Multilocus sequence typing versus pulsed-field gel electrophoresis for characterization of extended-spectrum beta-lactamase-producing Escherichia coli isolates - PubMed (original) (raw)

Comparative Study

Multilocus sequence typing versus pulsed-field gel electrophoresis for characterization of extended-spectrum beta-lactamase-producing Escherichia coli isolates

Lucia L Nemoy et al. J Clin Microbiol. 2005 Apr.

Abstract

Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli strains are emerging pathogens. Molecular typing of ESBL-producing E. coli is useful for surveillance purposes, to monitor outbreaks and track nosocomial spread. Although pulsed-field gel electrophoresis (PFGE) is the current "gold standard" for bacterial molecular typing, multilocus sequence typing (MLST) may offer advantages. Forty ESBL-producing E. coli isolates were selected at random from a cohort of intensive care unit patients who had active surveillance perirectal cultures done. PFGE identified 19 unique PFGE types (PT) among the 40 isolates; MLST identified 22 unique sequence types. MLST had greater discriminatory ability than PFGE for ESBL-producing E. coli. Simpson's indices of diversity for PFGE and MLST were 0.895 and 0.956, respectively. There were five clonal complexes (CCs) (isolates with differences of no more than two loci) that each contained multiple PT, but each PT was found in only one CC, indicating genetic consistency within a CC. MLST has clear utility in studies of ESBL-producing E. coli, based on a greater discriminatory ability and reproducibility than PFGE and the ability to a priori define genetically related bacterial strains.

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Figures

FIG. 1.

PFGE dendrogram with the corresponding MLST sequence types of the ESBL-producing E. coli isolates. Each row represents a unique PFGE type with its unique PFGE pattern. The corresponding MLST sequence type (ST) is similarly shown with the isolate number(s). For example, the first row depicts PFGE type 1 (P01) which corresponded to MLST ST-04 and ST-06 from isolates 6 and 52.

FIG. 2.

MLST dendrogram of ESBL-producing E. coli isolates. The 40 ESBL E. coli isolates are shown and labeled as isolate number, sequence type (ST), and allelic profile in parentheses. Isolates with identical STs are shown on the same vertical branch. There are five CCs defined as isolates with the identical ST or a ST that differ at no more than two loci.

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Multilocus sequence typing versus pulsed-field gel electrophoresis for characterization of extended-spectrum beta-lactamase-producing Escherichia coli isolates - PubMed (original) (raw)