In experiments on mice with acute pneumonia, treatment with specific bacteriophages was as effective as antibiotic therapy and was not associated with increased inflammation*

In bacterial pneumonia, lung function can be significantly impaired as a result of the pathogen's contact with the immunologically highly reactive pulmonary epithelium. In particular, excessive, uncontrolled inflammation is a key factor in the pathogenesis of respiratory distress syndrome, a life-threatening condition that can complicate the course of pneumonia.

Treatment of bacterial infections with bacteriophages has attracted particular interest worldwide in recent years due to the spread of antibiotic-resistant strains of pathogenic bacteria. Consequently, the impact of phage therapy on patients, particularly on the development of infectious inflammation, is being comprehensively studied.

In an experiment* conducted at the Pasteur Institute (France), mice with acute pneumonia caused by two strains of Escherichia coli (536 and LM33) received specific bacteriophages (536_P1 and LM33_P1) intranasally or antibiotics (ceftriaxone, cefoxitin, imipenem-cilastatin) intraperitoneally. A control group of healthy mice received bacteriophages. Early (≤ 12 h) and late (≥ 20 h) treatment outcomes were assessed: the degree of pulmonary edema, the level of proinflammatory cytokines in the blood and lung homogenate, a complete blood count, and the content of bacteria and bacteriophages in lung tissue.

Treatment results in the bacteriophage and antibiotic groups were similar, although bacteriophages reduced bacterial counts more quickly than antibiotics. Treatment with bacteriophages was not associated with excessive inflammation; instead, it reduced inflammation and was accompanied by a more rapid recovery of abnormal blood counts than in the antibiotic group.

In the control group, in the absence of bacteria, bacteriophage 536_P1 caused a slight increase in the production of antiviral cytokines and chemokines in the lungs, but not in the blood. However, this bacteriophage did not elicit a similar response in infected animals.

Thus, animal models have shown that rapid lysis of bacteria during the treatment of pneumonia with bacteriophages does not lead to an increase in the existing inflammatory response, and in some cases can reduce it, promoting a more rapid restoration of blood counts.

* Dufour N, Delattre R, Chevallereau A et al. Phage therapy of pneumonia is not associated with an over stimulation of the inflammatory response compared to antibiotic treatment in mice // Antimicrobial Agents and Chemotherapy, June 2019, AAC.00379-19. DOI: 10.1128/AAC.00379-19