Background & Aims: 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.

SOURCE: URMIA MED J 2016: 27(1): 26 ISSN: 1027-3727