Resistance of Aspergillus niger Tiegh. to the effect of amide anesthetics

The wide distribution of Aspergillus in nature is determined by their ability to adapt in the conditions of development of anthropogenic biocoenoses. Micromycetes survive due to rapid growth, intensive reproduction and labile metabolism, causing various kinds of damage to the substrates on which they were due to certain circumstances. However, it is noted that in the process of adaptation, many Aspergillus change physiologically, i.e. without changing the genetic information and heredity of this organism. These features of Aspergillus make them indispensable in model experiments allowing to assess the effects of xenobiotics even in micro doses and the ability to adapt to them. In this regard, it is interesting to investigate anesthetics widely used in surgery. Some of them have shown antibacterial activity, but their antifungal activity remains unknown. The authors investigated the ability of Aspergillus niger Tiegh. to adapt to the effects of certain amide anesthetics: lidocaine, ropivacaine and bupivacaine. Two series of experiments were carried out. In the first one the effect of anesthetics was investigated at concentrations of 0,001; 0,01 and 0,1 mg/ml per growth, number of colonies and sizes of spores and conidiophores; in the second one A. niger Tiegh. spores from a culture grown in a environment containing an anesthetic solution at a concentration of 0,001 mg/ml were germinated on nutrient medium with anesthetics at a concentration of 1 mg/ml. It was discovered that anesthetics affect differently the germination of spores and the formation of colonies of A. niger Tiegh. The maximum toxicity was shown by ropivacaine, significantly reducing the number of colonies, the minimum – by bupivacaine. It was discovered that ropivacaine and bupivacaine inhibit mycelium growth more than lidocaine. All investigated anesthetics at selected concentrations do not affect reliably the size of spores and conidiophores. The study of preadaptation caused by a low dose of anesthetics showed that the number of colonies in preadapted cultures after exposure at a high dose of 1 mg/ml significantly increased compared to direct exposure at a dose of 1 mg/ml. It can be argued that the observed changes in the number of colonies are an adaptive response of A. niger Tiegh. to the action of anesthetics. The diameter of colonies after preadaptation was significantly less than with direct exposure at a dose of 1 mg/ml (p < 0,05), that is we observe the effect of cumulation. Possible mechanisms of the observed effect, including hormesis, are discussed.