Comparison of Six Methods for Epidemiological Typing of Escherichia coli Producing Extended-Spectrum Beta-Lactamase during a Suspected Outbreak

• 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.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Mikrobiologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Microbiology in the medical area (hsv//eng)

Nyckelord

Escherichia coli

extended-spectrum beta-lactamase

ESBL

epidemiological typing

typningsmetoder

ESBL

extended-spectrum beta-lactamase

Clinical bacteriology

Klinisk bakteriologi

Clinical Bacteriology

Klinisk bakteriologi

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)