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Comparison of Six Methods for Epidemiological Typing of Escherichia coli Producing Extended-Spectrum Beta-Lactamase during a Suspected Outbreak
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Bacteriology. (Björn Olsen)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Bacteriology. (Björn Olsen)
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

During a suspected outbreak of Escherichia coli producing extended-spectrum beta-lactamase (ESBL) at Uppsala University Hospital 2005-2007, different typing methods were applied to examine their usefulness in a sharp situation. Included methods were antibiogram-based typing, PhenePlate (PhP) system, pulsed-field gel electrophoresis (PFGE), repetitive sequence-based (rep)-PCR (Diversilab), arbitrarily primed (AP)-PCR, and characterization of integrons. A PCR assay was used to define the O25b-ST131 clone, and nosocomial transmission was explored with a locally developed tracing tool. Of the 253 analyzed isolates, 70% harboured CTX-M group 1 enzymes and 19% CTX-X-M group 9 enzymes. Integrons with integrated gene cassettes were detected in 47% of the isolates and 77% were of class 1. One restriction fragment length polymorphism (RFLP) type predominated (n=48), and it was in 40% of the cases associated with the O25b-ST131 clone. Fifty-five (22%) of all isolates were PCR positive for this clone, of which the PhP-system identified 49%. Fifty isolates were further analyzed. Most methods had difficulties with recognizing the O25b-ST131 clone. Rep-PCR identified 100%, PFGE 86%, AP-PCR 68%, PCR-RFLP of integrons 39% and antibiogram types 32% of the PCR positive isolates. Epidemiological data supported a nosocomial transmission in a limited number of cases, suggesting an endemic rather than an epidemic situation. In conclusion, the genetic complexity of ESBL-producing E. coli has become a challenge for any microbiology laboratory. Although the defining O25b-ST131 PCR assay was the most efficient method to identify this epidemic clone, PCR methods cannot be applied on genetically uncharacterized E. coli strains. To rely on a single epidemiological typing method to identify strains or mobile genetic elements with epidemic potential might be insufficient.

Keyword [en]
Escherichia coli, extended-spectrum beta-lactamase, ESBL, epidemiological typing
Keyword [sv]
typningsmetoder, ESBL, extended-spectrum beta-lactamase
National Category
Microbiology in the medical area
Research subject
Clinical Bacteriology
Identifiers
URN: urn:nbn:se:uu:diva-132228OAI: oai:DiVA.org:uu-132228DiVA: diva2:357274
Available from: 2010-10-16 Created: 2010-10-16 Last updated: 2011-01-13
In thesis
1. Enterobacteriaceae Producing Extended-Spectrum Beta-Lactamases: Aspects of Detection, Epidemiology and Control
Open this publication in new window or tab >>Enterobacteriaceae Producing Extended-Spectrum Beta-Lactamases: Aspects of Detection, Epidemiology and Control
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Enterobacteriaceae belong to the normal enteric flora in humans and may cause infections. Escherichia coli is the leading urinary tract pathogen with septicaemic potential, whereas Klebsiella pneumoniae causes opportunistic infections and often outbreaks in hospital settings. Beta-lactams are the first choice for treatment of infections caused by Enterobacteriaceae, and might be destroyed by extended-spectrum beta-lactamases, ESBLs. ESBLs hydrolyse all beta-lactams except cephamycin and carbapenems, and constitute a large heterogeneous group of enzymes with different origins. The phenotypic and molecular characteristics of a K. pneumoniae strain causing a major outbreak at Uppsala University Hospital between 2005 and 2008 were described. The strain was multiresistant and produced CTM-M-15, a common ESBL type in Europe. Due to the lack of obvious epidemiological links between patients, a case-control study was performed, which identified risk factors for the acquisition of the outbreak strain in urine cultures. The complex chain of transmission facilitated by patient overcrowding and the interventions applied to curb the outbreak, was revealed in the subsequent study. In the final study, the genetic background of the observed increase in ESBL-producing E. coli isolates during the K. pneumoniae outbreak was explored. The utility of six typing methods in epidemiological investigations of a local outbreak with ESBL-producing E. coli was compared. The increase of ESBL-producing E. coli isolates was not secondary to the K. pneumoniae outbreak. Twentytwo per cent belonged to the epidemic O25b-ST131 clone and only a limited number of infections were caused by nosocomial transmission. ESBL-producing Enterobacteriaceae are a challenge to clinical microbiology laboratories and infection control teams. To investigate their dissemination, typing methods need to be continuously adapted to the current situation. Proper hand disinfection and structural key problems such as over-crowding, under-staffing, lack of single rooms and bathrooms must be adressed to limit transmission.

 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 57 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 610
Keyword
Extended-spectrum beta-lactamase, ESBL, pulse-field gel elctrophoresis, typing methods, infection control, typningsmetoder, vårdhygien
National Category
Microbiology in the medical area
Research subject
Clinical Bacteriology
Identifiers
urn:nbn:se:uu:diva-131901 (URN)978-91-554-7922-0 (ISBN)
Public defence
2010-12-03, Hörsalen, Klinisk mikrobiologi, Dag Hammarskölds väg 17, Uppsala, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2010-11-12 Created: 2010-10-09 Last updated: 2011-01-13Bibliographically approved

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