Does Cephalexin (Keflex) treat Escherichia coli (E. coli) infections?

From the Guidelines

Yes, Keflex (cephalexin) can treat E. coli infections, particularly those affecting the urinary tract. The most recent and highest quality study, 1, provides recommendations on first- and second-choice antibiotics for empiric treatment of clinical infections, including urinary tract infections.

Key Points:

• The typical adult dosage for uncomplicated urinary tract infections is 500 mg every 12 hours or 250 mg every 6 hours for 7-14 days, depending on infection severity.
• For children, the dosage is typically 25-50 mg/kg/day divided into 2-4 doses, as stated in 1.
• Keflex works by inhibiting bacterial cell wall synthesis, causing the bacteria to rupture and die.
• However, some E. coli strains have developed resistance to Keflex, so susceptibility testing is often recommended before treatment, as noted in 1.
• Patients should complete the full course of antibiotics even if symptoms improve, drink plenty of water during treatment, and contact their healthcare provider if symptoms worsen or don't improve after a few days.
• Side effects may include diarrhea, nausea, and allergic reactions, particularly in those with penicillin allergies.

Considerations:

• Local patterns of susceptibility of coliforms to antimicrobial agents, particularly trimethoprim-sulfamethoxazole and cephalexin, should be taken into account during selection of an antimicrobial agent before sensitivity results are available, as stated in 1.
• The Expert Committee recommends amoxicillineclavulanic acid, nitrofurantoin, and sulfamethoxazoleetrimethoprim as the first-choice options for the treatment of lower urinary tract infections, as noted in 1.
• Ciprofloxacin was recommended as the first-choice option for empiric treatment of mild-to-moderate pyelonephritis and prostatitis if local/national data on antimicrobial resistance patterns allow its use, as stated in 1.

From the FDA Drug Label

Cephalexin is indicated for the treatment of the following infections when caused by susceptible strains of the designated microorganisms: ... Genitourinary tract infections, including acute prostatitis, caused by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae Cephalexin treats Escherichia coli (E. coli) infections, specifically genitourinary tract infections caused by susceptible strains of E. coli 2.

• Key points:
  • Cephalexin is effective against E. coli in genitourinary tract infections
  • Culture and susceptibility tests should be performed prior to and during therapy to ensure the bacteria is susceptible to cephalexin.

From the Research

Cephalexin (Keflex) Treatment for Escherichia coli (E. coli) Infections

• Cephalexin is an oral cephalosporin that has been used to treat urinary tract infections (UTIs) caused by E. coli 3.
• Studies have shown that cephalexin is effective in treating UTIs, with high concentrations achieved in the urine and adequate serum levels 3, 4.
• A review of clinical trials and experimental studies found that cephalexin has good early bacteriological and clinical cures in uLUTIs due to non-extended-spectrum beta-lactamase-producing (ESBL) Enterobacteriaceae, comparable to many traditionally first-line agents 4.
• A retrospective review of patients discharged from the emergency department who received cephalexin for the treatment of uncomplicated UTIs found that 81.1% of patients met the criteria for clinical success 5.

Resistance and Treatment Options

• The increasing resistance of E. coli to first-line antibiotic therapies has necessitated the need for alternative agents, including cephalexin 5, 4.
• Cephalexin may be a suitable option for the empiric treatment of uncomplicated UTIs, particularly in areas with high rates of resistance to other antibiotics 5, 4.
• Other treatment options for UTIs caused by E. coli include fluoroquinolones, injectable third-generation cephalosporins, and aminoglycosides, although these may have limitations due to resistance or adverse effects 6.
• The choice of antibiotic therapy should be guided by local susceptibility patterns and adjusted based on the results of antimicrobial susceptibility testing 7, 6.