Molecular Assessment of MCR-1 Gene among Pandrug-Resistant Acinetobacter baumannii

Background Antimicrobial resistance has become one of the most widespread threats to humans. Acinetobacter baumannii is one of the pathogens responsible for healthcare-associated infections (nosocomial). Colistin is considered the last resort antibiotic against infections with pandrug-resistant (PDR) pathogens. Results: Eleven isolates were detected phenotypically as PDR A. baumannii and were confirmed molecularly using 16S rDNA. The MCR-1 gene was not detected within the chromosomal DNA of the selected isolates. Plasmid bearing the MCR-1 gene was identified in 10 selected isolates of A. baumannii that had not been previously observed to carry the MCR-1 gene. Moreover, the use of colistin in combination with anionic antibiotics or natural compound pterostilbene poses a viable therapeutic alternative for PDR and revives colistin’s bactericidal effects on MCR-1-positive A. baumannii. Finally, the transmission electron microscopy studies proved the synergistic effect of these combinations and revealed the disruption of resistant A. baumannii’s outer membrane and alteration of the permeability properties that allowed overcoming the resistance of the isolates to colistin. Conclusions: Antimicrobial resistance of A. baumannii is related to the presence of the transferable plasmid-bearing MCR-1 gene. This study proved the ability of the combinations of colistin with anionic antibiotics and/or natural compound pterostilbene to restore the bactericidal effect of colistin. Overall, these combinations could be novel promising clinical alternatives against the increasing threat of the widespread multidrug-resistant A. baumannii.