An in vitro test using cholesterol metabolism of macrophages to determine drug sensitivity and resistance of Mycobacterium leprae

Macrophages that have ingested live Mycobacterium leprae show a preferential accumulation of cholesterol ester. Such an accumulation is not seen, on the ingestion of dead bacteria. Among the macrophages that ingest live Mycobacterium leprae, the presence of dapsone or rifampicin prevents largely the alteration in the anticipated increase in the cholesterol ester indicating the sensitivity of the bacteria to the drug. In the small number of relapsed patients, the presence of dapsone did not reduce the cholesterol ester increase, suggesting that the Mycobacterium leprae present are either resistant or escaped detection. The method provides a rapid drug screening system foranti-Mycobacterium leprae activity of known and unknown compound

Mycobacterium leprae mediated stimulation of macrophages from leprosy patients and hydrogen peroxide production

Macrophages cultured from the peripheral blood of normal individuals, tuberculoid leprosy patients and long-term-treated, bacteriologically negative lepromatous leprosy patients are able to release hydrogen peroxide on stimulation withMycobacterium leprae. Macrophages from lepromatous leprosy patients who are bacteriologically positive produce considerably lower levels of hydrogen peroxide, even though stimulation of these cells withMycobacterium leprae is definitely demonstrable. This differential stimulation of macrophages appears to be largely specific toMycobacterium leprae. There is also a good indication that decreased stimulation of macrophages from positive patients could be due to an after-effect of infection. It is possible that while other factors aid survival ofMycobacterium leprae in the macrophages, hydrogen peroxide may not be as effective in the killing of the bacteria in infected patients as it would be, perhaps, in other infections

Relationship of the major constituents of the Neurospora crassa cell wall to wild-type and colonial morphology

Relationship of the major constituents of the Neurospora crassa cell wall to wild-type and colonial morphology. J. Bacteriol. 90:1073-1081. 1965.-The relationship of cell wall to morphology in Neurospora crassa was studied by correlating the levels of structural polymers of the cell wall with wild-type and colonial morphology. The cell wall of N. crassa contains at least four major complexes: a peptide-polysaccharide complex; two glucose polymers, one of which was found to be a laminarinlike β-1,3-glucan; and, lastly, chitin. The levels of one or more of these structural polymers are consistently altered in single-gene mutants with colonial growth, and in sorbose-induced colonial growth. The proportions of these polymers, particularly of the peptide-polysaccharide complex and the β-1,3-glucan, appear to be important to morphology

Cholesterol metobolism of macrophages in relation to the presence of Mycobacterium leprae

Macrophages phagocytose Mycobacterium leprae and live bacilli inside such macrophages alter the lipid metabolism. There is increased accumulation of cholesterol ester in the bacteria infected cells. This increase appears to be due to the decreased level of esterase enzyme that could hydrolyse cholesterol esters. Associated with decreased level of this enzyme is the reduced amount of protein synthesis. Increased cholesterol ester may be responsible for conversion of macrophages into foamy cells in the presence of M. leprae

In vitro drug screening system using membrane alteration in macrophages by Mycobacterium leprae

The observation that live Mycobacterium leprae on entry into macrophages from lepromatous leprosy patients reduced the number of EA rosetting macrophages, was extended to macrophages from Swiss white mice also. Further, the fact that dead Mycobacterium leprae do not bring about such a change in macrophages from mice, allowed us to develop this into a bacterial viability testing system. Thus drug treated macrophages in the presence of Mycobacterium leprae showed normal rosetting ability if Mycobacterium leprae are inactivated by the drug, but showed reduced level of rosetting when bacteria were not susceptible to the drug. It was shown that a drug like dapsone, does act on Mycobacterium leprae based on its permeability, quantity available inside the macrophages and inhibition of its action by Para amino benzoic acid. The inactivation of Mycobacterium leprae by sulphone and rifampicin was also proved by the flourescence diacetate method, which showed poorly viable bacteria after exposure to drugs. Thus it has been possible to develop a rapid drug screening method for testing the activity of unknown compound against Mycobacterium leprae

An in vitro system to study drug sensitivity of Mycobacterium leprae using infected human tissue

A reliable screening technique for assessing the sensitivity of Mycobacterium leprae to drugs has been developed. The method is based on the susceptibility or otherwise of M. leprae- infected tissues from lepromatous leprosy patients to the action of diaminodiphenyl sulphone (dapsone) or rifampicin on the incorporation of [14C]-acetate into lipids. The extent of inhibition or lack of inhibition correlated very well with the drug sensitivity or resistance of the bacteria isolated from the patients to the above drugs. A similar trend was observed when the incorporation into individual fractions of neutral lipids was measured. There was no incorporation by heat-killed tissues. This method correlates well with the 3,4-dihydroxyphenylalanine uptake studies