We also assayed the strains for the presence of mutations in the quinolone resistance–determining regions (QRDRs) of gyrA gene encoding GyrA subunit of DNA gyrase and parC gene encoding ParC subunit of topoisomerase IV. We prospectively collected 121 consecutive single-patient MDR A. baumannii clinical strains during 2006 and 2007 at Cedars-Sinai Medical Center. We considered
a strain as MDR if it was resistant to two or more antibiotic classes that included anti-pseudomonal penicillin and its combination with β-lactamase inhibitor (e.g. piperacillin/tazobactam), anti-pseudomonal cephalosporins (e.g. ceftazidime or cefepime), carbapenems (e.g. IMP), aminoglycosides [e.g. tobramycin or amikacin (AN)], and fluoroquinolones (e.g. ciprofloxacin or levofloxacin) Fostamatinib based on VITEK® http://www.selleckchem.com/products/ch5424802.html 2 (bioMérieux, Inc.). All 121 strains were analyzed by repetitive PCR (rep-PCR) amplification using the DiversiLab®Acinetobacter Fingerprinting Kit according to manufacturer’s instructions
(bioMérieux, Inc.). Briefly, bacterial DNA was extracted using UltraClean™ Microbial DNA Isolation Kit (MO BIO Laboratories, Inc.). Amplification reactions were performed in the GeneAmp® PCR System 9700 under the following conditions: 2 min at 94 °C, 35 cycles of denaturation (30 s at 94 °C), annealing (30 s at 50 °C) and extension (90 s at 70 °C), and a final extension http://www.selleck.co.jp/products/CAL-101.html of 3 min at 70 °C. Rep-PCR products were separated by electrophoresis using the Agilent 2100 Bioanalyzer (Agilent Technologies, Inc.). Band patterns for each strain
were aligned and interpreted with web-based DiversiLab software provided by the manufacturer (bioMérieux, Inc.). Strains were grouped by ≥ 95% similarity. Medical record review identified an incident episode of nosocomial acquisition according to Centers for Disease Control surveillance definitions (Horan et al., 2008). Accordingly, 19 strains from patients with evidence of infection or colonization with A. baumannii prior to or at the time of admission to our institution during the study period were considered as having either a repeat episode or non-nosocomial A. baumannii infection, respectively, and their clinical strains were excluded from this study. Of the remaining strains, those belonging to the two prevalent clones, A and B, were selected for further analyses. Etest (bioMérieux, Inc.) was performed on 33 representative strains that were resistant to at least three classes of antibiotics (26 of clone A and seven of clone B) for susceptibility to IMP, COL, AN, DOX, tigecycline (TGC), RIF, and azithromycin (AZT) as per manufacturer’s recommendations.