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Antibiotic susceptibility among Staphylococcus epidermidis isolated from prosthetic joint infections with special focus on rifampicin and variability of the rpoB gene
Örebro University, School of Health and Medical Sciences.
Örebro University, School of Health and Medical Sciences.ORCID iD: 0000-0001-5939-2932
2009 (English)In: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 15, no 3, 238-244 p.Article in journal (Refereed) Published
Abstract [en]

Staphylococcus epidermidis is the most important pathogen in infections related to implanted foreign materials, especially prosthetic joint infections (PJIs). The aim of this study was to investigate the antimicrobial activities of 16 antibiotics against S. epidermidis isolated from PJIs, with special focus on rifampicin and rpoB variability. Ninety-one per cent of the isolates were multiresistant (i.e. resistant to members of more than three classes of antibiotics). Thirty-nine per cent were resistant to rifampicin, associated with one or two single-nucleotide polymorphisms (SNPs) in rpoB. Using IsoSensitest agar with supplements, 61% were resistant to oxacillin, and using Mueller-Hinton II agar with supplement, 84% were resistant. Using the Etest, 58% were resistant to cefoxitin, and using the disk diffusion test, 91% were resistant. The mecA gene was detected in 85% of the isolates. Regarding recently available antibiotics, all isolates were susceptible to tigecycline and linezolid, and 97% were susceptible to daptomycin. In addition, two novel antibiotics, dalbavancin and ceftobiprole, were tested, although not yet available for routine use. The MIC(50) and MIC(90) values of these novel antibiotics were 0.032 and 0.047 mg/L and 0.5 and 1.5 mg/L, respectively. Among the other antibiotics, the rates of resistance varied between 0% (vancomycin) and 82% (trimethoprim-sulphamethoxazole). S. epidermidis strains causing PJIs often show multiresistance, including resistance to rifampicin, which is mainly caused by one or two SNPs. Some of the newer antimicrobial agents may provide alternatives for monotherapy or combination therapy with rifampicin. Detection of mecA is necessary before initiating treatment of infections due to S. epidermidis when it displays intermediate susceptibility to cefoxitin.

Place, publisher, year, edition, pages
Oxford: Blackwell , 2009. Vol. 15, no 3, 238-244 p.
National Category
Medical and Health Sciences Infectious Medicine
Research subject
Biomedicine
Identifiers
URN: urn:nbn:se:oru:diva-11784DOI: 10.1111/j.1469-0691.2008.02663.xPubMedID: 19196261OAI: oai:DiVA.org:oru-11784DiVA: diva2:349804
Available from: 2010-09-08 Created: 2010-09-08 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Genotypic and phenotypic characterisation of Staphylococcus epidermidis isolated from prosthetic joint infections
Open this publication in new window or tab >>Genotypic and phenotypic characterisation of Staphylococcus epidermidis isolated from prosthetic joint infections
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Staphylococcus epidermidis has emerged in recent years as an important nosocomial pathogen, especially in infections associated with implanted foreign body materials (e.g., prosthetic joints and heart valves) and in individuals with a compromised immune system (e.g., cancer patients and neonates). Although rare, implant infections are long lasting and cause severe suffering for the patient that includes pain and disability and even increased mortality. One aim of the present thesis was to develop and evaluate a genetic method for species identification and simultaneous detection of rifampicin resistance in staphylococci. A second aim was to examine S. epidermidis isolated from prosthetic joint infections (PJIs) and from wrists and nares of healthy individuals regarding their antibiotic susceptibility, biofilm production, virulence factors, and epidemiology. Comparison with phenotypic diagnostics revealed that 8 (16%) of 49 isolates differed in their species identification in favour of the genetic method. In addition, mutations associated with rifampicin resistance, including two not previously reported, were possible to detect in all isolates resistant to rifampicin. Antibiotic susceptibility testing of 61 PJI isolates showed multi-drug resistance in 91%. Furthermore, the results of the synergy testing revealed that no antibiotic combination was significantly better than the others. Hence, the effects that were possible to detect were isolate dependent. To find a method for discriminating between invasive (n=61) and commensal (n=24) isolates of S. epidermidis genotypic and phenotypic characterisations of biofilm production (including the ica and aap genes), antibiotic susceptibility, virulence-related genes (such as agr and ACME) and epidemiology were performed (using multilocus sequence typing [MLST], typing of the staphylococcal chromosome cassette mec [SCCmec] and PhenePlate). Significant differences were found in antibiotic susceptibility, i.e. there was more resistance among invasive isolates. MLST sequence types (ST) ST2 and ST215 dominated the invasive isolates.

Place, publisher, year, edition, pages
Örebro: Örebro universitet, 2011. 117 p.
Series
Örebro Studies in Medicine, ISSN 1652-4063 ; 53
Keyword
Staphylococcus epidermidis, prosthetic joint infections, antibiotic susceptibility, virulence factors, epidemiology, MLST, agr, SCCmec
National Category
Medical and Health Sciences
Research subject
Biomedicine
Identifiers
urn:nbn:se:oru:diva-15171 (URN)978-91-7668-793-2 (ISBN)
Public defence
2011-05-13, Wilandersalen, Universitetssjukhuset, Örebro, 09:00
Opponent
Supervisors
Available from: 2011-04-01 Created: 2011-04-01 Last updated: 2017-10-17Bibliographically approved

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Hellmark, BengtUnemo, MagnusSöderquist, Bo

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