APPLICATION OF THE COMBINED EFFECT OF PHOSPHOMYCIN AND ZATARIA MULTIFLORA ESSENTIAL OIL ON REDUCTION OF BIOFILM AMOUNTS PRODUCED BY P.AERUOGINOSA PAO1

Pseudomonas aeruginosa is a gram-negative bacterium which is capable of
producing biofilm, phosphomycin is one of the broad-spectrum antibiotics and Zataria multiflora is
among the most widely used medicinal plants. The aim of this study was to evaluate the combined
effects of Phosphomycin and Z.multiflora essential oil against biofilm formation by P. aeruginosa
PAO1.
Materials & Methods: Minimum inhibitory concentration (MIC) and Minimum bactericidal
concentration (MBC) of phosphomycin and Z.multiflora essential oil were determined in the
concentration range of 0.25- 128 mg and 0.078%- 10% v/v, respectively. The biofilm formation amounts
were measured in the absence of antimicrobials and then in the presence of sub-lethal concentrations of
them alone or in combination. Two-factor analysis of variance was used to assess the main effects of
Z.multiflora essential oil, antibiotic and the interaction between Z.multiflora essential oil and
phosphomycin.
Results: Minimum inhibitory and bactericidal concentrations of phosphomycin were 64 mg/mL and
minimum bactericidal concentration of the essential oil was 5%. The amount of biofilm formation in the
absence of phosphomycin and Z.multiflora essential oil was the most, but in the presence of
phosphomycin and sub-lethal concentration (2.5% V/V) of Z.multiflora essential oil was significantly
reduced. More reduction was observed in the presence of the both compounds. Statistical analysis
showed that there was a significant difference in biofilm formation in the presence of all phosphomycin
doses compared with its absence; however, there was no significant difference between the amounts of
biofilm formation in the presence of different concentrations of antibiotic (the difference between all
groups, p> 0.05).
Conclusion: Combined use of Z.multiflora essential oil and phosphomycin, especially in low
concentrations of phosphomycin, is a promising way to control and prevent biofilm formation by of P.
aeruginosa PAO1