Colonization of a medical center in Southern Taiwan by epidemic strains of carbapenem- and multidrug-resistant Acinetobacter baumannii and the genetic organization of their integrons.

A total of 46 carbapenem- and multidrug-resistant (CR- and MDR-)Acinetobacter baumannii bacteremic isolates from a Taiwanese medical center were investigated over the period 2000 to 2006 using randomly amplified polymorphic DNA (RAPD) profiling and by analysing the genetic organization of their integrons. The results of RAPD patterns revealed that before 2003 each CR- and MDR-A. baumannii bacteremic isolate was independent, but after 2003 the isolates appeared to belong in four epidemic strains and persisted in the hospital. All the CR- and MDR-A. baumannii strains harbored class I integron (intI1) genes. PCR amplification and nucleotide sequencing showed that the cassette genes of intI1 were found to form four different antibiotic-resistant gene alignments in those strains. The bla(IMP-1) gene in the cassette genes of intI1 was identified in a clone, which raised great concern that clonal spread of this strain or of an integron-mediated horizontal gene may have occurred.