Naoki Wakiyama

Publications (3)5.41 Total impact

• Article: A retrospective study of the epidemiology of Clostridiumdifficile infection at a University Hospital in Japan: genotypic features of the isolates and clinical characteristics of the patients

  Yasuhito Iwashima, Atsushi Nakamura, Haru Kato, Hideaki Kato, Yukio Wakimoto, Naoki Wakiyama, Chiharu Kaji, Ryuzo Ueda
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  ABSTRACT: Clostridium difficile is a major cause of antibiotic-associated diarrhea and frequently results in healthcare-associated infections. The epidemiology of C. difficile infection (CDI), including the prevalent polymerase chain reaction (PCR) ribotypes and the clinical characteristics of the patients, is not well known in Japan, compared to the situation in the United States and Europe. We performed PCR ribotyping of C. difficile isolates from 71 consecutive patients with CDI at a University Hospital over a 3-year period and investigated the clinical features of those patients. CDI was diagnosed when a patient with diarrhea or colitis was found to have toxin B-positive C. difficile with no other enteropathogenic microorganisms. Toxin A-positive, toxin B-positive, binary toxin-positive (A+B+CDT+) strains; toxin A-positive, toxin B-positive, binary toxin-negative (A+B+CDT−) strains; and toxin A-negative, toxin B-positive, binary toxin-negative (A−B+CDT−) strains were isolated from 4, 58, and 9 patients, respectively, indicating that infections with binary toxin-positive strains were uncommon (5.6%). PCR ribotyping of the isolates demonstrated that among the 71 strains, 20 different PCR ribotypes were identified and that types smz, yok, and hr were predominant (19, 14, and 13 isolates, respectively), all of which were A+B+CDT−. No specific time periods or wards were found to be associated with the three types; PCR ribotyping analysis clearly showed that the three types spread almost evenly in all wards for the 3years studied. Comparative analysis of the clinical characteristics of patients harboring the three C. difficile types indicated that the duration of CDI was longer in the yok group than in the hr group. PCR ribotyping, which is easy to perform, appears to give us useful information to trace CDI cases in clinical settings. Further, the analysis of a large number of CDI cases may allow evaluation of the possible relationship between specific C. difficile types and the clinical features of patients. Keywords Clostridium difficile -PCR ribotyping-Binary toxin
  Journal of Infection and Chemotherapy 04/2012; 16(5):329-333. · 1.80 Impact Factor
• Article: Prevalence of a streptococcal inhibitor of a complement-mediated cell lysis-like gene (sicG) in Streptococcus dysgalactiae subsp. equisimilis.

  Masaaki Minami, Mariko Ichikawa, Hideyuki Matsui, Nanako Hata, Naoki Wakiyama, Masakado Matsumoto, Michio Ohta, Tadao Hasegawa
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  ABSTRACT: Streptococcus dysgalactiae subsp. equisimilis isolates (n = 110) were analyzed by PCR to determine whether the gene encoding SICG, a homolog of Streptococcus pyogenes SIC, was present. Nineteen strains (17%) had this gene of which 11 (55%) were isolated from patients with invasive disease. All 19 strains possessed group G carbohydrate. Molecular characterization of emm type revealed that the majority of emm sequences were stG643 and stG2078. Only the N-terminal sequence of SICG was similar to that of SIC in S. pyogenes. Although we found no significant relationship between pathogenic severity and sicG possession, further investigation into the mechanism of SICG may elucidate the virulence in S. dysgalactiae subsp. equisimilis infection.
  Current Microbiology 11/2010; 62(3):884-7. · 1.82 Impact Factor
• Article: A retrospective study of the epidemiology of Clostridium difficile infection at a University Hospital in Japan: genotypic features of the isolates and clinical characteristics of the patients.

  Yasuhito Iwashima, Atsushi Nakamura, Haru Kato, Hideaki Kato, Yukio Wakimoto, Naoki Wakiyama, Chiharu Kaji, Ryuzo Ueda
  [show abstract] [hide abstract]
  ABSTRACT: Clostridium difficile is a major cause of antibiotic-associated diarrhea and frequently results in healthcare-associated infections. The epidemiology of C. difficile infection (CDI), including the prevalent polymerase chain reaction (PCR) ribotypes and the clinical characteristics of the patients, is not well known in Japan, compared to the situation in the United States and Europe. We performed PCR ribotyping of C. difficile isolates from 71 consecutive patients with CDI at a University Hospital over a 3-year period and investigated the clinical features of those patients. CDI was diagnosed when a patient with diarrhea or colitis was found to have toxin B-positive C. difficile with no other enteropathogenic microorganisms. Toxin A-positive, toxin B-positive, binary toxin-positive (A(+)B(+)CDT(+)) strains; toxin A-positive, toxin B-positive, binary toxin-negative (A(+)B(+)CDT(-)) strains; and toxin A-negative, toxin B-positive, binary toxin-negative (A(-)B(+)CDT(-)) strains were isolated from 4, 58, and 9 patients, respectively, indicating that infections with binary toxin-positive strains were uncommon (5.6%). PCR ribotyping of the isolates demonstrated that among the 71 strains, 20 different PCR ribotypes were identified and that types smz, yok, and hr were predominant (19, 14, and 13 isolates, respectively), all of which were A(+)B(+)CDT(-). No specific time periods or wards were found to be associated with the three types; PCR ribotyping analysis clearly showed that the three types spread almost evenly in all wards for the 3 years studied. Comparative analysis of the clinical characteristics of patients harboring the three C. difficile types indicated that the duration of CDI was longer in the yok group than in the hr group. PCR ribotyping, which is easy to perform, appears to give us useful information to trace CDI cases in clinical settings. Further, the analysis of a large number of CDI cases may allow evaluation of the possible relationship between specific C. difficile types and the clinical features of patients.
  Journal of Infection and Chemotherapy 05/2010; 16(5):329-33. · 1.80 Impact Factor