In vitro Study on the antibacterial Activity of Selected Iraqi Medicinal Plants against Multi Drug Resistant Clinical Isolates

Abstract

The solutions to this are more sought after by the emergence of the multi-drug resistant (MDR) bacteria. The paper tested the MDR clinical isolates (n=5 total: MRSA, ESBL-producing E. coli, P. aeruginosa, carbapenem-resistant K. pneumoniae, and A. baumannii) on the antibacterial activity of methanol and aqueous extracts of five Iraqi medicinal plants ( Thymus vulgaris, Nigella sativa, Matricaria chamomilla, Rosmarinus officinalis and Punica granatum ). The minimum inhibitory and minimum bactericidal concentration were established using broth microdilution technique according to CLSI guidelines (M07-A10). Thymus vulgaris methanolic extract had the highest antibacterial activity with MIC values of 3.12-12.5 mg/mL and MBC values of 6.25-25 mg/mL (MBC /MIC ratio 1-2, which indicates bactericidal activity). Nigella sativa was also found to be very active against MRSA (MIC 6.25mg/mL, MBC 12.5mg/mL). The Punica granatum peel extract showed a broad-spectrum activity (MIC 6.25-25mg/mL). Thymol (42.3) and carvacrol (28.6) were found to be major constituents of T. vulgaris by gas chromatography-mass spectrometry (GC-MS) analysis, with NIST 17 library. These results believe in the possibilities of the Iraqi medicinal plants as sources of natural antibacterial agents, but the MIC values are quite high compared to conventional antibiotics (normally <0.001 mg/mL) which implies their use as complements and not as alternatives to conventional antimicrobial treatment.