CLUSTERS OF NOSOCOMIAL CROSS-INFECTION DUE TO ACINETOBACTER-BAUMANNIIAND GENOSPECIES .3. COMPARISON OF SEROTYPING WITH MACRORESTRICTION ANALYSIS OF GENOMIC DNA WITH PULSED-FIELD GEL-ELECTROPHORESIS

Triplets of isolates representing 20 putative clusters of nosocomial c ross-infection due to Acinetobacter baumannii and genospecies 3 were e xamined comparatively using serotyping and analysis of restriction fra gments (SmaI and ApaI) of genomic DNA with the aid of pulsed-field gel electrophoresis. Carbon source assimilation tests disclosed phenotypi c variation among 6 of 20 triplets of isolates. Two misleading results of serotyping were encountered. With respect to the presumptive clust er No. 9, one of the genospecies 3 (originally serovar 4) isolates pro ved to be polyagglutinable upon repeat examination; this particular pu tative cluster was shown to be a pseudocluster by comparison of the ma crorestriction profiles of the respective triple isolates. A strain of A. baumannii serovar 15 had infected 8 patients in a surgical intensi ve care unit, while a second, genotypically totally different strain o f identical serovar had caused infection in one additional patient. Wi th this exception, the correlation between serotyping and analysis of macrorestriction profiles was excellent.