Carbapenem-non-susceptible Acinetobacter baumannii of sequence type 92 or its single-locus variants with a G428T substitution in zone 2 of the rpoB gene.
OBJECTIVE
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 bla(OXA-23) gene (n = 169), the bla(OXA-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.
Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 250 Seongsanno, Seodaemun-gu, Seoul 120-752, Korea.
Yangsoon
Y
Lee
Jinhwa
J
Lee
Seok Hoon
SH
Jeong
Jonghan
J
Lee
Il Kwon
IK
Bae
Kyungwon
K
Lee
D000151:Acinetobacter Infections / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques; D015780:Carbapenems / Q000494:pharmacology*; D016000:Cluster Analysis; D003428:Cross Infection / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D005838:Genotype; D006761:Hospitals; D006801:Humans; D007723:Korea; D017720:Molecular Epidemiology / Q000379:methods; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D001618:beta-Lactamases / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D004269:DNA, Bacterial; D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit; D001618:beta-Lactamases