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There is mounting evidence that Acinetobacter baumannii has a naturally occurring carbapenemase gene intrinsic in this species. Presence of class 1 integrase gene in Acinetobacter isolates is a useful marker for causing outbreaks in hospitals and for being epidemic strains of A. baumannii. The goal of the present study was to detect the resistance and outbreak marker genes by multiplex polymerase chain reaction (PCR) (blaOXA-51-like gene and class 1 integrase gene). Also to detect the correlation between imipenem susceptibility and detection of blaOXA-51-like gene. For these purposes, 51 consecutive, non-duplicate, A. baumanii strains were isolated from various clinical and environmental specimens from the Intensive Care Units (ICUs) of Assiut University Hospitals, Egypt. All the isolates were identified by conventional standard methods. The antibiotic sensitivity pattern was determined by Kirby Bauer disc diffusion method. For imipenem, the minimum inhibitory concentrations (MICs) were determined using Epsilometer (E test). Multiplex PCR was performed for the detection of the blaOXA-51-like and Class I integrase genes. The blaOXA-51-like gene was detected in (95.8%) and (96.3%) in clinical and environmental isolates, respectively. Class I integrase gene was detected in (75%) and (70.3%) in clinical and environmental isolates, respectively with statistically significant difference (P value of clinical samples = 0.041 and P value of environmental samples =0.011). This means that these strains have metallo-beta-lactamase (MBL) gene (cause outbreak in hospital at any time). Also (67.35%) of A. baumanii isolates are imipenem sensitive and positive for blaOXA-51-like gene and this means that these isolates contain hidden metallo beta lactamase MBL gene. Key words: Acinetobacter baumanii, blaOXA-51-like genes, Class I integrasegene, MBL gene.