Kiyoshi Sato

Sapporo Medical University, Sapporo, Hokkaidō, Japan

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Publications (13)28.5 Total impact

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    ABSTRACT: Serotypeable strains of Haemophilus influenzae, which can cause invasive infections, are found in the respiratory tract at low frequencies. We compared the antibiotic resistance of the typeable and nontypeable strains of H. influenzae in respiratory tract specimens obtained in Japan. We determined the serotypes and the antibiotic susceptibilities of 440 clinical H. influenzae strains isolated from respiratory tract specimens. We also examined the prevalence of genotypes that are associated with beta-lactam resistance. The majority of the strains were nontypeable (421 strains, 95.7%). The remainder belonged to serotypes b (10 strains, 2.3%), e (three strains, 0.7%), or f (six strains, 1.4%). The type b strains exhibited the expression of beta-lactamase and resistance mutations in penicillin-binding protein 3 with significantly higher frequencies than other strains. H. influenzae type b strains, which are associated with meningitis and bacteremia, derived from respiratory tract specimens, shared more beta-lactam-resistant mechanisms than nontypeable and other serotype strains.
    International journal of infectious diseases: IJID: official publication of the International Society for Infectious Diseases 02/2009; 13(5):584-8. · 2.17 Impact Factor
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    ABSTRACT: Recently, the frequency of isolation of beta-lactamase-negative ampicillin resistant (BLNAR) strains of Haemophilus influenzae in Japanese children has been increasing rapidly. Drug resistance in BLNAR strains is associated with mutations of the fts I gene, which encodes penicillin-binding protein 3. In the otolaryngological field, only a few reports have been available concerning fts I gene mutations in BLNAR. We investigated the prevalence of fts I gene mutations, by polymerase chain reaction (PCR) genotyping, in H. influenzae isolates from the upper respiratory tracts of children in the Sapporo district, Japan. When the isolates were classified according to PCR genotyping, 34 (44.2%) of 77 isolates were beta-lactamase-negative ampicillin-sensitive (g-BLNAS), 8 (10.4%) were g-low-BLNAR, 30 (39.0%) were g-high-BLNAR, 2 (2.6%) were beta-lactamase-positive ampicillin-resistant (g-BLPAR), and 3 (3.9%) were beta-lactamase-positive ampicillin/clavulanic acid-resistant (g-high-BLPACR). Mutations in the fts I gene were generally parallel to ampicillin susceptibility, and were frequently observed in children who were 7 years or younger. Of the beta-lactams tested, cefditoren showed the strongest inhibition of H. influenzae isolates, and it inhibited g-BLNAR and g-BLPACR. This study revealed a remarkably high prevalence of fts I gene mutations (g-BLNAR and g-BLPACR) in our district. Furthermore, a regional difference in the prevalence of fts I gene mutations was observed even at the district level.
    Journal of Infection and Chemotherapy 07/2008; 14(3):223-7. · 1.55 Impact Factor
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    ABSTRACT: Any increase in beta-lactam-resistant Haemophilus influenzae is a serious problem in respiratory and otolaryngology medicine. In this study, we examined the antibiotic susceptibility and genotype of 457 clinical Haemophilus influenzae strains isolated in Hokkaido Prefecture, Japan. Strains with beta-lactam-resistant mutations in gene encoding penicillin-binding protein 3 were more frequently found in lower respiratory tract specimens (sputa) than in upper respiratory tract specimens, such as rhinorrhea. The existence of the TEM-1 beta-lactamase gene occurred more frequently in adult patients than in pediatric patients. The results suggest that beta-lactam-resistant or nonsusceptible strains are more prevalent in adult patients with respiratory diseases. We observed only a very few strains which were nonsuscpetible to third-generation cephalosporins (CEPs) and carbapenems. However, 12%-13% of the strains were shown to be resistant to penicillins and second-generation CEPs, and approximately 4% of the strains were shown to be nonsusceptible to fourth-generation CEPs. In addition, we identified tetracycline-resistant (2.8%), chloramphenicol-resistant (0.6%), clarithromycin-resistant (2.6%), and fluoroquinolone-nonsusceptible (approximately 2%) H. influenzae strains.
    Journal of Infection and Chemotherapy 05/2008; 14(2):93-8. · 1.55 Impact Factor
