A Phase 4 interventional study of Fosfomycin Trometamol Salt and control group in Prostatitis and Escherichia Coli Infection, sponsored by Hospital Mutua de Terrassa. Completed at 7 sites in Spain. Open to male participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-28.
Sponsored by Hospital Mutua de Terrassa · Phase 4, Interventional, and Treatment
FOS-PROST was a prospective, non-randomized, controlled phase IV clinical trial designed to evaluate the clinical and microbiological efficacy of oral fosfomycin trometamol as sequential antibiotic therapy in patients with acute bacterial prostatitis caused by multidrug-resistant *Escherichia coli*.
According to the study protocol, patients with multidrug-resistant *E. coli* were assigned to receive oral fosfomycin trometamol, whereas patients with non-multidrug-resistant *E. coli* were assigned to receive conventional oral antibiotic treatment with ciprofloxacin or trimethoprim-sulfamethoxazole, according to antimicrobial susceptibility testing.
All patients received 1 to 5 days of appropriate intravenous antibiotic therapy before switching to oral treatment. Fosfomycin trometamol was administered at a standard dose of 3 g once daily. The planned total duration of antibiotic treatment was 21 days in both groups, including intravenous and oral therapy.
During study conduct, some patients with non-multidrug-resistant *E. coli* also received fosfomycin. All patients with multidrug-resistant *E. coli* received fosfomycin.
Clinical and microbiological outcomes were compared between treatment groups. Secondary objectives included evaluating carbapenem consumption, hospital length of stay, safety, recurrence, and fosfomycin pharmacokinetics.
Acute bacterial prostatitis caused by multidrug-resistant *Escherichia coli* represents a therapeutic challenge because resistance to commonly used oral antibiotics limits treatment options and may increase the need for prolonged intravenous antibiotic therapy.
FOS-PROST was a multicenter, prospective, non-randomized, controlled phase IV clinical trial investigating oral fosfomycin trometamol as sequential antibiotic treatment for acute bacterial prostatitis caused by multidrug-resistant *E. coli*.
Eligible adult male patients with microbiologically confirmed acute bacterial prostatitis caused by *E. coli* were enrolled. All participants received 1 to 5 days of appropriate intravenous antibiotic therapy before switching to oral treatment, once clinical stability and the conditions for oral sequential therapy had been achieved.
According to the study protocol, patients with multidrug-resistant *E. coli* were assigned to receive oral fosfomycin trometamol at a standard dose of 3 g every 24 hours. Patients with non-multidrug-resistant *E. coli* were assigned to receive conventional oral antibiotic therapy with ciprofloxacin or trimethoprim-sulfamethoxazole, according to antimicrobial susceptibility testing.
The planned total duration of antibiotic treatment was 21 days in both groups, including intravenous and oral therapy.
During study conduct, some patients with non-multidrug-resistant *E. coli* received oral fosfomycin rather than conventional oral antibiotic therapy. All patients with multidrug-resistant *E. coli* received fosfomycin.
The study evaluated clinical cure and microbiological cure as separate efficacy outcomes. Secondary outcomes included recurrence, adverse events, carbapenem consumption, hospital length of stay, and fosfomycin pharmacokinetics.
The statistical analysis included a comparison according to the treatment actually received (as-treated analysis) and a per-protocol analysis excluding patients who did not meet the protocol-defined treatment allocation criteria.
88 studies on the registry are indexed under Prostatitis; 11 are open to participants now.
This study's enrollment of 88 is above the median of 60 across 73 interventional studies indexed under Prostatitis.
Browse Prostatitis studies →Hospital Mutua de Terrassa is the lead sponsor of 35 studies on the registry; 12 are open to participants now.
Counted across the registry records on this site, refreshed daily.
**Inclusion Criteria:**
Male patients aged 18 years or older with febrile acute bacterial prostatitis (temperature >37.5°C) caused by Escherichia coli.
Diagnosis required a prostate-specific antigen (PSA) level >4 μg/L, at least one microbiological criterion, and at least two clinical criteria as specified below.
**Microbiological Criteria (at least one required):**
**Clinical criteria (at least two required):**
Lower urinary tract symptoms:
Perineal pain, spontaneous or associated with urination:
History of prostatic disease (prostate cancer or benign prostatic hyperplasia) associated with:
**Exclusion Criteria:**
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Biopsy and archival tissue
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Adult male patients with acute bacterial prostatitis caused by multidrug-resistant Escherichia coli, according to the Magiorakos criteria, assigned to receive sequential oral fosfomycin trometamol at a standard dose of 3 g every 24 hours after 1 to 5 days of appropriate intravenous antibiotic therapy.
Drug: Fosfomycin Trometamol Salt
Adult male patients with acute bacterial prostatitis caused by non-multidrug-resistant Escherichia coli, assigned to receive sequential oral antibiotic treatment with ciprofloxacin or trimethoprim-sulfamethoxazole, according to antimicrobial susceptibility testing, after 1 to 5 days of appropriate intravenous antibiotic therapy.
Drug: control group
Oral fosfomycin trometamol, 3 g every 24 hours, administered as sequential antibiotic therapy after 1 to 5 days of appropriate intravenous antibiotic treatment, once clinical stability and oral tolerance were achieved. The planned total duration of antibiotic treatment, including intravenous and oral therapy, was 21 days. Dose adjustments for renal impairment were specified in the protocol.
