Sj. Gebran et al., A RAPID COLORIMETRIC ASSAY FOR EVALUATING LEGIONELLA-PNEUMOPHILA GROWTH IN MACROPHAGES IN-VITRO, Journal of clinical microbiology, 32(1), 1994, pp. 127-130
A rapid colorimetric technique for in vitro quantitation of Legionella
pneumophila intracellular proliferation in macrophages is described.
The assay is based on the electron transport activity of metabolically
active L. pneumophila. The yellow tetrazolium salt (4,5-dimethylthiaz
ol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) is cleaved by the mitoc
hondrial activity of viable L. pneumophila, forming a dark formazan de
rivative with an absorption spectrum different from that of the native
compound. The MTT method for measuring intracellular growth of L. pne
umophila closely correlated with the CFU assay. The ability of macroph
ages from the A/J mouse strain to support intracellular growth of L. p
neumophila and the ability of desferrioxamine to restrict L. pneumophi
la intracellular proliferation were confirmed by both methods. The MTT
assay offers the advantages of rapidity, simplicity, and cost efficie
ncy over the CFU assay, since it can be performed in the same flat-bot
tom microtiter plate with measurement in an enzyme-linked immunosorben
t assay reader, allowing efficient processing of large numbers of samp
les.