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Antimicrobial susceptibility patterns of enterococci in intensive care units in Sweden evaluated by different MIC breakpoint systems
Linköping University, Department of Molecular and Clinical Medicine, Clinical Microbiology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Molecular and Clinical Medicine, Infectious Diseases. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Molecular and Clinical Medicine, Infectious Diseases. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Molecular and Clinical Medicine, Infectious Diseases. Linköping University, Faculty of Health Sciences.
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2001 (English)In: Journal of Antimicrobial Chemotherapy, ISSN 0305-7453, E-ISSN 1460-2091, Vol. 48, no 1, 53-62 p.Article in journal (Refereed) Published
Abstract [en]

Three hundred and twenty-two (322) clinical isolates were collected from patients admitted to intensive care units (ICUs) at eight Swedish hospitals between December 1996 and December 1998. Of the isolates, 244 (76%) were Enterococcus faecalis, 74 (23%) were Enterococcus faecium and four (1%) were other Enterococcus spp. MICs of ampicillin, imipenem, meropenem, piperacillin/tazobactam, ciprofloxacin, trovafloxacin, clinafloxacin, gentamicin, streptomycin, vancomycin, teicoplanin, quinupristin/dalfopristin, linezolid and evernimicin were determined by Etest. Susceptible and resistant isolates were defined according to the species-related MIC breakpoints of the British Society for Antimicrobial Chemotherapy (BSAC), the National Committee for Clinical Laboratory Standards (NCCLS) and the Swedish Reference Group for Antibiotics (SRGA). Tentative breakpoints were applied for new/experimental antibiotics. Multidrug resistance among enterococci in ICUs is not uncommon in Sweden, particularly among E. faecium, and includes ampicillin resistance and concomitant resistance to fluoroquinolones. Almost 20% of E. faecalis isolates showed high-level resistance to gentamicin and concomitant resistance to fluoroquinolones. Vancomycin-resistant enterococci were only found sporadically. Among the new antimicrobial agents, linezolid and evernimicin showed the best activity against all enterococcal isolates. There was good concordance between the BSAC, NCCLS and SRGA breakpoints in detecting resistance. When applying the SRGA breakpoints for susceptibility, isolates were more frequently interpreted as intermediate. This might indicate earlier detection of emerging resistance using the SRGA breakpoint when the native population is considered susceptible, but with the risk that isolates belonging to the native susceptible population will be incorrectly interpreted as intermediate.

Place, publisher, year, edition, pages
2001. Vol. 48, no 1, 53-62 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-25743DOI: 10.1093/jac/48.1.53Local ID: 10175OAI: oai:DiVA.org:liu-25743DiVA: diva2:246291
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-09-28Bibliographically approved
In thesis
1. Enterococci in Swedish intensive care units: studies on epidemiology, mechanisms of antibiotic resistance and virulence factors
Open this publication in new window or tab >>Enterococci in Swedish intensive care units: studies on epidemiology, mechanisms of antibiotic resistance and virulence factors
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The purpose of this thesis was to study enterococci in Sweden, their resistance to antibiotics in general and high-level gentamicin resistance (HLGR) in particular, with a special focus on the ICU setting. Dynamics of rectal colonisation during prolonged intensive care unit (ICU) stay was assessed. In addition, enterococcal virulence factors and the ability to adhere to abiotic surfaces such as urinary catheters were studied.

We found that among prolonged-stay patients admitted to ICUs, the rectal flora was altered, with a decrease in Gram-negative rods in favour of Gram-positive bacteria, mainly Coagulase negative staphylococci and enterococci.

Among clinical enterococcal isolates from patients admitted to Swedish ICUs, although vancomycin resistant enterococci (VRE) were only sporadically found, multidrug resistance was common. This was most apparent in Enterococcus faecium, where the majority of isolates were ampicillin- and quinolone resistant. Enterococcus faecalis was still the most frequently isolated enterococcal species in clinical specimens. Among patients admitted to Swedish ICUs 1996-1998, E. faecalis with HLGR was found in higher frequency (20%) than previously reported. The majority (89%) of these isolates belonged to two dominating clusters of genetically related E. faecalis. Cluster I (69%), which was predominantly found in the eastern and central parts of southern Sweden and Cluster II (20%) in south-western Sweden.

In the County of Östergötland, the first E. faecalis with HLGR isolated from blood cultures was found in 1996. The yearly incidence of isolates with HLGR in E. faecalis bacteraemia was studied from 1996-2001, and varied between 9-22%. The majority of these isolates were genetically related and belonged to Cluster I, also found in the previous study. The first blood isolate of E. faecium with HLGR in the County of Östergötland was found in 1999. A clone of E. faecium, with HLGR and ampicillin resistance, was found to colonise 6/10 and 2/11 prolonged-stay patients admitted from November 2001 through January 2002 to the general ICU and cardio-thoracic ICU, respectively, at the University Hospital of Linköping.

All studied isolates with HLGR carried the gene aac(6')-Ie-aph(2'')-Ia encoding the bifunctional aminoglycoside modifying enzyme Aac(6')Ie-Aph(2'')Ia, which conveys resistance to all commercially available amino-glycosides except streptomycin. The location of the gene, aac(6')Ie-aph(2'')-Ia, was studied in 45 E. faecalis isolates and the gene was carried on a Tn5281-like transposon in all isolates except one. The 30 µg disc diffusion test, as recommended by the SRGA, had 100% sensitivity and specificity when compared to PCR detection of aac(6')-Ie-aph(2'')-Ia.

E. faecalis isolates with HLGR belonging to widely disseminated clusters of genetically related isolates were more likely to carry both the gene encoding enterococcal surface protein (esp) and the gene encoding aggregation substance (asa1) compared to unique isolates. Esp was the only virulence factor found among E. faecium isolates, where it was common. E. faecalis isolates adhered with higher bacterial densities to urinary tract catheters compared to E. faecium isolates. In vitro adherence to urinary tract catheters was not affected by esp.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2005. 99 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 880
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-28709 (URN)13876 (Local ID)91-737-3861-1 (ISBN)13876 (Archive number)13876 (OAI)
Public defence
2005-02-18, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings Universitet, Linköping, 13:00 (English)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-09-28Bibliographically approved

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Hällgren, AnitaEkdahl, ChristerHanberger, HåkanNilsson, MaudSamuelsson, AnnikaNilsson, Lennart

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