The suitability of selected humic acid batches as culture media additives for isolating thermophilic Campylobacter species

Using freshly poured respectively five days under light and air stored Campylobacter media blood or lignite humic acids containing Mueller-Hinton-Agar proved to be better for isolation of a Campylobacter field strain than unsupplemented or peat humic acids containing media. The observed differences between the used media are probably caused by three different ability to prevent the accumulation of a photochemically induced toxicity by storing of media under light and air. The storage of blood respectively lignite humic acids containing media over fourteen days under dark and air leads to a time and trend dependent decrease of the colony counts of the Campylobacter field strain. By means of equations of spline functions the observed decrease in ability of media to support the growth of thermophilic Campylobacter can be described mathematically. By using the mathematical model the theoretical extend of growth of Campylobacter on the media can be determinate with respect to the applied inoculum and to the time of storage of media. The cause of decrease in the isolations rate with respect to the time of storage and the cause of different effectiveness of the used humic acids in the media are discussed.