Impact of Marjoram (Origanum marjorana L.) Essential Oil on Some Virulence Factors and DNA Integrity of Multidrug Resistant Klebsiella pneumoniae

Infectious diseases represent an important cause of morbidity and mortality among the populations, particularly in developing countries. Therefore, pharmaceutical companies have been motivated to develop new antimicrobial drugs in the recent years especially due to the constant emergence of microorganisms resistant to conventional antimicrobials. The current study aims to evaluate the antimicrobial efficacy of some essential oils (EOs) against multidrug resistant (MDR) K. pneumoniae. Antibiotic susceptibility profile of 15 K. pneumoniae isolates was performed against 14 antibiotics and 14 essential oils. The effect of the most potent EO against the chosen isolate regarding some virulence factors and DNA fragmentation was studied. Among all the tested antibacterial agents, MEO was the most effective one. Gas chromatography/mass spectrometry of MEO revealed that, terpinen-4-ol was the major constituent followed by γ-terpinene. Treatment using MEO led to a significant reduction in biofilm formation, complete killing within 4 hours, change in membrane permeability and reduction of capsular layer of the tested cells. Also, 2 MIC of MEO caused the highest damage of bacterial DNA. This study strongly suggests that MEO possesses antibacterial properties and induces DNA degradation. These results were correlated with chemical composition of the tested oil. Key Words; Antimicrobial resistance; Essential oils; Biofilm formation; DNA fragmentationn