recombinase types A2 and B2 (ccrAB2). Of these, 40.8% harbored type IVa staphylococcal cassette chromosome mec (SCCmec) elements, a distinct/ characteristic type of SCCmec in pandemic clones of CA-MRSA. Interestingly, there was also a high frequency of nontypeable strains which possessed atypical structures compared to previous SCCmec types. Among the MRC-NS, the majority of strains (63.59%) were methicillin-resistant Staphylococcus epidermidis (MRSE). Their genotypes, as judged from pulsed-field gel electrophoresis (PFGE), were highly diverse. They were so diverse that there was no sign of an immediate transmission of any MRSE clone among children in the same institutions. In a previous report, we expounded that a few CA-MRSA clones with distinct SCCmec types were disseminated among children in the same institutions. Au contraire, with the case of CA-MRSE, there was no single genotype of CA-MRSE disseminated among children even in the same institution or class. Staphylococcus aureus is not a stranger to pediatric patients; its ability to cause a wide spectrum of infections among this vulnerable group warrants its distribution to be observed pe-riodically, more than ever with the emergence of methicillin-resistant Staphylococcus aureus (MRSA) in the community in the past decade (10, 11, 21, 23). In the past, MRSA was deemed to be a nosocomial pathogen and infrequently isolated in healthy individuals in the community. MRSA infections account for increased cost and mortality both locally and worldwide. Significant advances in MRSA epidemiology have been made since the discovery of the genetic mechanism by which each MRSA clone is generated, namely the integration of the staphylococcal cassette chromosome mec (SCCmec) el-ement into the S. aureus chromosome (8, 9). For many years, it has been the focus of clinicians and researchers alike in determining and understanding the route of transmission of this clinically important mobile genetic element. However, the origin of SCCmec remains uncertain. There is no allelic equiv-alent of mecA in methicillin-susceptible Staphylococcus aureus. The common thought is that MRSA acquired SCCmec from other staphylococci species, most presumably from its coagu-lase-negative counterparts (1, 7, 13, 14, 16, 26). Coagulase-negative staphylococci (C-NS) are commensal bacteria of human skin and nasal and oral mucosa. In the advent of increased invasive interventions and treatments, C-NS have been frequently detected as a cause of opportunis-tic infections (15). They are difficult to eradicate, as they pos-sess the capacity to form biofilms on indwelling devices (6, 22, 26). Furthermore, medical and health-care workers pose as reservoirs of infection for susceptible patients (2). According to the National Nosocomial Infectious Surveillance of the United States of America, the rates of methicillin resistance have increased in the last two decades (17). Worldwide surveys revealed that 60 to 85% of clinical strains are resistant to methicillin (4, 17, 19) The detection of MRC-NS in health-care settings has never been more important due to the narrow therapeutic approaches available. Most alarmingly, the inci-dence of methicillin-resistant C-NS (MRC-NS) has also am-plified in individuals without established risk factors in the community (4, 10, 23). For the past few years, we have been trying to comprehend the mode of dissemination of SCCmec among staphylococci in the community. Interestingly, we dis-covered that MRC-NS strains have been steadily disseminated in the Japanese community and are ominously more prevalent than CA-MRSA (K. Kuwahara-Arai, unpublished data) (10). These strains predominantly harbored type IV SCCmec ele-ments, similarly to CA-MRSA strains disseminated in the world (5, 18, 21). Most of the studies pertaining to community-acquired staph-ylococci mainly concentrated on S. aureus. Our literature re-view also revealed that a wide proportion of studies on the
Journal of clinical microbiology 12/2008; 46(11):3778--3783. · 4.16 Impact Factor
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ABSTRACT: For the past few years, we have been observing the dissemination of methicillin-resistant staphylococci in the community. From 2001 to 2003, an evaluation of nasal samples from 1,285 children in five day-care centers and two kindergartens in three districts in Japan revealed that methicillin-resistant coagulase-negative staphylococci (MRC-NS) have been widely disseminated in the Japanese community. Their prevalence is much greater than community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). Forty-nine children (3.81%) were colonized with MRSA, whereas 390 children (30.35%) were colonized with MRC-NS. These MRC-NS strains predominantly harbored a pair of cassette chromosome recombinase types A2 and B2 (ccrAB2). Of these, 40.8% harbored type IVa staphylococcal cassette chromosome mec (SCCmec) elements, a distinct/characteristic type of SCCmec in pandemic clones of CA-MRSA. Interestingly, there was also a high frequency of nontypeable strains which possessed atypical structures compared to previous SCCmec types. Among the MRC-NS, the majority of strains (63.59%) were methicillin-resistant Staphylococcus epidermidis (MRSE). Their genotypes, as judged from pulsed-field gel electrophoresis (PFGE), were highly diverse. They were so diverse that there was no sign of an immediate transmission of any MRSE clone among children in the same institutions. In a previous report, we expounded that a few CA-MRSA clones with distinct SCCmec types were disseminated among children in the same institutions. Au contraire, with the case of CA-MRSE, there was no single genotype of CA-MRSE disseminated among children even in the same institution or class.
