Background & Aims : Most of the methicillin resistant S.aureus isolates are resistant to many other antibiotics as well, so they can cause refractory infections. Therefore monitoring and control of these resistant isolates is always a necessity. Phosphomycin is an extended-spectrum antibiotic that inhibits synthesis of bacterial cell wall peptidoglycan and is helpful for controlling methicillin resistant S.aureus infections. However, because of bacteria’s ability of resisting to antibiotics and adaption and survival in antibiotic-containing environments, studies for finding of natural antibacterial compounds for treatment of such infections is essential Antibacterial effects of thymus vulgaris on Methicillin resistant S.aureus has already been shown. In this study the in vitro effects of phosphomycin along with thymus vulgaris essential oil on methicillin resistant S.aureus isolates were investigated.

  Materials & Methods : Forty six Methicillin resistant S.aureus isolates from clinical specimens were obtained . Minimum inhibitory concentration and minimum bactericidal concentration of phosphomycin was determined by serial dilutions of antibiotic in broth with concentrations ranging between 0.25-125 mg/L for each isolate. Also minimum bactericidal concentration of essential oil was obtained by adding 10-0.078 V/V of it in broth medium. The effect of antibiotic along with essential oil was measured by adding different concentrations of essential oil in Mueller-Hinton broth medium in the presence of sub-MBC doses of antibiotic then by adding 1/5 × 10⁶ CFU of each isolate and incubating test tubes overnight in 37° C. Minimum inhibitory concentration of phosphomycin along with thyme essential oil was determined for each isolate .

  Results : Out of 46 isolates of methicillin-resistant S.aureus , 15 % were sensitive to all investigated concentrations of phosphmycin and 2% were resistant, in total 43.5% of isolates were considered as resistant and 56.5% as sensitive. Isolates were sensitive to different concentrations of thyme essential oil. Synergism has been observed in 97.4 % of isolates between phosphomycin and thyme essential oil , in respect of their antibacterial effects.

  Conclusion : Regarding to the antimicrobial effects of thyme essential oil and synergistic effect of it with phosphomycin on most of the methicillin resistant isolates, more investigations for using this combination as an effective antimicrobial agent at least in topical antimicrobialgents formulations is advised. 

  SOURCE: URMIA MED J 2015: 26(5): 387 ISSN: 1027-3727