The main objective of this study was to decipher the molecular mechanism of resistance to carbapenems and aminoglycosides in a large series of 150 Acinetobacter baumannii clinical isolates collected from July 2012 to September 2013 in Egypt. We report for the first time the emergence of bla NDM-1 and the cooccurrence of 16S rRNA methylase armA with bla NDM-1 and bla OXA-23 in Egyptian hospitals. Multilocus sequence typing identified 27 distinct sequence types, 11 of which were novel. Carbapenem and aminoglycoside resistance in Acinetobacter baumannii is considered an emerging, serious public health problem (1-3). The aim of the present study was to decipher the molecular support of resistance to carbapenems and aminoglycosides among 150 nonrepetitive A. baumannii clinical isolates collected from different clinical samples from inpatients at MabaretEl-Alasafra hospital (Alexandria, Egypt), El-Demerdash hospital (Cairo, Egypt), and the National Cancer Institute (Cairo, Egypt) from July 2012 to September 2013. Identification was performed using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) (4) and confirmed via PCR amplification and sequencing of the intrinsic bla OXA-51 -like gene (5). Antimicrobial susceptibility was determined using a modified Kirby-Bauer disk diffusion method. MICs were determined using Vitek 2 and confirmed for imipenem and amikacin by using Etest strips. Carbapenemase activity was detected phenotypically using the modified Hodge test (MHT) (6) and the modified Carba NP test (7) and confirmed by MALDI-TOF Ultraflex I mass spectrometry (8), while metallo-␤-lactamase activity was detected using the imipenem-EDTA combined-disk test (IECT) (9). All primers and probes used in this study for PCR amplification and sequencing are given in Table S1 in the supplemental material. Genetic mapping of carbapenemases (bla NDM-1 and bla OXA-23 -like), aminoglycoside-modifying enzyme (AME)-encoding resistance genes, and armA was performed for 20 selected isolates. Genotyping was done by multilocus sequence typing (MLST) (10). All isolates revealed a high degree of multidrug resistance (MDR) as shown in Fig. S1 in the supplemental material. Interestingly, 30/150 (20%) isolates were falsely identified as amikacin susceptible by Vitek 2, while they were identified as resistant by Etest (Fig. S1) as already reported (11). Overall, 131 out of 150 isolates (87.3%) were resistant to imipenem, with MICs of Ͼ16 g/ml. Among them, 125 isolates (95.4%) were MHT positive, and 59/150 isolates (39.3%) were IECT positive. In Egypt, there have been few reports describing the emergence of the bla OXA-23 gene among A. baumannii isolates (12-14) and one report of an NDM-2 carbapenemase isolate from a patient transferred to Germany from an Egyptian hospital (15). Herein, we found that 115/ 150 (76.7%) isolates were bla OXA-23 -like positive and 150/150 (100%) were bla OXA51 -like positive. The bla NDM-1 gene was not previously identified as playing a major role in carbapenem resistance...