Indications for Fosfomycin Fosfomycin has a broad spectrum of activity against both gram-positive and gram-negative organisms, including many antibiotic-resistant organisms such as Staphylococcus aureus, including methicillin-resistant S aureus (MRSA) Enterococcus species, including vancomycin - resistant enterococci (VRE) Enterobacterales (formerly Enterobacteriaceae), including extended-spectrum beta-lactamase (ESBL) - producing and carbapenem-resistant Klebsiella pneumoniae Escherichia coli, including fluoroquinolone-resistant E coli Pseudomonas aeruginosa, which has variable rates of resistance Oral fosfomycin should be used only for uncomplicated (ie, lower) urinary tract infections caused by susceptible pathogens.