Efficacy of two DNA fingerprinting methods for typing Acinetobacter baumannii isolates

Performance of macrorestriction and repetitive extragenic palindromic DNA s equence-based PCR (REP-PCR) to type Acinetobacter baumannii isolates was qu antitatively estimated using a test population of 54 outbreak-related, 29 e ndemic infection-related and 17 epidemiologically-unrelated isolates. Repro ducibility and stability for macrorestriction were 100%, and REP-PCR showed only slightly lower stability. Macrorestriction resolved 18 fingerprints a nd REP-PCR 10 DNA patterns, forming eight and seven clusters at 75% of simi larity level, respectively. Intercluster band variation was >7 bands for bo th methods. Although, all endemic isolates, except one, were concordantly g rouped by both methods, macrorestriction distinguished a greater number of subtypes over one year study. For outbreaks, the epidemiologic concordance for both methods was 88%. The discriminatory index for macrorestriction and REP-PCR was 0.884 and 0.877, respectively. In conclusion, both methods sho wed similar efficacy as epidemiological markers, and by concordance, this s tudy demonstrated that for REP-PCR typing, a greater than or equal to7 band s difference seemed an appropriate threshold to identify unrelated strains. (C) 2001 Elsevier Science Inc. All rights reserved.