We investigated antibiotic resistance levels among bla NDM -positive (n = 9) and -negative (n = 65) A. baumannii clinical isolates collected in 2010 and 2015 from Alexandria Main University Hospital, Egypt using disc diffusion and minimum inhibitory concentration (MIC) determination. Plasmids from bla NDM -positive isolates were transformed into a carbapenem-susceptible A. baumannii (CS-AB) isolate to assess the role of plasmid transfer in mediating carbapenem resistance. Imipenem, meropenem, and ertapenem MIC90 values against bla NDM -positive isolates were 128, > 256, and 256 µg/mL, respectively. Plasmid isolation and polymerase chain reaction revealed that bla NDM was plasmid mediated. The plasmids were electroporated into the cells of a CS-AB isolate at an efficiency of 1.3 × 10-8 to 2.6 × 10-7, transforming them to bla NDM -positive carbapenem-resistant cells with an imipenem MIC increase of 256-fold. In addition to carbapenem resistance, the bla NDM -positive isolates also exhibited higher levels of cephalosporins, tetracycline, aminoglycosides, fluoroquinolones, and colistin resistance than the bla NDM -negative isolates. Acquisition of bla NDM -carrying plasmids dramatically increased imipenem resistance among A. baumannii isolates. Intriguingly, bla NDM -positive isolates also showed a high degree of resistance to antibiotics of different classes. The potential co-existence of different resistance determinants on A. baumannii plasmids and their possible transfer owing to the natural competence of the pathogen are especially alarming. More effective infection control and antibiotic stewardship programs are needed to curb the spread and treat such infections in both hospital and community settings.
Keywords: Antimicrobial resistance; Imipenem; Metallo-beta-lactamases; Transformation.
© King Abdulaziz City for Science and Technology 2020.