[The effect of liposomes on the growth and sensitivity of Mycobacterium smegmatis to isoniazide].

The effects of the liposome form of isoniazide (IN) and liposomes without IN on the growth of Mycobacterium smegmatis were studied. Fluorescent assay demonstrated that the fraction of liposomes that interacted with M. smegmatis amounted to 1-3%. It was shown that the IN efficiency in a liposomal form decreased depending on the liposome composition and concentration as compared with the IN in water solution. A preincubation of mycobacteria with liposomes led to a decrease in their sensitivity to IN. An analogous effect was observed when incubating M. smegmatis with oleic acid. It was postulated that the relative resistance of M. smegmatis to the antibiotic when using lipids as a carbon substrate appeared due to a change in the agent's metabolism and should be taken into account when testing in vitro the liposomal forms of antibiotics.

[Role of carbon substrates of culture media on Mycobacterium smegmatis susceptibility to antitubercular agents].

Influence of medium composition on Mycobacterium smegmatis growth and susceptibility to antituberculosis drugs (ATD)--isoniazid and rifabutin--was studied. It was shown that addition of phospholipids (PL) in form of liposomes to meat peptone broth resulted in activation of M. smegmatis growth and decrease of its susceptibility to ATD. Growth characteristics of M. smegmatis and its susceptibility to ATD were studied using variants of modified on source of carbon synthetic medium Sauton as growth substrate. It was revealed that presence of acetate or PL in growth medium results in significant decrease of M. smegmatis susceptibility to isoniazid and rifabutin. It was suggested that this phenomenon is determined by activation of glyoxylate cycle by PL and fatty acids, which, in its turn, can stimulate expression of a number of proteins, including cell membrane pumps excreting antibiotics out of microbial cell.