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Featured researches published by Ryoichi Hamasuna.


Clinical Infectious Diseases | 2008

Azithromycin Treatment Failure in Mycoplasma genitalium–Positive Patients with Nongonococcal Urethritis Is Associated with Induced Macrolide Resistance

Jørgen Skov Jensen; Catriona S. Bradshaw; Sepehr N. Tabrizi; Christopher K. Fairley; Ryoichi Hamasuna

BACKGROUNDnMycoplasma genitalium is a common cause of nongonococcal urethritis. Treatment trials have shown that doxycycline is inefficient, whereas a 5-day course of azithromycin eradicates the bacterium from 95% of infected men. The aim of the study was to establish the reason for the occasional treatment failures.nnnMETHODSnSeven M. genitalium strains isolated from men who experienced azithromycin treatment failure were tested for in vitro susceptibility to macrolides with use of a cell culture-based method. The genetic basis for the drug resistance was established by sequencing parts of the 23S ribosomal RNA gene and the genes encoding the L4 and L22 proteins. Nine sets of specimens obtained before and after treatment from patients who experienced azithromycin treatment failure were examined with use of sequencing of polymerase chain reaction products.nnnRESULTSnThe 7 strains that were isolated from patients who experienced treatment failure with azithromycin had minimum inhibitory concentrations >8 microg/mL for azithromycin and erythromycin. Three different mutations at positions 2058 and 2059 (Escherichia coli numbering) in region V of the 23S rRNA gene were found. Of the 9 patients with specimens obtained before and after treatment, only 2 had an initial specimen in which the mutation was present, indicating that drug resistance was induced as the result of an inappropriate dosage of azithromycin.nnnCONCLUSIONnDevelopment of macrolide resistance was shown to correlate with subsequent azithromycin treatment failure. The genetic basis for the drug resistance was shown to be mutations in region V of the 23S rRNA gene, which is well described in other Mollicutes. These findings raise concern about the use of single-dose azithromycin treatment of nongonococcal urethritis of unknown etiology.


International Journal of Urology | 2004

Bacteria of preoperative urinary tract infections contaminate the surgical fields and develop surgical site infections in urological operations.

Ryoichi Hamasuna; Hironori Betsunoh; Tetsuya Sueyoshi; Kazumichi Yakushiji; Hiromasa Tsukino; Masafumi Nagano; Toshiyuki Takehara; Yukio Osada

Background: The risk factors for surgical site infection (SSI) following urological operations have not been clearly identified, although the presence of a preoperative urinary tract infection (UTI) is thought to be one risk factor. We studied potential risk factors to clarify when and how bacteria contaminate wounds and SSI develop.


Sexually Transmitted Infections | 2008

Prevalence of Mycoplasma genitalium among female students in vocational schools in Japan

Ryoichi Hamasuna; Hirohisa Imai; Hiromasa Tsukino; Jørgen Skov Jensen; Yukio Osada

Objective: In Japan it was reported that about 9% of sexually active female teenagers had Chlamydia trachomatis. Most of them were asymptomatic, which may lead to continuing spread of the infection. Like C trachomatis, Mycoplasma genitalium is a pathogen in male non-gonococcal urethritis. However, few studies of the prevalence of M genitalium in the general population have been reported. The objective of this study was to determine the prevalence of M genitalium infection among younger females and to determine risk factors for this infection. Methods: The study was conducted between October 2005 and January 2006 using first voided urine specimens and questionnaires from female students of three vocational schools in the Miyazaki prefecture, Japan. C trachomatis was detected with Amplicor™ PCR. M genitalium was detected with inhibitor controlled real-time TaqMan™ PCR detecting the MgPa adhesion gene and with a PCR detecting the 16S rRNA. Risk factors associated with infection of M genitalium or C trachomatis were analysed with Fisher’s exact test. Results: Among 298 female, 249 (84%) had had experience of sexual intercourse. The prevalence of M genitalium was 2.8% (95% CI 0.76% to 4.86%) and the prevalence of C trachomatis was 8.8% (95% CI 5.31% to 12.36%). Conclusions: The risk factors of infection with M genitalium were more than five lifetime sexual partners and co-infection with C trachomatis.


