Abstract

The aim of the present study is to determine the activities of three kinds of antibiotics against Staphylococcal biofilm and planktonic cultures in vitro, and to indicate the enhancement of biofilm formation in response to stress factors such as glucose and sub-inhibitory concentrations of antibiotics by using scanning electron microscope. Biofilm forming staphylococci were identified by using the modified microtiter plate method. And the effect of different concentrations of several antibiotics (including ciprofloxacin, gentamycin and amoxicillin-clavulanic acid) on eight isolates was determined. The result showed that out of 86Staphylococcal isolates, eight strains were found to be strong biofilm forming. Sub-MIC of the antimicrobial agents used increased the biofilm formation in some isolates. However, the preformed biofilm was very difficult to remove with most isolates even with multiples of the MIC. The biofilm MBC reached 46 times the planktonic MBC in some isolates. Scanning electron micrographs of staphylococcus aureus isolate (45S) were made in order to confirm the enhanced biofilm formation in the presence of glucose and sub-MIC of ciprofloxacin and it was found that the slime layer production increases in the presence of glucose and low concentration of ciprofloxacin.

Key words: Staphylococcal biofilms, scanning electron micrograph, antimicrobial sub-MIC activity