Also known as: J01XX01 - FOSFOMICINA
Oral ciprofloxacin, 500 mg every 12 hours, administered as sequential antibiotic therapy according to antimicrobial susceptibility testing, following 1 to 5 days of appropriate intravenous antibiotic treatment. The planned total duration of antibiotic therapy was 21 days.
Oral trimethoprim-sulfamethoxazole, 160 mg/800 mg every 12 hours, administered as sequential antibiotic therapy according to antimicrobial susceptibility testing, following 1 to 5 days of appropriate intravenous antibiotic treatment. The planned total duration of antibiotic therapy was 21 days.
Percentage of Participants With Clinical Cure
Clinical cure was defined as the resolution of all symptoms present at baseline without the need for additional antibiotic treatment. Clinical cure required the absence of fever (axillary temperature greater than 38°C), urinary symptoms (dysuria, urinary frequency, urgency, or suprapubic pain), and altered level of consciousness if present at baseline.
Time frame: Day 21 ± 3 days from treatment initiation (end of treatment)
Percentage of Participants With Microbiological Cure
Microbiological cure was defined as a negative urine culture at the end of antibiotic treatment. Only participants with an available urine culture at the end-of-treatment assessment were included in the analysis of this outcome. Participants without an available urine culture were excluded from the microbiological cure analysis.
Time frame: Day 21 ± 3 days from treatment initiation (end of treatment).
Estimated Carbapenem Defined Daily Doses (DDDs) Avoided per Patient
The potential carbapenem-sparing effect of sequential oral fosfomycin trometamol was estimated in patients with acute bacterial prostatitis caused by multidrug-resistant Escherichia coli. Assuming that these patients would otherwise have received intravenous ertapenem until completion of the planned 21-day antibiotic course, the number of potentially avoided ertapenem Defined Daily Doses (DDDs) was calculated based on the remaining treatment duration after switching to oral fosfomycin. Results were expressed as estimated DDDs avoided per patient.
Time frame: During the 21-day antibiotic treatment period.
Hospital Length of Stay in Days
Hospital length of stay was assessed as the number of days of actual hospital admission during the acute bacterial prostatitis episode and compared between the fosfomycin and control group. In accordance with the study protocol, patients with hospital-acquired multidrug-resistant Escherichia coli infection were excluded from this analysis
Time frame: During the hospital admission for the acute bacterial prostatitis episode.
Estimated Hospitalization Days Avoided per Patient
The potential reduction in hospital or hospital-at-home admission days associated with sequential oral fosfomycin trometamol was estimated among patients receiving oral fosfomycin. Assuming that these patients would otherwise have required continued parenteral antibiotic therapy during hospital or hospital-at-home admission, the number of potentially avoided admission days was estimated from the remaining days of the planned 21-day antibiotic treatment course after switching to oral fosfomycin. Results were expressed as estimated admission days avoided per patient.
Time frame: During the 21-day antibiotic treatment period
Plasma Fosfomycin Concentration
Plasma fosfomycin concentrations (mg/L) were planned to be measured using blood samples collected at predefined time points after oral fosfomycin trometamol administration in selected participants at the coordinating center. The planned pharmacokinetic assessment was not performed, and no plasma fosfomycin concentration data were collected.
Time frame: At 1, 2, 4, 12, and 24 hours after the first oral fosfomycin dose; additional trough concentrations during hospitalization or at Visit 4, as applicable.
Percentage of Participants Experiencing Adverse Events
The incidence and severity of adverse events were assessed in patients receiving sequential oral fosfomycin trometamol or conventional oral antibiotic therapy. Adverse events were recorded during antibiotic treatment and subsequent follow-up through Day 51 (± 7 days) from treatment initiation. Results were expressed as the number and percentage of participants experiencing adverse events in each treatment group, with assessment of their severity.
Time frame: From treatment initiation through Day 51 (± 7 days).
Acute Bacterial Prostatitis-Related Mortality
Mortality related to the acute bacterial prostatitis episode was assessed in both treatment groups. The outcome was measured as the number and percentage of participants who died from causes attributable to the acute bacterial prostatitis episode during the study observation period.
Time frame: From treatment initiation through Day 51 (± 7 days).
Incidence of Acute Bacterial Prostatitis Recurrence
The incidence of acute bacterial prostatitis relapse or reinfection was assessed prospectively during the protocol-defined follow-up period. Relapse was defined as recurrence of urinary tract infection symptoms with isolation of the same microorganism, whereas reinfection was defined as recurrence of symptoms with isolation of a different bacterial strain. Results were expressed as the number and percentage of participants experiencing relapse or reinfection in each treatment group.
Time frame: From completion of antibiotic treatment through Day 51 (± 7 days) from treatment initiation.
Incidence of Emergent Fosfomycin Resistance
The emergence of fosfomycin resistance was planned to be assessed through microbiological susceptibility testing during treatment and follow-up in participants receiving oral fosfomycin trometamol. This assessment was not performed, and no data on emergent fosfomycin resistance were collected.
Time frame: From treatment initiation through Day 51 (± 7 days).
Plan to share: No
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Studies of the drug tested here: Fosfomycin
Hospital Mutua de Terrassa