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    ABSTRACT: We screened 457 Haemophilus influenzae strains isolated in Japan during 2002 to 2004 and identified 12 fluoroquinolone-resistant strains (2.6%). The resistant strains were divided into three genotypes (eight, three, and one of each type). These were isolated from patients over 58 years of age. Several fluoroquinolone-resistant clones appeared to have invaded the population of elderly patients in a particular area, Sapporo city.
    Journal of clinical microbiology 02/2008; 46(1):361-5. · 4.16 Impact Factor
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    ABSTRACT: Our previous study demonstrated that the frequency of penicillin-resistant Streptococcus pneumoniae (PRSP) was lower in our district than in districts in other Japanese studies. In this study, we investigated the prevalence of erythromycin resistance. The susceptibility to erythromycin and the distribution of the macrolide-resistance genes, mefA and ermB, were examined in S. pneumoniae isolates from the upper respiratory tracts of children in four cities in the Sapporo district, Hokkaido prefecture, Japan. Of the 156 isolates, 27 (17.3%) were erythromycin-sensitive, 6 (3.9%) were erythromycin-intermediately resistant, and 123 (78.9%) were erythromycin-resistant. Fifty-nine (37.8%) had the mefA gene, 89 (57.1%) had the ermB gene, and 129 (82.7%) had the mefA and/or the ermB gene. The ermB-positive isolates tended to show high resistance to erythromycin. Erythromycin-resistant isolates and the macrolide-resistance genes were often present in infants or younger children. The frequency of erythromycin-resistant isolates in the four cities was very high, ranging from 76.3% to 83. 3%, as high as the national average. Although erythromycin-resistant isolates generally tend to show cross-resistance to penicillin, the frequency of PRSP was very low in this study, as compared with other Japanese studies. Erythromycin resistance was frequently recognized not only in PRSP but also in penicillin-sensitive S. pneumoniae (PSSP) as well. In Japan, erythromycin resistance may have already become widespread, even in local areas where penicillin resistance is not especially prevalent.
    Journal of Infection and Chemotherapy 09/2007; 13(4):219-23. · 1.55 Impact Factor
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    ABSTRACT: Recurrent otitis media are frequently intractable during childhood. It is unclear whether recurrent otitis media is caused by etiological bacteria colonization or by new infections. Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis were isolated from the nasopharynx of 7 otitisprone and 2 non-prone children with recurrent otitis media. Plural bacterial species and strains were found in all children while affected by otitis media. The same strain was repeatedly isolated from all otitisprone children even after administration of antibiotics but was not from the non-prone children. Antibiotic susceptibility did not differ significantly among the same repeatedly isolated strains. This pilot study suggests that the etiological bacteria tend to colonize and is hard to eliminate in otitis-prone children.
    Microbiology and Immunology 02/2007; 51(2):223-30. · 1.55 Impact Factor
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    ABSTRACT: Evaluation of beta-lactam susceptibility and polymerase chain reaction (PCR)-based genotyping of penicillin-binding proteins (PBP) 1A, 2B, and 2X were performed for Streptococcus pneumoniae isolates from children with otolaryngological infectious disease in the Sapporo district, Hokkaido Prefecture, Japan. Of 174 S. pneumoniae isolates, 14 (8%) were penicillin-resistant S. pneumoniae (PRSP), 87 (50%) were penicillin-intermediately-resistant, and 73 (42%) were penicillin-sensitive. Seventy-six (44%) had alterations in all of the three genes examined (pbp1a, pbp2b, and pbp2x), 81 (47%) had alterations in one or two of the genes, and 17 (10%) had no alterations. Isolates with alterations in all three genes showed low susceptibility to penicillin, while, in contrast, isolates with no alteration showed relatively high susceptibility to penicillin. Similar relationships were observed for other beta-lactams. The prevalence of PRSP in our study ranged from 5% to 12.8% (average, 8%), and there was much variation in the prevalence of PBP gene alterations among the cities. The results suggest that local differences in patterns of PBP gene alterations can be observed even at the district level. PCR-based genotyping of PBP genes is rapid, convenient, and useful to investigate genetic susceptibility to beta-lactams. Further, not only nationwide or prefectural surveys but also local surveillance at the district level is important for determining antimicrobial susceptibility status in daily practice.
