en باکتری شناسی پزشکی Medical Bacteriology مقاله پژوهشی Original Research Article <p style="text-align: justify;"><span style="font-size:16px;"><span style="font-family:Times New Roman;"><b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Background and Aim:</span></span></span></b><span style="color:black">&nbsp;</span></span></span><span style="color:#000000;"><span style="font-size:16px;"><span style="font-family:Times New Roman;"><span style="line-height:150%">The growing prevalence of antibiotic-resistant oral pathogens has increased interest in medicinal plants as alternative sources of antimicrobial agents. <i>Melissa (M.) officinalis</i> L. (lemon balm) is rich in bioactive phytochemicals, particularly terpenoids, known for their antimicrobial potential. This study aimed to evaluate the antibacterial activity of <i>M. officinalis</i> extracts and isolated terpenoids against dental plaque&ndash;associated bacteria and to investigate their inhibitory mechanisms against penicillin-binding protein (PBP) and &beta;-lactamase using <i>in vitro</i> and <i>in silico </i>approaches.</span></span></span></span><br> <span style="font-size:16px;"><span style="font-family:Times New Roman;"><b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Materials and Methods:</span></span></span></b><span style="color:black"> </span></span></span><span style="color:#000000;"><span style="font-size:16px;"><span style="font-family:Times New Roman;"><span style="line-height:150%"><i>M. officinalis</i> extracts and terpenoids were tested against <i>Streptococcus viridans</i>, <i>Porphyromonas gingivalis</i>, <i>Prevotella intermedia</i>, and <i>Aggregatibacter actinomycetemcomitans</i>. Antibacterial efficacy was assessed using inhibition zone assay, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC), with amoxicillin as a reference drug. Molecular docking was conducted to analyze the binding interactions of ursolic acid and amoxicillin with consensus-modeled PBP and &beta;-lactamase proteins.</span></span></span></span><span style="font-size:16px;"><span style="font-family:Times New Roman;"><span style="color:black"> </span><br> <b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Results:</span></span></span></b><span style="color:black"> </span></span></span><span style="color:#000000;"><span style="font-size:16px;"><span style="font-family:Times New Roman;"><span style="line-height:150%">Both crude extracts and terpenoids exhibited strong antibacterial activity, producing large inhibition zones and low MIC and MBC values as compared to amoxicillin. <i>S. viridans</i> displayed greater resistance, with MIC and MBC values approximately twice those of other bacteria. Docking analysis demonstrated strong binding affinities and high specificity for terpenoids toward &beta;-lactamase and PBP, forming stable protein&ndash;ligand complexes.</span></span></span></span><br> <span style="font-size:16px;"><span style="font-family:Times New Roman;"><b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Conclusion:</span></span></span></b><span style="color:black">&nbsp;</span></span></span><span style="color:#000000;"><span style="font-size:16px;"><span style="font-family:Times New Roman;"><span style="line-height:150%"><i>M. officinalis</i> terpenoids represented promising natural inhibitors of PBP and &beta;-lactamase and may serve as alternative antimicrobial agents for controlling dental plaque&ndash;associated infections.</span></span></span></span></p> <p style="text-align: justify;"></p> β-lactamase, Dental Caries, Melissa officinalis, PBP, Terpenoids 6 6 http://ijmm.ir/browse.php?a_code=A-10-3006-1&slc_lang=en&sid=1 Gulbahar F. Karim kulbharkarim@uokirkuk.edu.iq 100319475328460033879 100319475328460033879 Yes Basic Science Department, College of Nursing, University of Kirkuk, Kirkuk, Iraq Ali Hasan Mohamed alibarzinjy@uokirkuk.edu.iq 100319475328460033880 100319475328460033880 No Department of Medical Laboratory Analysis, College of Health Science, Cihan University, Sulaimanya, Iraq Emad Ibrahem emad.ibrahem70@gmail.com 100319475328460033881 100319475328460033881 No Department of Medical Laboratory Analysis, College of Health Science, Cihan University, Sulaimanya, Iraq Omeed Omeed Darweesh od54@uoalkitab.edu.iq 100319475328460033882 100319475328460033882 No College of Pharmacy, Al-Kitab University, Kirkuk, Iraq Sarah Ahmed Hasan sarahahmed100@uokirkuk.edu.iq 100319475328460033883 100319475328460033883 No Basic Science Department, College of Nursing, University of Kirkuk, Kirkuk, Iraq