Antibacterial activity of plant essential oils against indigenously characterized methicillin-resistant Staphylococcus aureus (MRSA)

Plant essential oils were evaluated for antimicrobial activity against Methicillin-resistant Staphylococcus aureus (MRSA). The isolates (n=03) were procured from Institute of Microbiology, UVAS Lahore, Pakistan. After biochemical and 16S rRNA gene-based PCR characterization, accession numbers were retrieved from NCBI i.e. MW344063.1, MW344064.1 and MW344065.1. These isolates exhibited molecular positivity by multiplex PCR for mecA, coa and eta toxin genes. Moreover, these isolates exhibited resistance to cefoxitin, ampicillin, amoxicillin, penicillin, amoxicillin clavulanate, ciprofloxacin, erythromycin and gentamicin. The antibiotic resistant isolates were evaluated for antimicrobial activity of plant essential oils. The highest zone of inhibition (mean ZOI +/- S.D.) was measured for Cinnamomum verum (22.67 +/- 1.52 mm) followed by Eucalyptus globulus (18.67 +/- 2.51 mm) and Syzygium aromaticum (12.67 +/- 2.51 mm). Lowest mean MIC value (0.33 +/- 0.11 mg/mL) was recorded for E. globulus. Eucalyptus globulus was processed for fractionation by column chromatography and n-hexane, chloroform, n-hexane + chloroform and ethyl-acetate fractions were evaluated for antibacterial activity. Lowest mean MIC (10.04 +/- 5.80 mg/mL) was recorded for E. globulus n-hexane fraction. Cell survival percentage of BHK21 cell line was 51.7% at 54.87mg/mL concentration of E. globulus n-hexane fraction. Through gas chromatography-mass spectrometry (GC-MS) analysis of n-hexane fraction, benzene was found abundant (29.9%) as active compound. It was concluded that E. globulus n-hexane fraction exhibited significantly promising results against MRSA.