Susceptibility Patterns in <em>Staphylococcus </em>and <em>Klebsiella </em>Causing Nosocomial Infections upon Treatment with E-Anethole-Rich Essential oil from <em>Clausena anisate</em>

High rates of resistance to antibiotics are associated with healthcare-related infections, thus appealing for the urgent need for effective antimicrobials against these maladies. The present study aims to determine the chemical composition of essential oil (EO) from Clausena anisata leaves, and evaluate their antibacterial activity against selected nosocomial bacteria. Fresh leaves of Clausena anisata were subjected to a steam distillation using a Clevenger apparatus to afford the essential oil. The phytochemical composition of this oil was analyzed using gas chromatography-mass spectrometry (GC-MS). The essential oil was further tested against selected nosocomial bacteria, including Staphylococcus and Klebsiella species, among others, using a microdilution method. As a result, 0.77% of essential oil was extracted from fresh leaves of Clausena anisata. The GC-MS analysis revealed that the as-prepared essential oil contain E-anethole (70.77%), methyl isoeugenol (13.85%), estragole (4.10%), &gamma;-terpinene (3.33%), myrcene (2.82%) and sabinene (0.77%), with E-anethole being the major constituent. Meanwhile, twenty two compounds were identified in the EO of Clausena anisata leaves through gas chromatography. Upon antibacterial test against selected nosocomial pathogens, the E-anethole-rich essential oil exhibited minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values ranging from 3.91 to 125 &micro;g/mL and 7.81 to 125 &micro;g/mL, respectively, indicative of a bactericidal orientation of the plant&rsquo;s essential oil (MIC/MBC ratio: 4). This novel contribution highlights the scientific validation of the use of Clausena anisata leaves in the traditional treatment of various infectious diseases. However, toxicity and pharmacokinetic studies, mechanistic basis of the antibacterial action, and in vivo antibacterial experiments of the E-anethole-rich essential oil of Clausena anisata should be investigated to successfully use this plant in the treatment of infectious diseases.