New in vitro model of Mycobacterium tuberculosis dormancy

<b>Background:</b> M. tuberculosis (<i>Mtb</i>) is able to persist in the body of persons with LTBI in dormant state becoming resistant to anti-TB drugs. In culture models induction of the dormant <i>Mtb</i> phenotype was shown to be under the influence of various factors; the main sign of <i>Mtb</i> dormancy is reversible loss of the ability to grow on culture media (Batyrshina, Ya, et al. Tuberculosis 2019; 117:7-17). <b>Aim:</b> To evaluate the effect of nutrient deprivation in <i>Mtb</i> culture as a potential inducer of dormant phenotype of <i>Mtb</i>. <b>Methods:</b> We cultured <i>Mtb</i> H₃₇Rv strain in Middlebrook 7H9 media from which albumin, dextrose, sodium chloride, and catalase were excluded during 30 days. Optical density (OD₆₀₀) and colony forming unit (CFU) values were determined daily for evaluation of <i>Mtb</i> growth ability. <i>Mtb</i> resuscitation ability was evaluated after abrogation of deprivation by adding the above-mentioned components into growth medium. <b>Results:</b> The delay of growth in nutrient-deprived medium was observed beginning from the 2nd day of <i>Mtb</i> incubation, as assayed by OD₆₀₀ values. CFU values (on the agar Middlebrook 7H10) was decreased by 1-1,5 log by 2-3 days of incubation. After 4 days of deprivation <i>Mtb</i> completely lost their replicative ability. Abrogation of deprivation resulted in the recovery of the <i>Mtb</i> replicative capacity on the solid and liquid media after 5-17 and 5-11 days, respectively. <b>Conclusions:</b> Culture of <i>Mtb</i> under conditions of deprivation of the above-mentioned components results in the induction of <i>Mtb</i> with phenotypical signs of dormant state. This method of induction of dormant phenotype of <i>Mtb</i> may be used as new in vitro model to study <i>Mtb</i> dormancy phenomenon including susceptibility testing of dormant form of <i>Mtb</i> to anti-TB drugs.