Prevalence of ISAba1-blaOXA-23, ISAba125-blaNDM-1, and armA genes in High-Level Aminoglycoside Resistant Acinetobacter baumannii

Background: Acinetobacter baumannii is one of the most common pathogens causing health care associated infections that may result in serious morbidity and even may cause death in critical units like intensive care units, this is because of its intrinsic drug-resistance mechanisms in addition to acquired ones. Aminoglycosides, plays a crucial role in managing infections caused by gram negative bacilli. In case of A. baumannii, these groups face strong resistance mechanisms due to genes specially armA gene which is present in most of High level Aminoglycoside Resistant (HLAR) A. baumanni isolates. Successful combinations used to manage A. baumanni infection gather both carbapenems and aminoglycosides together, as they produce synergistic effects. Carbapenem resistance has become a major health problem, most commonly, Acinetobacter spp. mediate carbapenem resistance through production of carbapenemases that belong to OXA-type carbapenemase and metallo-β-lactamases (MBLs), including NDM-1. Insertion sequences located near carbapenemases genes in A. baumanii isolates can control their expression and mobility mostly through formation of transposon structure. Objectives: the aim of this work is to study the combination of resistance genes and to explore their insertion sequences. Methodology: In this study 65 A. baumanii isolates were obtained from ICUs of Zagazig University hospital and all were nosocomial infections. HLAR was determined among the isolated strains. Antibiotic susceptibility testing was performed. The presence of ISAba1, blaOXA-23, ISAba125, blaNDM-1, and armA genes was tested by polymerase chain reactions. Results: We found that 23 (35.4%) of A. baumanni isolates were HLAR, all were rersisant to both gentamicin and amikacin, and 19 (82.6.5%), &18 (78.3%) were resistant to imipenem and meropenem respectively. Resistence genes were isolated from all A. baumannii strains, as blaOXA-23, blaNDM-1, and armA, were found in (78.5%), (36.9%), (81.5%) respectively. Regarding the ISAba1, and ISAba125, they were found associated with blaOXA-23, and blaNDM-1, in (92.2%), and (83.3%) respectively. In HLAR armA gene was present in all 23 isolates, while blaOXA-23, and blaNDM-1 genes were present in (69.6%), and (73.9%). Fifteen (65.2%) HLAR isolates contain all of ISAba1/blaOXA-23, ISAba125/NDM-1, and armA genes. Conclusion: We found that a great percent of A.baumanni isolates carrying antibiotic resistant genes either alone or in combination and the presence of insertion sequences and carbsapenemase producing genes together with HLAR in the same isolates represent a serious health problem and predict a spread of more powerful strains which will result in a real critical situations specially that the number of effective antibiotics against these strains are continually decreasing.