Synergistic and antagonistic action of antibiotics against biofilm forming Staphylococcus aureus

12 Clinical isolates of Staphylococcus aureus from various specimens of infectious bodily sites having ability of biofilm formation were screen in this study. On the basis of their ability to attach to polymeric surfaces, the formation of biofilm was determined in 6 wild type clinical isolates. Minimum biofilm inhibitory concentration (MBIC) of seven antibiotics (ampicillin, azithromycin, ciprofloxacin, erythromycin, gentamycin, oflaxicin, and penicillin) was estimated against the established biofilm on polystyrene microtiter plates. Biofilms were observed to be less susceptible to antibiotics by comparing the MBIC with MIC. The synergism result was investigated by the comparison of MBIC and FBIC. Synergy was demonstrated against the combination of beta lactam antibiotics (ampicillin + penicillin and ampicillin + cloxacillin) and their combination with macrolide antibiotics (ampicillin + azithromycin and penicillin + azithromycin). The observed values of partial synergistic, indifferent and antagonistic result were 12.5%, 16.67% and 55.55% respectively.

Author(s): Neha Singh* and Neeraj Mishra

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