Journal of clinical microbiology 11/2008; 46(11):3778-83. · 4.16 Impact Factor
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ABSTRACT: Staphylocoagulases (SCs) have been classified by the differences in antigenicity using a serological method. We have developed a system to classify them based on the nucleotide differences in SC genes (coa). The system was composed of three multiplex PCRs (M-PCRs): M-PCR:A, identifying types III, IV, VII, and VIII; M-PCR:B, identifying types I, II, V, and VI; M-PCR:C, identifying three subtypes of type VI. In this study, we found that coa genes of the serotype VI were not identical, but classified into three subtypes based on the nucleotide differences, especially in D2 and the central region: VIa, the coa gene carried by stp12 from human; and VIb and VIc, the coa genes carried by strains IFH556 and IFH514 isolated from bovine raw milk. The primer pair used in M-PCR:B was designed to identify all three subtypes of type VI coa. The results showed that coa types of 154 out of 155 Staphylococcus aureus strains from various origins assigned by M-PCR:A and B were identical to those obtained by serological methods, leaving a serotype IV strain unclassifiable. All 73 type VI strains were classified into one of three subtypes by M-PCR:C. Furthermore, we found that type VIa and VIb strains carried characteristic pyrogenic toxin superantigen genes, while no toxin genes were identified in type VIc strains, suggesting the correlation between the subtype of type VI coa gene and the carriage of genomic islands. Our results showed that these M-PCRs are convenient methods for SC typing that might be useful for epidemiological studies.
Journal of Microbiological Methods 11/2008; 75(2):312-7. · 2.09 Impact Factor
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ABSTRACT: A new chromosome-carried quinolone resistance gene from Stenotrophomonas maltophilia, Smqnr, was characterized. The gene was present in type strain CCUG 5866 and was also detected in 24 clinical isolates and showed some allelic diversity. The expression of Smqnr in Escherichia coli decreased the susceptibilities of the E. coli isolates to several fluoroquinolones.
Antimicrobial Agents and Chemotherapy 10/2008; 52(10):3823-5. · 4.84 Impact Factor
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ABSTRACT: In order to better understand the mechanism of daptomycin resistance, we generated a daptomycin-nonsusceptible derivative strain, strain 10*3d1 (MIC = 3.0 microg/ml), by in vitro exposure of methicillin-resistant Staphylococcus aureus strain N315DeltaIP (MIC = 0.5 microg/ml) to daptomycin. We also obtained a daptomycin-susceptible phenotypic revertant strain, strain 10*3d1-10 (MIC = 1.0 microg/ml), by passaging 10*3d1 in drug-free medium for 10 days. The resultant triple-isogenic strains were analyzed for their phenotypes and gene expression by microarray analysis. No significant differences in the membrane fluidities of 10*3d1 and 10*3d1-10 compared to the membrane fluidity of N315DeltaIP were observed. Resistant strain 10*3d1 had the highest membrane potential, followed by strains 10*3d1-10 and N315DeltaIP. The vancomycin and teicoplanin MICs also increased. Teichoic acid genes (tagA, tagG), mprF encoding lysyl-phosphatidylglycerol, and cls encoding cardiolipin synthase were downregulated in 10*3d1 and 10*3d1-10. The vraF and vraG genes, which encode ATP binding cassette transporter proteins, were upregulated in 10*3d1. The vraSR two-component regulatory system was upregulated, and electron microscopy revealed that the cell wall of 10*3d1 was significantly thicker than that of the parental strain. Taken together, daptomycin exposure selected a daptomycin-nonsusceptible strain with a phenotype similar to that of heterogeneous vancomycin-intermediate S. aureus and a transcription profile that partially overlapped that of heterogeneous vancomycin-intermediate S. aureus.
Antimicrobial Agents and Chemotherapy 10/2008; 52(12):4289-99. · 4.84 Impact Factor
