Abstract
Introduction: The continuous increasing in the emergence of antibiotic-resistance in pathogenic
bacteria has led to the development of new alternatives that are active against the pathogens. In Iraq,
many plant components have been extensive attention as alternative medicine. Materials and
Methods: Punica granatum, Mentha pulegium, Allium cepa, Allium sativum and Piper nigrum are five
Iraqi medicinal plants were studied in this study. The plant samples were extracted in by three types
of solvents, ethanol, methanol and hot boiled water. The plant extracts were examined as
antibacterial agents against both Staphylococcus epidermidis and Klebsiella pneumoniae in four
concentrations (50, 100, 150, 200 mg/ml) by using the agar-well diffusion method. Results: All
assayed plant extracts have antibacterial activity in different concentrations and this activity was
varied depending on some factors: the species of bacteria, the type of plant, the type of solvent and
the concentration of extract. Depending on the species of bacteria, Gram negative bacteria has higher
sensitivity than Gram positive against most studied plant extracts. The type of solvent has a clear
effectiveness on the antibacterial activity, the ethanolic extract has the highest antibacterial activity
of most studied plants, while the aqueous extract has the lowest activity. On the other hand, the
increasing of extract concentration has been associated with increasing of the diameter of inhibition
zone. Depending on the type of extracted plant, the maximum diameter of inhibition zone was yielded
from Punica granatum extract regardless with the type of the solvent.