The Limitations of Pulsed‐Field Gel Electrophoresis for Analysis of <i><scp>Y</scp>ersinia enterocolitica</i> Isolates

This study describes the analysis of 432 isolates of Yersinia enterocolitica by pulsed-field gel electrophoresis (PFGE). PFGE had a high level of discrimination with biotype 1A isolates (Simpson's Diversity Index 0.997), but with the clinically important biotypes 2, 3 and 4, the discriminatory ability of PFGE was so low as to severely limit its usefulness (DI <0.6). For biotypes 2, 3 and 4, 79% or more of isolates of each biotype were of just three different PFGE profiles. Because of this, four known outbreaks of yersiniosis would not have been identified by PFGE analysis. However, a previously unrecognized potential outbreak of yersiniosis caused by biotype 4 isolates was identified on the basis of a rare PFGE genotype with spatial and temporal clustering. We conclude that PFGE has a very limited application to the genotyping of Y. enterocolitica biotypes 2, 3 and 4, and inferences based on finding indistinguishable PFGE profiles among cases or between cases and sources need to be substantiated using alternative typing tools, or strong epidemiological evidence.