Formulation and efficacy of liposome-encapsulated antibiotics for therapy of intracellular Mycobacterium avium infection

Abstract

Mycobacterium avium is an intracellular pathogen that can invade and multiply within macrophages of the reticuloendothelial system. Current therapy is not highly effective. Particulate drug carriers that are targeted to the reticuloendothelial system may provide a means to deliver antibiotics more efficiently to M. aviuminfected cells. We investigated the formulation of the antibiotics ciprofloxacin and azithromycin in liposomes and tested their antibacterial activities in vitro against M. avium residing within J774, a murine macrophagelike cell line. A conventional passive-entrapment method yielded an encapsulation efficiency of 9% for ciprofloxacin and because of aggregation mediated by the cationic drug, was useful only with liposomes containing <50 mol% negatively charged phospholipid. In contrast, ciprofloxacin was encapsulated with >90% efficiency, regardless of the content of negatively charged lipids, by a remote-loading technique that utilized both pH and potential gradients to drive drug into preformed liposomes. Both the cellular accumulation and the antimycobacterial activity of ciprofloxacin increased in proportion to the liposome negative charge; the maximal enhancement of potency was 43-fold in liposomes of distearoylphosphatidylglycerol-cholesterol (DSPG-Chol) (10:5). Azithromycin liposomes were prepared as a freeze-dried preparation to avoid chemical instability during storage, and drug could be incorporated at 33 mol% (with respect to phospholipid). Azithromycin also showed enhanced antimycobacterial effect in liposomes, and the potency increased in parallel to the moles percent of negatively charged lipids; azithromycin in DSPG-Chol (10:5) liposomes inhibited intracellular M. avium growth 41-fold more effectively than did free azithromycin. Thus, ciprofloxacin or azithromycin encapsulated in stable liposomes having substantial negative surface charge is superior to nonencapsulated drug in inhibition of M. avium growth within cultured macrophages and may provide more effective therapy of M. avium infections.Mycobacterium avium infection is a common complication in AIDS (10, 38). For specimens taken from AIDS patients, M. avium could be cultured from 23 to 50% of blood cultures (37). M. avium can invade macrophages of the reticuloendothelial system (39), and intracellular organisms are able to withstand or evade macrophage antibacterial mechanisms. Furthermore, intracellular bacteria are shielded by the host cell from both immune surveillance and extracellular antibiotics.For effective therapy of M. avium infection, drugs must penetrate the host cells in cytostatic or cytotoxic concentrations. However, many antibiotics lack the ability to traverse the cell membrane, are excluded from acidic compartments such as the phagocytic apparatus, or are severely toxic when administered in the high doses necessary to overcome their low cellular permeability (19,36). To maximize the antimycobacterial effects of antibiotics while minimizing their toxicity, drug carriers to target drugs to M. avium-infected c...

Present status of nanoparticle research for treatment of Tuberculosis

“…A dose-related reduction in bacterial load was observed, but no sterilization was found [42]. Similar results were reported in literature for second-line antibiotics liposomes [43][44][45] [46]. Drug-loaded nanocarriers showed a significant decrease in the toxic effects when evaluated for cytotoxicity in peritoneal macrophages compared to free drugs.…”

Drug delivery systems for potential treatment of intracellular bacterial infections

“…Azithromycin-and ciprofloxacin-containing liposomes presented 40-fold greater activity in murine macrophages harboring Mycobacterium avium (64). Among the different ciprofloxacin formulations tested, a maximal cellular accumulation and antimycobacterial activity of ciprofloxacin was reached as the negative charge of the liposomes increased.…”

A New Era of Pulmonary Delivery of Nano-antimicrobial Therapeutics to Treat Chronic Pulmonary Infections

“…Mycobacterium avium 43-fold greater potency was seen against M.avium compared to free ciprofloxacin due to increased negative charge imparted by the liposome formulation of DSPG: Chol [117,155] CF-cystic fibrosis, TB-tuberculosis, DPI-dry powder inhalation, DSPG-distearoylphosphatidyl glycerol, DCP-dicetyl phosphate, HSPC-hydrogenated soy phosphatidylcholine, Egg PC-egg phosphatidylcholine, Chol-cholesterol, MAN-mannose, CFUs-colony forming units a suitable liquid, with deposition governed by the size characteristics of the nebulized droplets, or incorporated into larger carrier particles [157]. Microparticles are used as an alternative to liposomes, being more readily stable on storage or in the biological fluids, and they offer the possibility of modulation of release rate [158].…”