Detection of adeABC efllux pump encoding genes and antimicrobial effect of Mentha longifolia and Menthol on MICs of imipenem and ciprofloxacin in clinical isolates of Acinetobacter baumannii

BackgroundAcinetobacter baumanniiis an opportunistic pathogen that causes nosocomial infections especially in patients in intensive care units (ICUs). Accordingly, the aim of our study was to detectionof adeABCefllux pump encoding genes and antimicrobial effect of the essential oil ofMentha longifoliaandMentholon the minimum inhibitory concentration (MIC) of imipenem and ciprofloxacin in clinical isolates ofA. baumannii.MethodsA total of 75 clinical isolates ofA. baumanniiwere collected. The presence of efflux pump genes was detected by polymerase chain reaction (PCR). The minimum inhibitory concentration (MIC) of the essential oil ofMentha longifoliaand Menthol and their combined effect with antibiotics were measured by microbroth dilution method and fractional inhibitory concentration (FIC) index.ResultsThe frequency ofadeA,adeB, andadeCgenes in clinical isolates ofA. baumanniiwere 86.7, 90.7, and 92%, respectively. When the essential oil ofMentha longifoliawas combined with ciprofloxacin and imipenem, MICs decreased 4- and 8-fold, respectively. In the combination of menthol with imipenem, the resistance to imipenem was reduced from 0- to 16-fold in 90% (63/70) of the isolates.ConclusionThe presence of efflux pump genes in more than 90% ofA. baumanniiisolates indicates its potential role in inducing imipenem- and ciprofloxacin-resistance in this bacterium. Menthol has an antimicrobial effect as an active ingredient inMentha longifolia. In the future, the combination of medicinal plants with antibiotics can be used as a complement in treating diseases caused by drug-resistant bacteria such asA. baumanniiinfections.