Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 5/21/2011
Publication Date: 5/21/2011
Citation: Huang, X.Z., Chahine, M.A., Frye, J.G., Cash, D.M., Summer, A.M., Lesho, E.P., Craft, D.W., Lindler, L.E., Nikolich, M.P. 2011. Molecular characteristics of Multidrug Resistant Acinetobacter baumannii Isolates from US soldiers from Iraq at the National Naval Medical Center. 111th General Meeting American Society for Microbiology. May 21-24,2011. New Orleans, LA. Interpretive Summary:
Technical Abstract: Background: Infections with A. baumannii-calcoaceticus complex (ABC) have complicated the care of combat casualties, and the spread and global dissemination of imipenem resistant (IR) clones of ABC have been reported in recent years. However, the epidemiological features of the IR-ABCs in military treatment facilities (MTFs) have not been thoroughly studied. Methods: In this study, 319 ABC repository strains isolated from US service members engaged in Iraq and hospitalized in different domestic and European MTFs from 2003 through 2009 were characterized genotypically and phenotypically to identify related bacteria. Results: Pulse-field gel electrophoresis (PFGE) revealed 61 PFGE types (PFTs) based on > 90% similarity. Eighty percent of the isolates belonged to 20 major and minor PFTs. Antimicrobial susceptibility tests (AST) revealed 50 (16%) IR-ABC isolates. Microarray analysis of 12 representative isolates indicated that only those that hybridized with a probe for blaOXA23-like gene were resistant to imipenem. PCR results showed that 49 of the IR-ABC isolates carried a gene related to blaOXA23 and 1 strain to a gene related to blaOXA-58. IR-ABC strains tended to cluster in association with isolation date and location. One cluster (PFT7) belonged to the European clone II group. Southern blots demonstrated that the blaOXA23 gene is either plasmid borne, chromosomal or both. Conclusion: Molecular characterization by PFGE, DNA microarray, Southern blot and PCR combined with classical susceptibility testing provided the precise information on imipenem resistance in this group of ABC strains. The distribution of IR-ABC clones implied nosocomial dissemination in the MTFs. The information from this study will benefit the development of rapid diagnosis, epidemiologic surveillance, empirical treatment and implementation of preventive strategies for IR-ABC infections in both military and civilian health care setting.