Leili Shokoohizadeh - Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
Shirin Moradkhani - Department of Pharmacognosy , Faculty of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran
Mohammad Yousef Alikhani - Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
Nayreh Zare Fahim - Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
Hassan Mahmoudi - Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran

Introduction and objectives: Acinetobacter baumannii is an opportunistic pathogens that cause nosocomial infections especially in patients in intensive care units (ICU). Accordingly, the aim of our study was investigation on inhibitory effect of the essential oil of Mentha Longifolia and menthol on Ade ABC efflux pumps in ciprofloxacin and imipenem resistance clinical isolates of A. baumannii. Materials and Methods: A total of 75 clinical isolates of A. baumannii were collected. The presences of efflux pump genes were detected by Polymerase Chain Reaction (PCR). Minimum Inhibitory Concentration (MIC) of the essential oil of Mentha Longifolia and Menthol and their combined effect with antibiotics were measured by microbroth dilution and Fractional Inhibitory Concentration (FIC) index. Results: The frequency of ade A, ade B and ade C genes in clinical isolates of A. baumannii were 93.3%, 96%, and 97.3%, respectively. When the essential oil of Mentha longifolia with ciprofloxacin and imipenem were combined, MICs decreased 4 and 8 fold, respectively. In menthol combination with imipenem, in 90 %( 63/70) of the isolates the resistance to imipenem reduced from 0 to 16 folds. Conclusion: The presence of efflux pump genes, in more than 90% of A.baumannii isolates, indicates the potential role of efflux pump in inducing imipenem and ciprofloxacin resistance in this bacterium. Menthol has an antimicrobial effect as an effective ingredient in Mentha Longifolia. In the future, the combination of medicinal plants with antibiotics can be used as a complement to treat diseases caused by drug-resistant bacteria such as A.baumannii infections.

Acinetobacter baumannii, Efflux Pump, Menthol, Mentha Longifolia