Submitted to: Interscience Conference on Antimicrobial Agents & Chemotherapy Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/12/2009
Publication Date: 9/12/2009
Citation: Huang, X.Z., Frye, J.G., Babel, B., Myers, T., Whitman, T., Barber, M., Lindler, L.E., Bowden, R.A., Nikolich, M.P. 2009. Molecular characteristics of Multidrug Resistant Acinetobacter baumannii Isolates from US soldiers from Iraq at the National Naval Medical Center. Interscience Conference on Antimicrobial Agents & Chemotherapy Proceedings. September 12-15,2009. San Francisco, CA. Interpretive Summary:
Technical Abstract: Background: Infections with A. baumannii-calcoaceticus complex (ABC) have complicated the care of combat casualties. The majority of A. baumannii isolates cultured from injured personnel from OIF and OEF have been multi drug resistant (MDR). Therefore, the genes causing MDR and genotypes related to MDR must be investigated. Methods: 116 A. baumannii isolated from wounded soldiers from Iraq treated at NNMC were characterized by Pulse Field Gel Electrophoresis (PFGE). DNA of representative isolates from each major PFGE cluster was analyzed with a DNA microarray designed to detect 775 antimicrobial resistance (AR) genes found in the NCBI database. MIC to antimicrobials was also determined for these isolates. The oxa27 gene, encoding a class D beta-lactamases associated with carbapenem resistance was assayed for by PCR of the 116 A. baumannii isolates. Results: 7 PFGE clusters with over 90% similarity were identified by UPGAMA and dice clustering method. 78% (90/116) of the isolates fell into the 7 clusters respectively while those remaining shared limited similarity with any other isolates. DNA microarrays of 8 representative isolates had positive hybridizations with 34 aminoglycoside, 8 Beta-lactamase, and 22 other genes (heavy metal, sulfonamide, tetracycline and genetic transfer related). MIC tests confirmed that only isolates with oxa27 were resistant to imipenem. PCR data showed 24 of the 116 isolates (21%) being oxa27 gene positive. Among those oxa27 positive isolates, 9 isolates are from PFGE cluster I and 12 from PFGE cluster IV. Conclusion: Combining molecular characteristic approaches such as PFGE, DNA microarray and PCR with classical MIC test will provide precise MDR information, which may benefit diagnosis, surveillance and development of preventive strategies for MDR ABC.