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 polymor phism (AFLP) analysis with pulsed-field gel electrophoresis (PFGE) with res pect 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 Enterococcus faecium (VRE) were ty ped by both methods. RESULTS: AFLP generated comparable results to PFGE for A baumannii and P ae ruginosa isolates; both methods identified epidemiologically related and un related isolates. However, strain typing of VRE isolates produced discordan t results between the two methods. PFGE identified 10 different strain type s and differentiated between all epidemiologically related and unrelated is olates. 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 meth od of choice (Infect Control Hosp Epidemiol 2001;22:550-554).