Antimicrobial activity of selected non-antibiotics--activity of methotrexate against Staphylococcus aureus strains

Some non-antibiotic drugs, e.g. cytostatics, anaesthetics or vasodilators may also show the antimicrobial activity. The aim of this study was to detect and characterise the antimicrobial activity expressed by selected non-antibiotic drugs analysed during state control performed in the Drug Institute. Over 60 drugs were randomly chosen from different groups. The surveillance study was performed on standard microbial strains: S. aureus ATCC 6538P, E. coli ATCC 8739, P. aeruginosa ATCC 15442 and C. albicans ATCC 10231. It was found that the drugs listed below inhibited growth at least one of the examined strains: Acesan 0.075 tabl., Benuron 500 mg tabl., Chlorchex 0.5 aerosol, Methotrexat-Ebewe 500 mg amp., Naproxen 500 mg tabl., Nospa Forte 60 mg tabl., Platamine 50 mg amp., Platidiam 50 mg amp., Sensit 50 mg drag., Septofervex 2 mg tabl., Seractil 400 mg tabl., Sermion 4 mg amp., Sinemet 125 mg tabl., Tarproxen 500 mg tabl. and Zyban 150 mg tabl. It was interesting, that strong antimicrobial activity of methotrexate was limited to Staphylococcus aureus strain. Minimal inhibitory concentration of methotrexate was determined by agar dilution method with the use of 54 clinical S. aureus strains (MRSA-32 and MSSA-22). For MSSA strains, MIC50 and MIC90 were 10 micrograms/ml and 20 micrograms/ml, respectively (range: 10-20 micrograms/ml). For MRSA strains, MIC50 and MIC90 were 20 micrograms/ml and 100-> 100 micrograms/ml, respectively (range: 10-< 100 micrograms/ml).