A preliminary study on the effect of nicotine on growth of mycobacteria

LJ medium is routinely used in the laboratories for the growth of tubercle bacilli. Addition of aqueous extract of tobacco (5 mg/ml) revealed enhancing effect on the growth of slow-growing mycobacteria. Addition of pure nicotine in LJ media in different concentrations ranging from 500 μg/ml to 10 μg/ml stimulated the growth of standard strains of M. tuberculosis H₃₇ RV, M. kansasii, M. scrofulaceum, M. avium and M. intracellulare in vitro. Visible colonies developed within 8-9 days in LJ media and became confluent by 10-12 days. The control LJ media without nicotine showed luxuriant growth by 3 weeks of incubation or later. This effect was confirmed repeatedly. A comparative study on the efficiency of conventional LJ medium and nicotine LJ medium in the isolation of M. tuberculosis from sputum specimens was also carried out. The isolation of positive cultures was higher in nicotine LJ medium. Growth on nicotine LJ medium was significantly faster. Addition of nicotine in a concentration of 500 μg/ml stimulated the growth and helped in the early isolation of M. tuberculosis from sputum specimens of patients suffering from pulmonary tuberculosis. Niacin-negative Afro-Asian variants of M. tuberculosis when grown on nicotine-LJ medium, could convert themselves into niacin proders. Detection of niacin production is an important test in the identification of M. tuberculosis and the problem of identification of these producers. strains in the laboratory due to weak or no niacin production could be solved by growing them in nicotine incorporated LJ medium. The possibility of nicotine acting as an inducer substrate for the enzyme responsible for niacin production is discussed.