Antibacterial Effects of Peganum harmala Seed Extracts on Drug-resistant Clinical Isolates of Acinetobacter baumannii in North of Iran

 Acinetobacter baumannii is one of the most common and important causes of hospital-acquired infections. Due to its intrinsic resistance to antibiotics, A. baumannii can survive in the hospital environment for a long time and target hospitalized patients. Therefore, treatment and prevention of hospital-acquired infection with these bacteria require identification of new antibacterial agents with no or fewer side effects and toxicity.

 The aim of this study was to investigate and compare the antibacterial effects of the aqueous and ethanolic extracts of Peganum harmala on multidrug-resistant, extensively drug-resistant and pandrug-resistant Acinetobacter baumannii isolates.

 Antimicrobial susceptibility of the isolates was determined using the Kirby-Bauer method according to the Clinical and Laboratory Standards Institute document M100-S25 (2015). Antimicrobial activity of the ethanolic and aqueous extracts of P. harmala against drug-resistant A. baumannii isolates was determined by the agar well diffusion method. In addition, broth microdilution susceptibility testing was carried out to determine the minimum inhibitory concentrations (MICs) of the extracts. Finally, active compounds with antimicrobial activity were identified by gas chromatography-mass spectrometry.

 The frequencies of the multidrug-resistant, extensively drug-resistant and pandrug-resistant A. baumannii isolates were 37.2%, 58.2% and 61%, respectively. The MIC90 of the aqueous extract of P. harmala was 1024 μg/mL, which was four times less than that of its ethanolic extract (4096 μg/mL). Similarly, the MIC50 of the aqueous extract of P. harmala was significantly smaller than that of the ethanolic extract (P < 0.05). According to the results, vasicine/peganine and 8-hydroxy deoxy peganine were the most abundant (39.94%) bioactive compounds in the aqueous extract of P. harmala.

 The aqueous extract of P. harmala had excellent antimicrobial effects on the resistant A. baumannii isolates.