AGUEOUS-ETHANOLIC MEDICINAL PLANT EXTRACTS CAN RESTORE ERYTHROMYCIN SENSITIVITY OF SKIN STRAINS OF STAPHYLOCOCCI WITH RIBOSOMAL MECHANISM OF MLS-RESISTANCE

Skin isolates of S. aureus and S. epidermidis strains were tested for susceptibility to antibiotics of MLS-group by disk diffusion test. 7 strains with inducible phenotype of MLS-resistance based on ribosomal 23S-rRNA modification have been used in this investigation. Antimicrobial concentrations of plant extracts and erythromycin (ERY) were determined by two-fold serial dilution in nutrient agar. Synergistic effects of plant extracts and ERY dual combinations were assessed using the checkerboard assay against tested strains. Alnus incana L. fruits extract was the most potent inhibitor of staphylococci growth (MIC 40.625-162.5 µg/mL); while Geranium pratense L. rhizomes extract exhibited the least antimicrobial activity (MIC 650-2,600 µg/mL). Alnus incana L. fruits and Geranium pratense L. rhizomes extracts showed strong synergy with ERY against 100% strains of staphylococci (average FICI 0.028 – 0.057; p<0.001). In the presence of 1/4 MIC of ERY was registred 32-64-fold reduction of Alnus incana L. fruits extract MIC and 64-256-fold reduction of Geranium pratense L. rhizomes extract MIC. Aqueous-ethanolic extracts of Betula verrucosa L. buds (average FICI 0.473±0.20), Arctostaphylos uva-ursi (L.) Spreng. leaves (average FICI 0.143±0.18) and Tamarix ramosissima Ledeb. leaves (average FICI 0.189±0.29) showed synergic interaction with ERY against 71.4-85.7% tested strains. Sanguisorba officinalis L. root extract showed non-interactive effect with ERY against 42.8%, additive interaction against 28.6% and synergic action against 28.6% strains of staphylococci (average FICI 0.812±0.52). isolates of staphylococci. Biota orientalis (L.) Endl. (Platycladus orientalis (L.) Franco) fruits and Cotinus coggygria Scop. (Rhus cotinus R.) leaves extracts exhibited non-interactive effect with ERY against all tested strains (average FICI 2.0±0.0). Experimental data indicate that combination of plant extracts with macrolides in therapeutic regimens against MLS-resistant staphylococci is promising, particularly for the treatment of pyoderma.