A modified bioautographic method for antibacterial component screening against anaerobic and microaerophilic bacteria

Direct bioautography is a useful method to identify antimicrobial compounds with potential therapeutic importance. Because of technical limitations till now, it has been applied only for aerobic bacteria. In this work we present the modification of the original method by which antimicrobial screening of bacteria requiring modified atmosphere became feasible by direct bioautography. Here we demonstrate its applicability by testing three anaerobic Clostridium perfringens and three microaerophilic Campylobacter jejuni strains against two essential oils, clove and thyme. Antimicrobial component profiles of clove and thyme essential oils against these two medically important pathogenic bacteria were compared and significant differences were revealed in their inhibition capacities. Linalool, a component of thyme essential oil exerted a more expressed antibacterial activity against C. perfringens than against C. jejuni. Our results demonstrate that direct bioautography is not only suitable for testing aerobic bacteria, but by applying the presently described modified version it can also contribute to the quest to find novel antimicrobial agents against multidrug resistant anaerobic and microaerophilic bacteria.