Background: Acinetobacter baumannii is an opportunistic pathogen that causes nosocomial infections especially in patients in intensive care units (ICUs). Accordingly, the aim of our study was to detection of adeABC efllux pump encoding genes and antimicrobial effect of the essential oil of Mentha longifolia and Menthol on the minimum inhibitory concentration (MIC) of imipenem and ciprofloxacin in clinical isolates of A. baumannii. Methods: A total of 75 clinical isolates of A. baumannii were collected. The presence of efflux pump genes was detected by polymerase chain reaction (PCR). The minimum inhibitory concentration (MIC) of the essential oil of Mentha longifolia and Menthol and their combined effect with antibiotics were measured by microbroth dilution method and fractional inhibitory concentration (FIC) index. Results: The frequency of adeA, adeB, and adeC genes in clinical isolates of A. baumannii were 86.7, 90.7, and 92%, respectively. When the essential oil of Mentha longifolia was 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. Conclusion: The presence of efflux pump genes in more than 90% of A. baumannii isolates indicates its potential role in inducing imipenem-and ciprofloxacin-resistance in this bacterium. Menthol has an antimicrobial effect as an active ingredient in Mentha 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 as A. baumannii infections.

Background: Acinetobacter baumannii is one of the causes of nosocomial infections, especially in the intensive care unit. The emergence of multidrug-resistant strains of A. baumannii has caused many problems. One of the ways to handle the phenomenon of antibiotic resistance is the use of herbal medicines and their derivatives in place of or in combination with antibiotics. The aim of this study was to investigate the effect of inhibitory effects of berberine as a barberry derivative on clinical isolates of A. baumannii, resistant to ciprofloxacin and imipenem in Hamadan hospitals. Materials & Methods: In this study, 70 clinical isolates of A. baumannii. were identified and diagnosed using conventional microbiology. Resistance of isolates was detected against imipenem and ciprofloxacin by disk diffusion and broth microdilution method. Minimum inhibitory concentration (MIC) of berberine as well as its combined effect with antibiotics were performed using broth microdilution method. Results: The results of this study showed that more than 90% of isolates are resistant to ciprofloxacin and imipenem. Imipenem and ciprofloxacin MICs were dtermined from 8 to 28 and 4 to 32 μg / mL, respectively. The berberine decreased the imipenem and ciprofloxacin MIC from zero to two fold and zero to one-fold, respectively. Conclusion: High level resistance to imipenem and ciprofloxacin among A.baumannii isolates is cause of concern. Berberin, in combination with imipenem and ciprofloxacin, reduces MIC to a proper level, which can be used as an effective agent to reduce antibiotic resistance in bacteria.