الفهرس 
Literature ReviewOnly 14 pages are availabe for public view
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Abstract
Acinetobacter baumannii is one of the pathogens responsible for healthcare associated infections (nosocomial).
A. baumannii were collected from different compartments or inanimate objects of different public hospital in Cairo. Out of 117 isolates only 78 isolates (66.6%) were suspected as A. baumannii based on the morphological and biochemical characteristics, and then identified using the API NE20.
Pattern of antimicrobial resistance was studied using the simple disk diffusion technique. According to the antibiotic susceptibility test, results showed that the confirmed A. baumannii isolates were highly resistant. Eleven out of 78 (14.1% ) were detected as PDR.
The 11 selected bacterial isolates of PDRs
A. baumannii were molecularly identified using 16S rDNA sequencing technique, and were deposited to NCBI and were listed and documented. They were recorded under accession No.ON797630 to ON797640. The phylogenetic tree was constructed from the identified 16S rDNA bacterial sequences with their respective reference sequences from GenBank.
The phosphoethanolamine-lipid A transferase MCR-1 gene that responsible for the resistance to colistin was detected in ten out of 11 selected strains of
A. baumannii that had not been previously observed to carry MCR-1 gene. Nucleotide sequence of MCR-1 genes has been uploaded to NCBI and was listed and documented under accession No. LC754315. It was similar to the nucleotide sequence encoding phosphoethanolamine- lipid A transferase MCR-1 in Escherichia coli strain L36 (MT070408).
The minimum inhibitory concentration (MIC) assays were used to identify the synergism between anionic antibiotics and colistin against colistin-resistant strains 78 and 90. Additionally, it is used to identify synergism between natural compound pterostilbene and colistin against colistin-resistant strains. The study showed that MCR-1-expressing A. baumannii can alter the colistin resistance in the presence of a range of anionic antibiotics that are typically active against Gram-positive bacteria. Moreover, the micro dilution method of pterostilbene combined with colistin can restore the bactericidal activity of colistin against MCR-1-positive A. baumannii.
Finally, the transmission electron microscope photos proved the synergistic effect of combination of colistin with
anionic antibiotic and the combination with pterostilbene on outer membrane. The combination could alter the permeability properties by the disruption of A. baumannii membrane, which then leads to the death of bacterial cells.