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Ann Lab Med. Nov 2012; 32(6): 413–419.
Published online Oct 17, 2012. doi:  10.3343/alm.2012.32.6.413
PMCID: PMC3486935
Clonal Spread of Carbapenem Non-susceptible Acinetobacter baumannii in an Intensive Care Unit in a Teaching Hospital in China
Qiao Zhong, M.D.,corresponding author Weidong Xu, M.D., Yuanjian Wu, M.D., and Hongxing Xu, M.D.
Department of Laboratory Medicine, Suzhou Municipal Hospital Affiliated Nanjing Medical University, Suzhou, China.
corresponding authorCorresponding author.
Corresponding author: Qiao Zhong. Department of Laboratory Medicine, Suzhou Municipal Hospital Affiliated Nanjing Medical University, 26 Daoqian Street, Suzhou, Jiangsu 215002, China. Tel: +86-512-62362312, Fax: +86-512-62362317, zhongqiao83/at/yahoo.com.cn
Received June 13, 2012; Revised July 2, 2012; Accepted September 16, 2012.
Abstract
Background
This study was aimed to investigate the genetic diversity and antibiotic resistance profile of the nosocomial infection agent Acinetobacter baumannii from a medical intensive care unit (ICU) in a teaching hospital in Suzhou, China.
Methods
The genetic relationship among A. baumannii isolates in an ICU was investigated using multilocus sequence typing (MLST). The antibiotic resistance pattern was determined by performing an antibiotic susceptible test, which included an agar dilution method and an E-test method. Resistant determinants, e.g., carbapenemase genes, metallo-β-lactamases, and class 1 integron, were analyzed by specific PCR and DNA sequencing.
Results
In the present study, 33 non-duplicate isolates were identified as 5 existing sequence types (STs) (ST92, ST75, ST112, ST145, and ST345) and 1 new sequence type STn, which has a G-A mutation at nt268 on ropD40 of ST251. These results reveal limited diversity in carbapenem non-susceptible A. baumannii (CNSAb) isolates in our ICU, which are comprised of only 2 distinct STs, with ST92 and ST75 clustering into a clonal complex (CC) 92. Most CNSAb isolates (94.4%, 17/18) harbored the OXA-23 gene, while no carbapenem-susceptible A. baumannii (CSAb) isolates harbored it. In addition, 66.7% (22/33) isolates were positive for class 1 integrase, and gene cassette analysis showed there are 3 gene arrays among them, i.e., aacA4-catB8-aadA1 (77.3%, 17/22), aacA4 (22.7%, 5/22), and aacC1-orfX-orfX'-aadA1 (4.5%, 1/22).
Conclusions
When all these data are combined, the antibiotic resistance and wide distribution of CNSAb isolates in our ICU are probably caused by expansion of the CC92 clone.
Keywords: MLST, Molecular epidemiology, Acinetobacter baumannii
Articles from Annals of Laboratory Medicine are provided here courtesy of
Korean Society for Laboratory Medicine