Pattisapu R. J. Gangadharam

Differential effects of free and liposome encapsulated amikacin on the survival of Mycobacterium avium complex in mouse peritoneal macrophages

Liposome-encapsulated amikacin shows significantly greater inhibitory activity against the survival of Mycobacterium avium complex inside mouse peritoneal macrophages than the free drug. Similar results were obtained whether the drug was added simultaneously with, 48 h prior to, or 48 h after the addition of mycobacteria to the macrophages. These observations support the hypothesis that the in vivo intravenous delivery of liposome-encapsulated amikacin results in the localization of the antibiotic in phagosomes containing mycobacteria inside resident macrophages of the liver and spleen.

Low-density poly(dl-lactide-co-glycolide) foams for prolonged release of isoniazid

Incorporation of the antitubercular drug isoniazid, INH, into low density poly(dl-lactide-co-glycolide), PLGA, foams of high interstitial void volume prior to high pressure extrusion is shown to prolong the in vitro release of INH. In vitro studies indicate that the duration of INH release can be significantly increased, the early burst dramatically reduced, and variation in replicate samples reduced. Control of the specific gravity and interstitial void volume of the foam is achieved by lyophilization of frozen polymer solutions of specified concentration. The morphology of foams prepared by lyophilization of glacial acetic acid solutions of the polymers produces leaflet or platelet structures. Matrices were prepared by (1) extruding INH impregnated foams previously compacted and ground to 125–180 microns, (2) directly extruding impregnated foams without prior compaction and grinding, and (3) extruding mechanically mixed micronized INH and ground PLGA which had not been prepared as foam. INH release kinetics, analyzed in terms of the Roseman-Higuchi model, confirms that release is diffusion controlled. Diffusion constants for the three methods are 1.2( ±0.1) × 10−4, 2.1(±0.3) × 10−4, and 3.2(± 1.6) × 10−4 cm2/day.

The beige mouse model for mycobacterium avium complex (MAC) disease: Optimal conditions for the host and parasite

We extended our earlier studies to establish the beige (C57B1/6/bgJ/bgJ) mouse model for experimental acute infections with Mycobacterium avium complex (MAC). Optimal conditions of the host and the parasites have been determined. Mice bred at our center showed similar responses to those obtained from Jackson Laboratories, the original supplier. Both male and female mice showed similar responses, but older mice in both sexes showed less susceptibility than younger mice. Strain 101 of MAC showed remarkable consistency in its pathogenicity to beige mice, as evidenced by the distribution of colony forming unit (CFU) counts at various time points after intravenous challenge, in several experiments. CFU counts showed an association with the dose of challenge, and histopathological observations.

Virulence of Mycobacterium avium complex strains from acquired immune deficiency syndrome patients: relationship with characteristics of the parasite and host☆

The virulence of 24 strains of Mycobacterium avium complex (MAC) isolated from patients with acquired immune deficiency syndrome (AIDS) was assessed using the beige mouse model. Most changes in colony forming unit (cfu) counts in spleen and lungs, and spleen weights occurred between days 1 and 14, with comparatively smaller changes 14-28 days postinfection. The virulence was assessed by a score formulated from the four most useful parameters: mortality, spleen cfu, lung cfu and spleen weights at 28 days. The scores of the 24 strains showed a normal distribution; four strains falling above one standard deviation from the mean were classified as high virulent, those four falling below one standard deviation as low virulent, and the remaining 16 as of intermediate virulence. Virulence was associated with the total number of plasmids and the occurrence of large plasmids (greater than 100 MDa) in the MAC strains. There was an inverse correlation between virulence and the organisms capacity to trigger the release of oxygen metabolites from peritoneal macrophages. Macrophages from mice infected with the MAC strains of different degrees of virulence released superoxide anion (O2-) with a peak at two weeks, the peak levels bearing an inverse correlation to virulence. No association was seen between virulence and source of specimens, biochemical characteristics, drug susceptibility, serotypes or phage types.

Release of isoniazid for prolonged periods from a biodegradable polymer under several in vitro and simulated in vivo conditions and in animals

Abstract Earlier studies by us have shown that a single subcutaneous implant of isoniazid in polylactic coglycolic acid (PLGA) polymer showed sustained levels of drug release for prolonged periods. These levels are comparable to those attained following daily oral administration of the drug. We have shown that by such administration, high in vivo chemotherapeutic activity, similar to that achieved by daily oral administration, was seen. Parallel to these studies we assessed the release pattern of the drug from the polymer in vitro, in simulated in vivo conditions and in experimental animals, using chemical methods for drug analysis and polarization, scanning and transmission electron microscopy techniques for implant characterization. These investigations have shown sustained release of isoniazid from a PLGA matrix in aqueous medium under several storage conditions. Polarization microscopy has verified the stability of the drug for the prolonged periods of release. Scanning electron microscopy has been helpful in observing the three-dimensional structural changes that occur in the polymer/drug matrix that occur during the in vivo drug release.

Identification of mycobacteria by smear examination of the culture

Mycobacteria can be tentatively identified by the arrangement of the bacilli on smears made from the growth and stained by the Ziehl-Neelsen method. The basis of this method is the presence or absence of cords with or without loose bacilli around. Agreement of a high degree (92.7% to 97.0%) was obtained between the identification of mycobacteria by this smear technique and by the niacin test. It is recommended that this simple procedure may be used for preliminary identification, especially in developing countries.

Antituberculosis activity of 6 cyclo-octylamino-5,8-oquinolinequinone (CQQ)

A new compound, 6 cyclo-octylamino-5,8-quinolinequinone (CQQ), a dual analogue of vitamin K and coenzyme Q, was effective against several drug-susceptible and drug-resistant strains of Mycobacterium tuberculosis. In vitro studies indicated the bactericidal nature of its action at 1 microgram/ml. Pulse exposure studies using M. tuberculosis H37Rv showed that a growth lag period of 96 hours resulted with exposure to 1 microgram/ml for 24 hours or longer.

Incorporation of Active Agent into Biodegradable Cement

The utility of bone cements has been recognized since 1951, when Charney first anchored an endoprosthesis with a self-curing polymethylmethacrylate (PMMA) cement (1). Acrylic bone cements currently available in the United States include Palacos RTM (Kulzer, FRG), Zimmer Bone CementTM and Zimmer Low Viscosity CementTM (Zimmer), CMW Type ITM (CMW, Blackpool, UK), and Surgical Simplex PTM (Howmedica). As an example of cement composition, the Surgical Simplex P is formulated to contain a mixture of PMMA and a copolymer of methylmethacrylate (MMA) and styrene. MMA monomer is used in the curing process, with benzoyl peroxide (BP) as initiator, N,N-dimethyl-p-toluidine(DMPT) as an accelerator to enable low temperature cure, and hydroquinone to inhibit premature polymerization.