title: The DiversiLab system versus pulsed-field gel electrophoresis: characterisation of extended spectrum β-lactamase producing Escherichia coli and Klebsiella pneumoniae.
abstract: Fast and reliable epidemiological typing methods for identifying outbreaks and epidemic strains of extended spectrum β-lactamase (ESBL) producing Enterobacteriaceae are urgently needed. The DiversiLab system (DL) has been proposed for these purposes. We compared DL to pulsed-field gel electrophoresis (PFGE) on a national collection of ESBL-producing Escherichia coli (n=258; of which 226 isolates were typeable with PFGE) and Klebsiella pneumoniae (n=48) isolated in 2007. For E. coli the Wallace coefficients showed that the probability of two isolates of the same DL type having the same PFGE type was only 19.8% and the probability of two isolates of the same PFGE type having the same DL type was 90.4%. For K. pneumoniae the Wallace coefficients showed that the probability of two isolates of the same DL type having the same PFGE type was 100% and the probability of two isolates of the same PFGE type having the same DL type was 79%, indicating that for this K. pneumoniae strain collection DL was slightly more discriminatory. Only four of 48 isolates had discordant results with the two methods. In E. coli 42% of the isolates were sequence type 131 and these isolates were related at >95% similarity with DL and at ≥60% similarity with PFGE. In summary, for E. coli DL performed well in identifying isolates related by PFGE, but overestimated the genetic relatedness in the studied collection. This indicates that DL could be a primary screening method for excluding unrelated isolates. Isolates shown to be related must be confirmed with a more discriminatory method. For K. pneumoniae, DL discriminated well but overestimated the diversity of the isolates compared to PFGE, assuming a risk of missing possible genetic relatedness.
authors.affiliation: Swedish Institute for Infectious Disease Control, Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.
authors.forename: Alma
authors.initials: A
authors.lastname: Brolund
authors.forename: Sara
authors.initials: S
authors.lastname: Hæggman
authors.forename: Petra J
authors.initials: PJ
authors.lastname: Edquist
authors.forename: Lena
authors.initials: L
authors.lastname: Gezelius
authors.forename: Barbro
authors.initials: B
authors.lastname: Olsson-Liljequist
authors.forename: Karin Tegmark
authors.initials: KT
authors.lastname: Wisell
authors.forename: Christian G
authors.initials: CG
authors.lastname: Giske
mesh_terms: D015373:Bacterial Typing Techniques / Q000379:methods*; D016000:Cluster Analysis; D016172:DNA Fingerprinting / Q000379:methods*; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000145:classification* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D007710:Klebsiella Infections / Q000453:epidemiology / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000145:classification* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D058889:Molecular Typing / Q000379:methods; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D001618:beta-Lactamases