Comparison of Pulsed-Field Gel Electrophoresis and Amplified Fragment-Length Polymorphism for Epidemiological Investigations of Common Nosocomial Pathogens

OBJECTIVE: To compare molecular typing by amplified fragment-length polymorphism (AFLP) analysis with pulsed-field gel electrophoresis (PFGE) with respect to the ability to differentiate between epidemiologically related and unrelated isolates of common nosocomial pathogens recovered during a period of endemicity. DESIGN: Retrospective laboratory analysis. SETTING: Tertiary-care institution. METHODS: 17 isolates of Acinetobacter baumannii, 22 isolates of Pseudomonas aeruginosa, and 22 vancomycin-resistant Enterococcusfaecium (VRE) were typed by both methods. RESULTS: AFLP generated comparable results to PFGE for A baumannii and P aeruginosa isolates; both methods identified epidemiologically related and unrelated isolates. However, strain typing of VRE isolates produced discordant results between the two methods. PFGE identified 10 different strain types and differentiated between all epidemiologically related and unrelated isolates. In contrast, AFLP generated only five different strain types, three of which contained both epidemiologically related and unrelated isolates. CONCLUSION: Molecular typing by AFLP is comparable to PFGE for A baumannii and P aeruginosa isolates. For VRE isolates, however, PFGE remains the method of choice.