American scientists have proposed* a new system for delivering bacteriophages—viruses that attack bacteria—to the lungs. The system could help treat chronic pneumonia caused by antibiotic-resistant pathogens.

Phage therapy is a promising alternative to antibiotics in the treatment of bacterial infections. Bacteriophages are highly specific agents that attack only target bacteria, do not harm the body's normal microflora, and do not contribute to the development of drug resistance in pathogens. However, there are still many challenges associated with the clinical use of phages, particularly their delivery to certain organs, particularly the lungs.

A team of scientists from the Georgia Institute of Technology (USA) has presented a new method for delivering phage preparations to the lower respiratory tract using special carriers. These are dry, porous polymer microparticles onto which phages are coated and inhaled into the lungs. Previously, scientists attempted to deliver phage aerosols into the lungs using a nebulizer, but this method proved ineffective. Using these microparticles, an inhaler for delivering phage preparations to the lungs could be created. A unique feature of these carrier microparticles is that phages adsorbed to them remain active. The microparticles are small enough to penetrate deep into the lungs, but large enough to withstand immediate elimination. The microparticle material biodegrades within a few days.

To coat microparticles with phages, they are simply immersed in a phage preparation and then dried. In this form, the phages remain active for two weeks at room temperature and quickly activate when inhaled into the lungs.

A new method of delivering phage preparations has enabled treatment of mice with pneumonia. Furthermore, a significant reduction in bacterial populations was achieved in experiments on transgenic mice whose lung conditions resemble those of cystic fibrosis. Chronic pneumonia, most often caused by antibiotic-resistant strains of Pseudomonas aeruginosa , is a major problem in this disease.

This is not the first time that phage preparations have been tried in cystic fibrosis, and the proposed method has so far demonstrated good results. When delivered on microparticles, phages are also capable of destroying the biofilms formed by bacteria.

Scientists are now planning further trials of the phage delivery method to the lungs in larger animals, particularly against chronic infections relevant to patients with cystic fibrosis.

* Agarwal R, Johnson CT, Imhoff BR, Donlan RM, et al. Inhaled bacteriophage-loaded polymeric microparticles ameliorate acute lung infections // Nature Biomedical Engineering, Published: July 16, 2018. DOI: 10.1038/s41551-018-0263-5