    Journal of Infection and Chemotherapy 01/2007; 12(6):366-71. · 1.55 Impact Factor
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    ABSTRACT: Recent studies have speculated on the possible role of the mother in transmitting Helicobacter pylori infection to their children. In an attempt to either prove or disprove this supposition, we investigated the rates of infection of children born to H. pylori-positive mothers from birth to 5 years of age using serology and the stool antigen test. When infection of the children did occur, the strains from the children were compared to those of their mothers using DNA analysis. Sixty-nine of the 350 pregnant mothers (19.7%) had a positive serology for H. pylori. Fifty-one children underwent serological examinations and stool antigen tests at 4 to 6 days after birth, followed by 1, 3, and 6 months. They were continuously given the stool antigen test at 4- to 6-month intervals until the age of 5 years. Gastric juice samples were collected from the infected children and their mothers for culture and DNA analyses using a random amplified polymorphic DNA fingerprinting method. None of the 51 children acquired H. pylori infection during the first year of life. Of the 44 children enrolled in a 5-year follow-up study, five (11%) acquired H. pylori infection. They acquired the infection at the age of 1 year 2 months, 1 year 3 months, 1 year 6 months, 1 year 8 months, and 4 years 4 months. Random amplified polymorphic DNA fingerprinting confirmed that the strains of the five children exhibited DNA fingerprinting patterns identical to those of their mothers. These findings suggest that mother-to-child transmission is the most probable cause of intrafamilial spread of H. pylori.
    Journal of Clinical Microbiology 06/2005; 43(5):2246-50. · 4.07 Impact Factor
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    ABSTRACT: We examined the macrolide susceptibility and the presence of macrolide-resistance genes in 780 Streptococcus pneumoniae strains that were isolated and collected at trunk hospitals and commercial clinical laboratories in Hokkaido prefecture, Japan, between 1999 and 2003. Of the 780 strains, 57.0% and 49.6% were found to bear the macrolide-resistance genes erm(B) and mef(A), respectively, while 87.9% had either or both of these genes. The mef(A)-positive strains were more frequently found in patients who were younger than 10 years (43.4%) compared to patients who were 10 years or older (30.3%), whereas the erm(B)-positive strains were similarly frequent in both groups (57.2% vs 54.9%). Strains that were extremely resistant to erythromycin (> or = 256 microg/ml) were frequently found in strains isolated at trunk hospitals but were rarely found in strains that had been collected at commercial clinical laboratories. In conclusion, the high frequency of emergence of macrolide resistance in S. pneumoniae strains was similar to reports from other areas of Japan and other east Asian countries. However, the distribution of resistant genes to macrolides and the distribution of the minimum inhibitory concentrations (MICs) differed depending on patients' ages and depending on whether the strains were isolated at trunk hospitals or commercial clinical laboratories.
    Journal of Infection and Chemotherapy 11/2004; 10(5):284-7. · 1.55 Impact Factor
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    ABSTRACT: We identified fluoroquinolone-resistant Streptococcus pneumoniae strains among 670 clinical isolates isolated from 1999 to 2003 in Hokkaido prefecture, Japan. All eleven stains were resistant to ciprofloxacin and levofloxacin. Furthermore, ten strains were also resistant to fluoroquinolones that are more effective with gram-positive bacteria, namely tosufloxacin, sparfloxacin, and gatifloxacin. Nucleotide sequence analysis of the quinolone-resistance determining region (QRDR) of the quinolone target genes coding for topoisomerase i.v. subunits (parC and parE) and DNA gyrase subunits (gyrA and gyrB). Eight stains, which showed higher resistance, had resistance mutations in two genes (gyrA and parC, or gyrA and parE), and other three strains had one resistance mutation in parC. The mutation patterns were varied between the strains. Data from random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) indicated that eleven strains were identified as ten independent clones. Lines of evidence indicated that genetic mutations leading to fluoroquinolone resistance occur sporadically rather through the spreading of a particular resistant strain. Notably, the fluoroquinolone-resistant strains were only isolated from adults, particularly from patients more than 60 years of age (9/60 strains; 15.0%). Resistant strains were not found in 574 strains isolates from patients under 20 years of age. This may be due to the fact that fluoroquionolones other than norfloxacin are not applicable to children in Japan.
