Fosfomycin Response for the Patient Based on Susceptibility Testing
Based on the provided susceptibility data, this patient would likely respond well to fosfomycin for a urinary tract infection caused by the tested organism. 1, 2
Susceptibility Analysis
- The susceptibility data shows the organism is sensitive to multiple antibiotics including aminoglycosides, cephalosporins, fluoroquinolones, and carbapenems, suggesting it is likely an Enterobacterales species 3
- While fosfomycin susceptibility is not explicitly listed in the provided data, Enterobacterales (particularly E. coli and Klebsiella) generally show good susceptibility to fosfomycin 4, 5
- The organism shows resistance to ampicillin but sensitivity to ampicillin-sulbactam (intermediate in one test), suggesting a beta-lactamase producer that may still be susceptible to fosfomycin 3
Clinical Efficacy for UTIs
- Fosfomycin is highly effective as a first-line treatment for uncomplicated urinary tract infections, with a single 3-gram oral dose providing therapeutic urinary concentrations for 24-48 hours 1, 2
- Following oral administration, fosfomycin achieves mean urinary concentrations of 706 μg/mL within 2-4 hours, well above the MIC breakpoint for susceptible organisms (≤64 μg/mL) 2, 6
- Therapeutic urinary concentrations of fosfomycin (>100 μg/mL) are maintained for approximately 26 hours after a single dose 2
Important Considerations
- Fosfomycin is FDA-approved only for uncomplicated lower UTIs (cystitis) and should not be used for pyelonephritis or complicated UTIs as monotherapy 5, 1
- For complicated UTIs or pyelonephritis, alternative agents from the susceptibility panel (such as fluoroquinolones or cephalosporins) would be more appropriate 3, 5
- The organism shows variable susceptibility to nitrofurantoin (resistant in one test, sensitive in another), making fosfomycin potentially more reliable 6
Treatment Recommendations
- For uncomplicated lower UTI: Fosfomycin 3g oral powder dissolved in water as a single dose 1, 2
- For complicated UTI or pyelonephritis: Consider alternatives from the susceptibility panel such as ceftriaxone, ciprofloxacin, or levofloxacin based on the provided sensitivity data 3, 5
- If using fosfomycin for a multidrug-resistant organism, be aware that clinical data specifically for non-E. coli Enterobacterales is more limited 4, 7
Monitoring and Follow-up
- If symptoms do not resolve within 2-3 days or recur within 2 weeks after fosfomycin treatment, perform follow-up urine culture and consider alternative antibiotics based on the susceptibility panel 1
- Common adverse effects to monitor include diarrhea, nausea, and vomiting 1, 2