and indicated the latter as the most accurate way of assessing the antimicrobial effect. The microdilution method with TTC (2,3,5-triphenyl tetrazolium chloride)
or INT (2-p-iodophenyl-3-pnitrophenyl-5-phenyl tetrazolium chloride) to indicate the viability of aerobic bacteria was found to be the best alternative approach,
while only ATP determination was appropriate for microaerophilic
Campylobacter spp.
Using survival curves the kinetics of bacterial inactivation on plant extract exposure
was followed for 24 h and in this way the MIC values determined by the microdilution method were confirmed as the concentrations of extracts that inhibited bacterial growth.
We suggest evaluation of the antibacterial activity of plant extracts using the broth microdilution method as a fast screening method for MIC determination and the macrodilution method at selected MIC values to confirm bacterial inactivation.
Campylobacter spp. showed a similar sensitivity to plant extracts as the tested gram-positive bacteria, but S. Infantis and E. coli O157:H7 were more resistant.