Introduction: The use of antimicrobial properties of medicinal plants can solve common problems in the use of antibiotics. The aim of this study was to evaluate the antibacterial properties of the Mentha longifolia essence on bacteria isolated from hospital infections.
 
Materials & methods: In this experimental study the Mentha longifolia essence was extracted using Clevenger device and its antimicrobial activity agar disk diffusion method for determination of bacterial sensitivity and dilution method for determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was used separately.
 
Findings: The results of bacterial sensitivity test in the case of the standard antibiotics of tetracycline, amikacine, and also disks impregnated with Mentha longifolia essence showed that the diameter of the zone of inhibition caused by the compound being tested on four strains of isolates was far larger and this difference about Escherichia coli and Klebsiella isolates was significant (p<0.05). Also the results of MIC and MBC tests indicated that the inhibition of bacterial growth by Mentha longifolia essence had a direct relationship with the amount of available Mentha longifolia essence in the dilution and increasing of Mentha longifolia essence in each dilution reduced the number of cultured bacterial colonies and no bacterial growth was observed in the dilution equivalent to MBC of Mentha longifolia essence.
 
Discussion & conclusions: The results suggest that Mentha longifolia essence can be used as a source of cheap and accessible replacing chemical drugs to treat some bacterial infections.