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Genotypic and phenotypic characterisation of Staphylococcus epidermidis isolated from prosthetic joint infections
Örebro University, School of Health and Medical Sciences.
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 [sv]
Staphylococcus epidermidis, prosthetic joint infections, antibiotic susceptibility, virulence factors, epidemiology, MLST, agr, SCCmec
National Category
Medical and Health Sciences
Research subject
Biomedicine
Identifiers
URN: urn:nbn:se:oru:diva-15171ISBN: 978-91-7668-793-2OAI: oai:DiVA.org:oru-15171DiVA: diva2:407775
Public defence
2011-05-13, Wilandersalen, Universitetssjukhuset, Örebro, 09:00
Opponent
Supervisors
Available from: 2011-04-01 Created: 2011-04-01 Last updated: 2011-06-20Bibliographically approved
List of papers
1. Simultaneous species identification and detection of rifampicin resistance in staphylococci by sequencing of the rpoB gene
Open this publication in new window or tab >>Simultaneous species identification and detection of rifampicin resistance in staphylococci by sequencing of the rpoB gene
2008 (English)In: European Journal of Clinical Microbiology and Infectious Diseases, ISSN 0934-9723, E-ISSN 1435-4373, Vol. 28, no 2, 183-190 p.Article in journal (Refereed) Published
Abstract [en]

In recent years, coagulase-negative staphylococci (CoNS) have been increasingly recognised as causative agents of various infections, especially in immunocompromised patients and related to implanted foreign body materials. In this study, rpoB sequencing was used for simultaneous species identification and detection of rifampicin resistance in clinical staphylococci isolates. Forty-nine (96%) out of 51 isolates, representing 17 different Staphylococcus species according to the initial phenotypic species identification, were identified to the species level using rpoB sequencing. Furthermore, the two remaining isolates were Kocuria sp. and Corynebacterium sp. respectively, according to 16S rRNA sequencing. Comparison with the phenotypic diagnostics also revealed that 8 (16%) of the 49 isolates differed regarding identified species. Discrepant analysis confirmed the result of the rpoB sequencing for all except 2 of these isolates, which could not be distinguished as single species using 16S rRNA sequencing. Regarding detection of rifampicin resistance, isolates obtained pre- and post-treatment with rifampicin were examined. These isolates comprised S. aureus (7 patients) and S. lugdunensis (1 patient). Rifampicin resistance was mainly detected following short-term treatment with rifampicin in combination with isoxazolyl-penicillin, or long-term treatment with rifampicin and ciprofloxacin. Each rifampicin-resistant isolate displayed an identical rpoB sequence as their corresponding rifampicin-susceptible isolates except for one (n = 6) or two (n = 1) nonsynonymous single nucleotide polymorphisms, or insertion of one codon (n = 1). In conclusion, rpoB sequencing is a rapid, objective and accurate method of species identification and simultaneous detection of rifampicin resistance in staphylococci.

Place, publisher, year, edition, pages
Berlin: Springer, 2008
National Category
Medical and Health Sciences Microbiology in the medical area
Research subject
Biomedicine
Identifiers
urn:nbn:se:oru:diva-3467 (URN)10.1007/s10096-008-0604-5 (DOI)18716806 (PubMedID)
Available from: 2008-12-08 Created: 2008-12-08 Last updated: 2011-06-20Bibliographically approved
2. Antibiotic susceptibility among Staphylococcus epidermidis isolated from prosthetic joint infections with special focus on rifampicin and variability of the rpoB gene
Open this publication in new window or tab >>Antibiotic susceptibility among Staphylococcus epidermidis isolated from prosthetic joint infections with special focus on rifampicin and variability of the rpoB gene
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
National Category
Medical and Health Sciences Infectious Medicine
Research subject
Biomedicine
Identifiers
urn:nbn:se:oru:diva-11784 (URN)10.1111/j.1469-0691.2008.02663.x (DOI)19196261 (PubMedID)
Available from: 2010-09-08 Created: 2010-09-08 Last updated: 2011-06-20Bibliographically approved
3. In vitro antimicrobial synergy testing of coagulase-negative staphylococci isolated from prosthetic joint infections using Etest and with a focus on rifampicin and linezolid
Open this publication in new window or tab >>In vitro antimicrobial synergy testing of coagulase-negative staphylococci isolated from prosthetic joint infections using Etest and with a focus on rifampicin and linezolid
2010 (English)In: European Journal of Clinical Microbiology and Infectious Diseases, ISSN 0934-9723, E-ISSN 1435-4373, Vol. 29, no 5, 591-595 p.Article in journal (Refereed) Published
Abstract [en]

In recent years, coagulase-negative staphylococci (CoNS) have been increasingly recognised as causative agents of various infections, especially in immunocompromised patients and related to implanted foreign body materials. CoNS, and especially Staphylococcus epidermidis, transform into a stationary growth phase and produce biofilm when involved in a foreign body infection, making them difficult to eradicate with antimicrobials. Rifampicin has the ability to penetrate biofilm, but resistance may develop rapidly. To reduce the emergence of resistance, rifampicin should be combined with additional antimicrobials, of which several different ones have been proposed, including the relatively new class of antimicrobials, oxazolidinones, represented by linezolid. Thirty-seven CoNS isolates from patients with prosthetic joint infection were investigated by synergy testing using Etest. Nine antimicrobial combinations, based on either rifampicin or linezolid, were tested. For 16 (43%) of the isolates, a synergistic (n = 5), additive (n = 14) and/or antagonistic (n = 11) effect were identified. In conclusion, Etest is an objective and easily performed in vitro method for antimicrobial synergy testing. However, each isolate requires testing for the specific combination considered for treatment.

Place, publisher, year, edition, pages
Berlin: Springer, 2010
National Category
Medical and Health Sciences Infectious Medicine
Research subject
Infectious Diseases; Biomedicine
Identifiers
urn:nbn:se:oru:diva-15250 (URN)10.1007/s10096-010-0902-6 (DOI)20221891 (PubMedID)
Available from: 2011-04-13 Created: 2011-04-13 Last updated: 2011-06-20Bibliographically approved
4. Comparison of Staphylococcus epidermidis isolated from prosthetic joint infections commensal isolates in regards to antibiotic susceptibility, agr type, biofilm production, and epidemiology
Open this publication in new window or tab >>Comparison of Staphylococcus epidermidis isolated from prosthetic joint infections commensal isolates in regards to antibiotic susceptibility, agr type, biofilm production, and epidemiology
(English)Manuscript (preprint) (Other academic)
National Category
Medical and Health Sciences Infectious Medicine
Research subject
Infectious Diseases
Identifiers
urn:nbn:se:oru:diva-15251 (URN)
Available from: 2011-04-13 Created: 2011-04-13 Last updated: 2012-12-14Bibliographically approved
5. SCCmec and ACME in Staphylococcus epidermidis isolated from prosthetic joint infections
Open this publication in new window or tab >>SCCmec and ACME in Staphylococcus epidermidis isolated from prosthetic joint infections
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Medical and Health Sciences Infectious Medicine
Research subject
Biomedicine
Identifiers
urn:nbn:se:oru:diva-15252 (URN)
Available from: 2011-04-13 Created: 2011-04-13 Last updated: 2011-06-20Bibliographically approved

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