smaller concentrations of natural products (more sensitive). Under definite conditions, results using both variants of bioautographic method showed good reproducibility proving good precision of the assay.
In the present study, if we compare results listed in Tables 2 and 8 (referred to 0.5 mg extracts assayed by both screening tests) and consider 9 mm diameter as breakpoint for implying active extracts (18)(diffusion method criteria) then we can notice that six extracts tested showed to be active against S. aureus by diffusion method and seven extracts by bioautographic method. Nevertheless, if we consider diffusion method well variant and bioautographic method direct variant, as parameters for comparison, we can observe that the same six extracts were active by the first method while only five extracts were active by second method. Therefore, according to results, there was no significant difference between the employed methods.
As indicated in Table 10, there was no difference among results yielded by both culture mediums. MHB medium is still used in our laboratory because of its fast and easy preparation. In order to assure fidelity of the obtained results, tests are read by two methodologies: optical density measurement (ELISA reader) and colorimetric assay for detection of bacterial growth (INT). These combined procedures were adopted because ELISA methodology allows successive determination of minimum bactericidal concentration (MBC) values and colorimetric assay allows confirmation of ELISA reader results in case of testing a not completely vehicle-soluble or colorful compound.