Efficacy of engineering controls in reducing occupational exposure to aerosolized pentamidine.

Aerosolized pentamidine administration may pose potential risks to health care workers exposed to fugitive drug and to infectious respiratory pathogens (eg, tuberculosis) generated by pentamidine-induced cough. Classic infection control methods may be applied to this problem, although the effectiveness of these measures in mitigating environmental pentamidine exposure is unknown. Lack of data fully characterizing pentamidine's mechanism of action or potential mutagenicity, carcinogenicity, or teratogenicity raises concern and suggests worker exposed and environmental contamination be minimized. We report herein on the efficacy of an aerosol containment hood in containing fugitive pentamidine aerosol during administration.

Radiometric measurement of differential metabolism of fatty acid by mycobacteria.

An assay system has been developed based on automated radiometric quantification of 14CO2 produced through oxidation of [1-14C] fatty acids by mycobacteria. Two stains of M. tuberculosis (H37Rv and Erdman) and one of M. bovis (BCG) in 7H9 medium (ADC) with 1.0 microCi of one of the fatty acids (butyric, hexanoic, octanoic, decanoic, lauric, myristic, palmitic, stearic, oleic, linoleic and linolenic) were studied. Results previously published on M. lepraemurium (Hawaiian) were also included for comparison. Both strains of M. tuberculosis had maximum 14CO2 production from hexanoic acid. Oxidation of butyric and avid oxidation of lauric acids were also found with the H37Rv strain but not with Erdman. In contrast, 14CO2 production by M. bovis was greatest from lauric and somewhat less from decanoic acid. M. lepraemurium showed increasing oxidation rates from myristic, decanoic and lauric acids. Assimilation studies of M. tuberculosis H37Rv confirmed that most of the oxidized substrates were converted into by-products with no change in those from which no oxidation was found. These data suggest that the radiometric measurement of differential fatty acid metabolism may provide a basis of strain identification of the genus Mycobacterium.

Radiometric measurement of differential metabolism of fatty acids by Mycobacterium lepraemurium.

An assay system has been developed based on automated radiometric quantification of 14CO2 produced through oxidation of (1--14C) fatty acids by mycobacteria. With this system, the Hawaiian strain of M. lepraemurium was studied using the K-36 buffer as a suspending solution for the organisms along with 5.0 muCi of one of the following fatty acids: acetate, butyric, hexanoic, octanoic, decanoic, lauric, myristic, palmitic, stearic, oleic, linoleic, linolenic, and malonic. The 14CO2 production by this organism was greatest with lauric, decanoic, myristic, octanoic, stearic, oleic, linoleic, linolenic, and malonic. The 14CO2 production by this organism was greatest with lauric, decanoic, myristic, octanoic, and stearic acids, in decreasing order. Assimilation studies and radiochromatograms confirmed that most of the oxidized substrates were converted into by-products with no change in those from which no oxidation was found. These data suggest that the radiometric measurement of differential fatty acid metabolism may provide a basis of radiometric identification of M. lepraemurium and assessment of the growth requirements of this organism.

Histochemical studies relating the activation of macrophages to the intracellular destruction of tubercle bacilli.

Dermal tuberculous lesions, both primary and those of reinfection, were produced in rabbits with 14C-labeled BCG and biopsied once at various times. Macrophage activation was evaluated by the indolyl histochemical test for beta-galatosidase, the number of bacilli in macrophages by acid-fast staining, and the breakdown of bacilli by autoradiography. After the rabbits became tuberculin positive, the stongly activated macrophage population contained a) fewer parasitized cell, b) fewer bacilli in each parasitized cell, and c) more "free" 14C-label (not associated with intact bacilli) than the weakly activated macrophage population. These results suggest that the more highly activated macrophages had destroyed many of the bacilli that they once contained and that their power to do so was enhanced by immunologic mechanisms.

Radiometric studies of Mycobacterium lepraemurium.

