title: Prevalence of Smqnr and plasmid-mediated quinolone resistance determinants in clinical isolates of Stenotrophomonas maltophilia from Japan: novel variants of Smqnr.
abstract: Stenotrophomonas maltophilia is an important pathogen in healthcare-associated infections. S. maltophilia may contain Smqnr, a quinolone resistance gene encoding the pentapeptide repeat protein, which confers low-level quinolone resistance upon expression in a heterologous host. We investigated the prevalence of Smqnr and plasmid-mediated quinolone resistance (PMQR) determinants in S. maltophilia isolates from Japan. A total of 181 consecutive and nonduplicate clinical isolates of S. maltophilia were collected from four areas of Japan. The antimicrobial susceptibility profiles for these strains were determined. PCR was conducted for Smqnr and PMQR genes, including qnrA, qnrB, qnrC, qnrS, aac(6')-Ib and qepA. PCR products for Smqnr and aac(6')-Ib were sequenced. For the S. maltophilia isolates containing Smqnr, pulsed-field gel electrophoresis (PFGE) was performed using XbaI. Resistance rates to ceftazidime, levofloxacin, trimethoprim-sulfamethoxazole, chloramphenicol and minocycline were 67.4%, 6.1%, 17.7%, 8.8% and 0%, respectively. The minimum inhibitory concentration required to inhibit the growth of 50% and 90% of organisms were 0.5 and 2 mg/L for moxifloxacin but 1 and 4 mg/L for levofloxacin, respectively. Smqnr was detected in 104 of the 181 S. maltophilia isolates (57.5%), and the most frequent was Smqnr6, followed by Smqnr8 and Smqnr11. Eleven novel variants from Smqnr48 to Smqnr58 were detected. The 24 Smqnr-containing S. maltophilia isolates were typed by PFGE and divided into 21 unique types. Nine S. maltophilia isolates (5.0%) carried aac(6')-Ib-cr. No qnr or qepA genes were detected. This study describes a high prevalence of Smqnr and novel variants of Smqnr among S. maltophilia from Japan. Continuous antimicrobial surveillance and further molecular epidemiological studies on quinolone resistance in S. maltophilia are needed.
authors.affiliation: Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan ; Division of Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, NC, United States.
authors.forename: H
authors.initials: H
authors.lastname: Kanamori
authors.affiliation: Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yano
authors.affiliation: Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Tanouchi
authors.affiliation: Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Kakuta
authors.affiliation: Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Endo
authors.affiliation: Department of Bacteriology, BML Inc., Kawagoe, Saitama, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ichimura
authors.affiliation: Department of Bacteriology, BML Inc., Kawagoe, Saitama, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ogawa
authors.affiliation: Department of Bacteriology, BML Inc., Kawagoe, Saitama, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Shimojima
authors.affiliation: Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Inomata
authors.affiliation: Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
authors.forename: D
authors.initials: D
authors.lastname: Ozawa
authors.affiliation: Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Aoyagi
authors.affiliation: Division of Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, NC, United States.
authors.forename: D J
authors.initials: DJ
authors.lastname: Weber
authors.affiliation: Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kaku
keywords: Antimicrobial susceptibility; Japan; Smqnr; Stenotrophomonas maltophilia; plasmid-mediated quinolone resistance (PMQR)