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Background: The recent emergence of multidrug resistance (MDR) in Acinetobacter baumannii (A. baumannii ) has raised concern in health care settings in Iraq. This is the first report of the whole genome sequence of A. baumannii ZQ isolated from Iraqi patients. To better comprehend the repertoire of MDR genetic elements and organization, we compared the genome sequences of eight extended drug-resistant (XDR) and two less drug-resistant A. baumannii ZQ strains with that of other completely sequenced A. baumannii from divergent worldwide distributed isolates.
Results: In consistence with their phenotypic antimicrobial resistance profiles, ZQ genomes harbors high to moderate numbers of genetic determinants, including β-lactamases, aminoglycoside-modifying enzymes, efflux pumps, modifications of target sites. Several strains showed nearly identical genome sequence, frequent structural variation was detected even between the closely related strains.
Conclusion: In general, the shorter the genetic distance among strains, the less insertion/deletion events proceed. However, frequent genomic changes was observed even inside the closely related strains of A. baumannii. Antimicrobial resistance genes are likely to be the target accumulating such variations, suggesting that the resistance elements respond actively to the selection pressure in the hospital setting. Besides the lateral acquisition of genetic material from resistant bacterial strains, the drastic issues is associated with continuous presence of intrinsic resistance genes in the genome of A. baumannii, which are ready to be boosted by exposure to sub-inhibitory levels of the antibiotics in the environment and might also play an important role in the evolution of resistance to the new derivatives of different antibiotic classes.
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