Inhibitory activity of Mentha spicata oils on biofilms of Proteus mirabilis isolated from burns

Abstract

Introduction and Aim: Proteus mirabilis is an opportunistic pathogen, infecting humans, through the release of endotoxins and enzymes such as urease, hemolysin, protease, DNase etc. One of the factors contributing to its virulence is its unusual ability to form crystalline biofilms. This study aimed to investigate the effect of Mentha spicata volatile oil on P. mirabilis biofilm formation.   Materials and Methods: P. mirabilis was isolated from infected wound of burns of patients using conventional biochemical tests. Vitek 2-Compact System was used to confirm the diagnosis of bacterial isolates. The isolates were tested for their susceptibility to 11 antibiotics. Aqueous and alcoholic extracts as well as Volatile Oil and natural Menthol extracted from M. spicata were tested for their ability to inhibit biofilm formation by P. mirabilis.   Results: In this study 16 out of the 45 burn injury samples were tested positive for P. mirabilis.  Bacterial isolates were found to be resistant to the drugs Levofloxacin and Norfloxacin, with percentages of 10.2% and 11.8%, respectively. Majority of these isolates had the capacity to produce several virulence factors, including biofilm in variable amounts and the enzymes protease, hemolysin, DNase, and gelatinase. The volatile oil and natural component menthol extracted from M. spicata inhibited the formation of biofilm at increasing concentrations.   Conclusion: The volatile oil and the natural menthol compound of M. spicata are effective in inhibiting biofilm formation by P. mirabilis.