Fosfomycin is an antibiotic discovered since 1969. Disodium fosfomycin, for intravenous use (C3H5Na2O4P) is a bactericidal antibiotic, available in Italy since 2019 (AIFA approval). It works by blocking the enzyme UDP-N-acetylglucosamine enolpyruvil transferase, inhibiting the synthesis of peptidoglycan. It binds poorly to plasma proteins and is distributed very well in various tissues such as: eyes, bones, skin and subcutaneous tissue, muscles, lungs, prostate, bile and inflamed meninges. It also has a strong anti-biofilm activity.

Fosfomycin is active against Gram-positive bacteria (staphylococci, streptococci, enterococci, including MRSA and VRE) and Gram-negative bacteria (Enterobacterales, Haemophilus influenzae, Proteus mirabilis, Pseudomonas aeruginosa, including MDR strains) and against difficult-to-treat bacteria such as Serratia marcescens, Stenotrophomonas maltophilia, Bacteroides spp and intracellular bacteria such as Chlamydia and Mycoplasma. It has no activity against Acinetobacter spp, Peptococcus spp. and Peptostreptococcus spp, Burkholderia cepacia, and Mycobacterium tuberculosis.

IV fosfomycin is approved for the treatment of osteomyelitis, complicated urinary tract infections, pneumonia including hospital-acquired and ventilator-associated pneumonia, complicated skin and soft tissue infections, bacterial meningitis, and complicated bacteremia.

In this retrospective study, the investigators want to analyze the medical records of all patients admitted to the ASST of Lecco from 01/04/2020 to 31/12/2023 treated with fosfomycin IV in order to evaluate different clinical outcomes given the recent introduction at ASST Lecco

Inclusion Criteria:

• Age > 18 years;
• Patients hospitalized at A. Manzoni Lecco between April 2020 and December 2023;
• Patients treated with IV fosfomycin as monotherapy or in combination with other antibiotics for at least 72 hours.

Exclusion Criteria:

• Patients who received fosfomycin IV for less than 72h for any cause (death, adverse events, clinical decision).

Patients hospitalized at A. Manzoni Lecco between April 2020 and December 2023 and treated with IV fosfomycin as monotherapy or in combination with another antibiorics