The radiometric method has been applied for studying the metabolism of M. lepraemurium and the conditions which might force or inhibit its metabolic activity in vitro. These organisms assimilate and oxidize (U-14C) glycerol, and (U-14C) acetate, but are unable to oxidize (U-14C) glucose, (U-14C) pyruvate, (U-14C) glycine and 14C-formate. When incubated at 30 degrees C M. lepraemurium oxidizes (U-14C) acetate to 14CO2 faster than 37 degrees C. The smae effect was observed with increasing concentrations of polysorbate 80 (Tween 80), or the 14C-substrate. No change in metabolic rate was observed when the organisms were kept at -20 degrees C for 12 days. Although tried several times, it was not possible to demonstrate any "inhibitors" of bacterial metabolism in the reaction system. The radiometric method seems to be an important tool for studying metabolic pathways and the influence of physical and biochemical factors on the metabolism of M. lepraemurium in vitro.

A radiometric method for predicting effectiveness of chemotherapeutic agents in murine leprosy.

A simple radiometric method has been developed for evaluating the effect of drugs on the metabolism of M. lepraemurium. The method is based on the measurement of the 14CO2 produced through bacterial metabolism of acetate-U-14C. Seventeen drugs were tested: bacitracin, cephaloridine, chloramphenicol, cycloserine, dactinomycin, DDS, ethionamide, INH, kanamycin, methenamine mandelate, nitrofurantoin, oxacillin, polymyxin B, rifampicin, streptomycin, sulfadimethoxine and vancomycin. The drugs which caused most marked inhibition were chloramphenicol, INH, ethionamide and nitrofurantoin in order of increasing effectiveness. The radiometric study which is completed in 15 days permits direct study of the drug effect on the metabolism of M. lepraemurium and a more rapid screening of antileprosy drugs than has previously been possible. Currently, these observations are being extended to studies of the structure-activity relationships of antileprosy drugs and the metabolism and drug susceptibility of M. leprae in vitro.

Radiometric measurement of metabolic activity of Mycobacterium lepraemurium.

A sensitive and nondestructive radiometric method has been applied to the detection of metabolism of Mycobacterium lepraemurium, as a model for the study of the metabolism and substrate requirements of M. leprae. The method is based on the measurement of the (14)CO(2) produced through the bacterial conversion of [U-(14)C]acetate or [U-(14)C]glycerol by 7 x 10(9) bacteria suspended in 10 ml of either a simple buffer system (K-36) or a complex medium (NC-5). Metabolism of the bacilli was easily detected within 3 days after inoculation and was measured daily. NC-5 medium supported metabolism of M. lepraemurium for several weeks longer than the simple K-36 buffer. The radiometric technique shows promise as a rapid and efficient system for evaluating the metabolism of mycobacteria without introducing any changes in the physiologic state of the organisms, studying their metabolic pathways, determining conditions potentially favorable for multiplication of these organisms in vitro, and studying their susceptibility to inhibition by drugs.

Environmental control of glycogen and lipid content of Mycobacterium tuberculosis.

Nitrogen-limited cultures of the R(1)R(v) strain of Mycobacterium tuberculosis accumulate both glycogen and lipid as endogenous reserves. The carbon source in the medium regulates the extent of the storage material accumulation.

Differences in the utilization of glycerol and glucose by Mycobacterium phlei.

A basic difference was found in the kinetics of uptake and utilization of glucose and glycerol by washed suspensions of Mycobacterium phlei. With glucose, the rates of uptake, respiration, and assimilation were saturated at low external substrate concentration. With glycerol, these rates were found to increase with increasing substrate concentration and did not show saturation at any concentration tested. Qualitatively similar patterns were observed for cells grown on either glycerol or glucose. Above a saturation concentration, ratios of cell (14)C to CO(2) (14)C for uniformly labeled (14)C-glucose were constant at a value of 0.96. Glycerol-U-(14)C, on the other hand, yielded cell-(14)C/CO(2)-(14)C ratios which were highest at the lowest glycerol concentration tested, and decreased with increasing substrate concentration. The distribution of the glucose and glycerol carbons assimilated into M. phlei were qualitatively similar. Quantitatively, however, the uptake and assimilation of glycerol was far more rapid than that of glucose for all substrate concentrations employed. These quantitative differences in the utilization of glycerol and glucose could account for the increased content of nonessential lipid and polysaccharide found in glycerol-grown M. phlei.