International Journal of Std & Aids | 2010

Population-based study of asymptomatic infection with Chlamydia trachomatis among female and male students

Hirohisa Imai; Hiroyuki Nakao; Hisae Shinohara; Yoshinori Fujii; Hiromasa Tsukino; Ryoichi Hamasuna; Yukio Osada; K. Fukushima; M. Inamori; T. Ikenoue; Takahiko Katoh

There are few epidemiological studies of asymptomatic chlamydial infection among students in non-medical settings with minimal bias and improved accuracy; thus, useful data from screening among students are limited. We aimed to obtain accurate epidemiological information about asymptomatic chlamydial infection among students in non-medical settings. A population-based cross-sectional survey of 10,440 ≥18-year-old asymptomatic students who volunteered for a urine screening test for chlamydia was conducted. The prevalences of asymptomatic infection were 9.5% for women and 6.7% for men. Multivariate analysis revealed the risk factors to be a lifetime history of ≥4 sexual partners for women (odds ratio [OR] 3.17) and inconsistent condom use for men (OR 4.18). For both sexes, younger age at first intercourse was associated with a higher rate of inconsistent condom use. This study produced accurate epidemiological information on asymptomatic chlamydial infection. These results may contribute to the establishment of preventive countermeasures against such infection.


International Journal of Std & Aids | 2004

Prevalence and risk factors of asymptomatic chlamydial infection among students in Japan

Hirohisa Imai; Hisae Shinohara; Hiroyuki Nakao; Hiromasa Tsukino; Ryoichi Hamasuna; Takahiko Katoh

The objective was to determine the prevalence of asymptomatic Chlamydia trachomatis infection (CTI) among students in Japan, and to examine risk factors and methods of prevention. A total of 1004 students were analysed. Urine samples were checked for chlamydial DNA using polymerase chain reaction techniques. Prevalence of CTI was 8.3%. Risk factors were age and a history of four or more sexual partners for females, and history of CTI and contact with new sexual partners for males. Age did not represent a risk factor for male students. A correlation was identified between history of genital infection and experience with commercial sex workers for male students. Sex education programmes should be implemented encouraging use of condoms not only by students over 18 years, but also by senior high school students. Development of efficient and practical screening systems tailored to the current status of school health management in Japan is also needed.


International Journal of Urology | 2007

Usefulness of oral wash specimens for detecting Chlamydia trachomatis from high-risk groups in Japan

Ryoichi Hamasuna; Shinji Hoshina; Hirohisa Imai; Jørgen Skov Jensen; Yukio Osada

Abstract:u2003 Orogenital sex is recognized as a route for the transmission of Chlamydia trachomatis (CT) which thus causes male chlamydial urethritis. Patients with a pharyngeal CT infection have no gross lesions, but CT was tested by pharyngeal swabs. In this study, the usefulness of oral wash specimens for detecting CT was compared to that of swab specimens. In addition, oral wash specimens were also used to screen for CT pharyngeal infection. Eighteen female commercial sex workers in whom CT was detected from pharyngeal swabs were re‐examined using both methods. The positive rate for CT was 44% by swabs and 61% by oral wash specimens. Forty‐eight male students with CT‐positive urine were also screened for pharyngeal CT infection. The positive rates were 6% by swabs and 10% by oral wash specimens. Our findings therefore indicate that oral wash specimens more effectively detected pharyngeal CT infection than pharyngeal swabs.


The Journal of Urology | 1989

47,XXY/48,XXY,+21 Chromosomal Mosaicism Presenting as Hypospadias with Scrotal Transposition

Takanori Yamaguchi; Ryoichi Hamasuna; Yoshihiro Hasui; Shinichiro Kitada; Yukio Osada

The syndrome of 47,XXY/48,XXY,+21 chromosomal mosaicism, double aneuploidy, is extremely rare and characterized by combined manifestations of Klinefelters and Downs syndromes. We report a case of XXY/XXY,+21 mosaicism presenting with hypospadias associated with scrotal transposition.


Journal of Hospital Infection | 2004

High-level disinfection of cystoscopic equipment with ortho-phthalaldehyde solution.

K. Nose; T. Sueyoshi; Masafumi Nagano; Yoshihiro Hasui; Yukio Osada; Ryoichi Hamasuna


Urology | 2007

POS-03.06: Retroperitoneal laparoscopic nephrouretectomy for urothelial carcinoma of the renal pelvis and ureter

Masafumi Nagano; Toshio Kamimura; Hiromasa Tsukino; Hironobu Wakeda; K. Inoue; T. Kobayashi; Y. Yamashita; Ryoichi Hamasuna; Yoshihiro Hasui; Yukio Osada


Urology | 2007

MP-04.04: Glutathione S-transferase (GST) M1, T1 and N-acetyltransferase 2 (NAT2) polymorphisms and urothelial cancer risk with tobacco smoking

Hiromasa Tsukino; T. Katoht; Ryoichi Hamasuna; K. Nose; K. Inoue; Masafumi Nagano; Hironobu Wakeda; Toshio Kamimura; Yoshihiro Hasui; Yukio Osada

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K. Nose

University of Miyazaki

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K. Inoue

University of Miyazaki

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