The Gram-negative bacteria have an outer membrane that serves as an impermeable
barrier for many small molecules. Our research is consistent with findings of other researchers so that most plant extracts have inhibition effect on Gram-positive and Gram-negative bacteria[19-25]. Several investigators studied the antimicrobial activity of essential oil of lemongrass plant against pathogenic bacterial strains and found that Enterococcus fecalis was the most sensitive microorganism, while P.aeruginosa was the most resistant[25-27].