From the Guidelines
Fosfomycin is not recommended as a first-line treatment for urinary infections with Pseudomonas due to its limited efficacy against this bacterium. According to the latest guidelines, novel β-lactam agents such as ceftolozane/tazobactam and ceftazidime/avibactam are currently the first-line options for targeted treatment of invasive infections caused by Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-PA) 1.
Key Considerations for Treatment
- The treatment of Pseudomonas urinary tract infections (UTIs) requires careful selection of antibiotics due to the bacterium's inherent and acquired resistance mechanisms.
- Fluoroquinolones, carbapenems, and antipseudomonal cephalosporins are among the classes of antibiotics that have been used to treat Pseudomonas UTIs, but the choice should be guided by susceptibility testing whenever possible.
- In cases of complicated UTIs or infections caused by multidrug-resistant Pseudomonas strains, combination therapy may be necessary, and options like colistin-based therapy or newer agents such as imipenem/cilastatin–relebactam and cefiderocol might be considered, as suggested by recent guidelines 1.
Treatment Approach
- The primary approach should involve the use of antibiotics that are known to be effective against Pseudomonas aeruginosa, with a preference for those that have been recently endorsed by clinical guidelines, such as ceftolozane/tazobactam and ceftazidime/avibactam 1.
- Treatment duration should be tailored to the severity of the infection, typically ranging from 7 to 14 days.
- It is crucial to complete the full course of antibiotics as prescribed, even if symptoms improve quickly, to minimize the risk of recurrence and development of resistance.
- Patients should also be advised to drink plenty of fluids and to follow up with their healthcare provider to ensure the infection has been fully cleared.
From the Research
Treatment Options for Urinary Infection with Pseudomonas
- The treatment of urinary tract infections (UTIs) caused by Pseudomonas aeruginosa can be challenging due to antibiotic resistance 2.
- Fosfomycin is a broad-spectrum antibiotic that has been shown to be effective against Pseudomonas aeruginosa in some studies 3.
- However, other studies have reported that fosfomycin may not be effective against Pseudomonas aeruginosa, particularly in cases where the bacteria have developed resistance 4.
- Alternative treatment options for UTIs caused by Pseudomonas aeruginosa include fluoroquinolones, ceftazidime, cefepime, piperacillin-tazobactam, and carbapenems 2.
Efficacy of Fosfomycin against Pseudomonas
- A study published in 2020 found that fosfomycin was ineffective against Pseudomonas aeruginosa in a dynamic in vitro bladder infection model, despite high urinary concentrations and repeated daily doses for 7 days 4.
- Another study published in 2017 found that fosfomycin had in vitro activity against Pseudomonas aeruginosa, but the MIC50 and MIC90 values were higher than those for other antibiotics 3.
- A retrospective cohort study published in 2016 found that oral fosfomycin was effective in treating UTIs caused by Pseudomonas aeruginosa, but the study had limitations and the results should be interpreted with caution 5.
Resistance to Fosfomycin
- Resistance to fosfomycin has been reported in Pseudomonas aeruginosa, particularly in cases where the bacteria have been exposed to the antibiotic previously 4.
- A study published in 2017 found that the fosfomycin MIC50 and MIC90 values for Pseudomonas aeruginosa were 16 and 128 μg/mL, respectively, indicating a high level of resistance 3.
- Another study published in 2016 found that fosfomycin resistance was documented in 1% of Escherichia coli isolates and 19% of Klebsiella spp. isolates, highlighting the need for careful selection of patients and monitoring of resistance patterns 5.