Objectives: To investigate the epidemiological traits of carbapenem-non-susceptible Acinetobacter baumannii (CNSAB) and the usefulness of phylogenetic grouping based on partial rpoB gene sequencing in defining the epidemiological traits of CNSAB. Methods: A total of 547 non-duplicate clinical isolates of Acinetobacter spp. were collected from 19 hospitals in Korea in 2008. Detection of genes encoding OXA carbapenemases and metallo-β-lactamases was performed by PCR. The epidemiological relationships of the isolates were investigated by multilocus sequence typing and repetitive-sequence-based PCR. The 450 bp sequence (zone 2) of the rpoB gene was amplified and sequenced. Results: Molecular characterization of the 272 CNSAB isolates identified five sequence types (STs): ST92, ST75, ST137, ST138 and ST69. The first four of these STs were clustered into clonal complex (CC) 92, sharing alleles at six of seven housekeeping gene loci; ST69 shared alleles at five of seven loci. CNSAB of CC92 carried the blaOXA-23 gene (n=169), the blaOXA-51-like gene preceded by ISAba1 (n=89) or both (n=14). Notably, all CNSAB isolates carried a G428T substitution in zone 2 of the rpoB gene. Conclusions: CNSAB isolates of CC92 with the G428T substitution in zone 2 of the rpoB gene are disseminated nationwide in Korea. A. baumannii with the single nucleotide substitution may be more likely to acquire carbapenem resistance than are other isolates.
All Science Journal Classification (ASJC) codes
- Microbiology (medical)
- Infectious Diseases
- Pharmacology (medical)