Comparison of repetitive element sequence-based PCR with multilocus enzyme electrophoresis and pulsed field gel electrophoresis for typing Listeria monocytogenes food isolates

Repetitive element sequence-based PCR (rep-PCR) was compared with multilocus enzyme electrophoresis (MEE) and pulsed field gel electrophoresis (PFGE) for typing Listeria monocytogenes food isolates. All 45 L. monocytogenes food isolates were typable by rep-PCR using two primer sets (REP 1R-I REP 2-I and ERIC 1R ERIC 2), with good reproducibility though with less discriminatory power than MEE or PFGE. MEE and rep-PCR types were more stable than PFGE types over a given time period. All three typing methods usefully differentiated between closely related L. monocytogenes strains. Results obtained using rep-PCR concurred broadly with those obtained using MEE, while the former method proved to be more reproducibly and conveniently performed. The greater discriminatory power of PFGE enabled subtyping of rep-PCR and MEE types. When examining L. monocytogenes isolates collected over an extended period, the slightly less discriminatory but more stable electrophoretic types (ETs) distinguished by MEE are useful for confirmation and interpretation of PFGE data. However MEE is a cumbersome technique requiring a high degree of technical expertise in order to obtain reproducible results. In the present study rep-PCR conveniently and reliably produced typing data broadly congruent with that obtained using MEE which should prove useful in aiding interpretation of PFGE data for L. monocytogenes isolates obtained over extended time periods.