Researchers from the Foundation take part in a pioneering study evaluating a new therapeutic option for legionellosis

23/12/2025

Researchers from the Foundation for the Fight against Infections and the Germans Trias i Pujol Research Institute (IGTP), including Dr Lluïsa Pedro-Botet, head of the Severe Bacterial Infections line and co-head of the Infections in Immunocompromised People line at the Foundation, have published a groundbreaking study in the International Journal of Infectious Diseases on the activity of delafloxacin. This is a new antibiotic targeting bacteria of the Legionella genus inside cells. The study was sponsored by Menarini Italy.

This research also involved Drs Nieves Sopena, Esteban Reynaga and Javier Díez de los Ríos, members of the Foundation for the Fight against Infections and the Germans Trias i Pujol Hospital. Furthermore, the experiments were carried out at IGTP by Roger Cortes, under the direction and supervision of Dr Noemí Parraga, with the participation of Elisenda Arqué.

Legionellosis: a growing public health challenge

Legionellosis remains a public health problem in Europe, with an increasing incidence in recent years. In fact, in Spain, almost 2,000 cases were recorded in 2022, representing a 43% rise compared to the previous year.

The usual treatment is based on antibiotics such as levofloxacin, but the search for new alternatives is crucial given the rise in cases, the growing number of side effects and the potential emergence of resistance.

Key findings: greater efficacy and improved safety

The study, entitled “In vitro characterization of delafloxacin activity against intracellular Legionella: Exploring new treatment options for Legionnaires’ disease”, compared for the first time the efficacy of delafloxacin with levofloxacin in a cellular model of Legionella infection.

The results show that delafloxacin reduces the intracellular multiplication capacity of the bacterium between 5 and 10 times more than levofloxacin, with a minimum effective concentration (MIEC90) of 0.005 mg/l for most species and strains analysed, compared to 0.025 mg/l for levofloxacin. Moreover, considering the results of several pivotal clinical studies, delafloxacin demonstrates a superior safety profile.

These findings suggest that delafloxacin could become a more effective and safer therapeutic alternative for the treatment of legionellosis, although confirmation through clinical studies in real patients will be necessary. The involvement of researchers from the Foundation for the Fight against Infections in this work reinforces the institution’s commitment to translational research and improving the treatment of severe bacterial infections..