Comparison of three methods for the molecular typing of Singapore isolates of enterococci with high-level aminoglycoside resistances

Enterococci are frequently isolated as nosocomial pathogens and have often acquired intrinsic drug resistances. Molecular typing techniques have been developed to assist in epidemological and infection control measures. This study investigates enterococci with high-level aminoglycoside resistance (HLAR) from the National University Hospital (NUH) of Singapore, and evaluates and compares three methods for typing: restriction enzyme analysis by conventional gel electrophoresis [restriction fragment length polymorphism (RFLP)], pulsed-field gel electrophoresis (PFGE), and polymerase chain reaction (PCR) using random amplified polymorphic DNA (RAPD). Fifty-two isolates of Enterococcus faecalis and 13 isolates of Enterococcus faecium were used for the study. The numbers of patterns obtained for E., faecalis and E. faecium were 26 and 4, respectively by the RFLP method, and very similar discrimination was obtained by PFGE. RAPD PCR results were not reliably reproducible. A single pattern type by RFLP accounted for 16 of the E. faecalis isolates, suggesting hospital spread.