    Kansenshogaku zasshi. The Journal of the Japanese Association for Infectious Diseases 06/2004; 78(5):428-34.
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    ABSTRACT: The etiology of Kawasaki disease (KD) remains unknown, although some infectious organism has been suggested as the cause. Recent studies suggest that some bacterial toxins with superantigen activity are involved in its pathogenesis, but no specific bacterial toxin has yet been identified. Throat swabs for bacterial culture were obtained from 21 patients with KD and 20 with other febrile illnesses as controls. Mitogenic activity in culture supernatants obtained from individual bacterial strains was measured by lymphocyte proliferation assay. Sixty-one bacterial strains were isolated from KD patients, and 62 strains from control patients. There was no apparent difference in bacterial species in the throat flora between KD patients and febrile controls. Moreover, total and individual mitogenic activity of strains from KD patients was no greater than that of strains from febrile controls. The bacterial superantigen activity of throat flora may not play a major role in the pathogenesis of KD.
    Microbiology and Immunology 02/2004; 48(11):899-903. · 1.55 Impact Factor
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    ABSTRACT: Kawasaki disease (KD) is an acute vasculitis of unknown etiology, however, some studies suggest that superantigens are involved in its pathogenesis. To clarify an association between KD and bacterial infection, we studied bacterial culture supernatants from throat flora of acute stage KD patients for mitogenic activity. Twenty-five individual bacterial strains (Streptococcus sp., Stapylococcus sp., Neisseria sp., Pseudomonas sp. etc) were isolated from throat of nine acute-stage KD patients before treatments. Each of these bacterial strains was cultured overnight at 37centigrade in trypticase soy broth. Bacterial cells were removed by centrifugation and filtration with a 0.22μm pore size filter. The mitogenic activity in the supernatants was determined by a three-day lymphocyte assay. Fresh peripheral blood mononuclear cells (PBMC) were obtained by ficoll-paque centrifugation of heparinized blood from healthy adult. PBMC were cultured in RPMI 1640 containing 10% heat-inactivated fetal bovine serum. The bacterial culture supernatant (10μL) was added to the PBMC culture (105 cells in 0.1 mL of culture medium) and then cultured in each well of a 96-well microplate at 37centigrade in 5% CO2. Proliferation of PBMC was determined three days after by morphological observation and Cell Counting Kit-8 (Dojin Chemical). The mitogenic activity for human lymphocytes was observed in three of twenty-five supernatants. The three supernatants were contained two strains of S. pyogenes and one strain of methicillin-resistant S. aureus. The results indicate that at least three of nine acute-stage KD patients had bacteria producing mitogenic products in throat flora. These findings support the involvement of mitogenic products, such as superantigens, of group A streptococci and S. aureus in the pathogenesis of KD.
    Pediatric Research 01/2003; 53(1):168-168. · 2.67 Impact Factor
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    ABSTRACT: We identified and genetically characterized seven fluoroquinolone-resistant Streptococcus pneumoniae strains among 293 clinical strains isolated from 1999 to 2001 in Japan. The resistant strains were isolated only from adults, and 7 of 31 isolates (22.6%) were from patients more than 20 years old. Resistant strains were not found in 262 isolates from children under age 10.
    Antimicrobial Agents and Chemotherapy 11/2002; 46(10):3311-5. · 4.57 Impact Factor

Publication Stats

132 Citations
28.50 Total Impact Points

Institutions

  • 2003–2009
    • Sapporo Medical University
      • • Department of Microbiology
      • • Department of Otolaryngology
      Sapporo, Hokkaidō, Japan
  • 2005
    • Hokkaido University
      • Department of Gastroenterology and Hepatology
      Sapporo, Hokkaidō, Japan