From the Guidelines
Keflex (cephalexin) is not the most recommended treatment for E. coli infections due to varying resistance rates, and its use should be guided by local antimicrobial susceptibility patterns and individual patient factors. When considering treatment for E. coli infections, particularly those affecting the urinary tract, it's crucial to take into account the antimicrobial resistance patterns of the specific region and the individual patient's history with antibiotics [ 1 ]. The resistance rates of E. coli to various antimicrobials, including first- and second-generation oral cephalosporins like cephalexin, can vary significantly by geographic location [ 1 ]. While cephalexin may be effective against some E. coli strains, its efficacy can be compromised in areas with high resistance rates, making it essential to consider alternative antimicrobials such as nitrofurantoin, fosfomycin, or mecillinam, which have shown good in vitro activity against E. coli in various regions [ 1 ]. Key factors to consider in the choice of antimicrobial include the patient's recent travel history, previous use of antimicrobials, and local resistance patterns [ 1 ]. Given the potential for resistance and the importance of effective treatment, susceptibility testing is recommended for complicated or recurrent E. coli infections to guide the selection of the most appropriate antimicrobial therapy. In cases where cephalexin is deemed appropriate based on susceptibility testing, the typical adult dosage for uncomplicated urinary tract infections is 250-500 mg taken orally every 6 hours, or 500 mg every 12 hours, for 7-14 days depending on infection severity [ 1 ]. However, the decision to use cephalexin should always prioritize the most recent and highest quality evidence available, considering morbidity, mortality, and quality of life outcomes.
From the Research
Keflex and E. coli Infections
- Keflex, also known as cephalexin, is a semisynthetic cephalosporin antibiotic used to treat various bacterial infections 2.
- The antimicrobial spectrum of cephalexin includes pathogens commonly encountered in clinical practice, such as those causing upper and lower respiratory tract, skin and soft tissue, and genitourinary tract infections 2.
- Cephalexin is effective against many urinary tract pathogens, with concentrations in urine many times greater than the minimum inhibitory concentration for these pathogens 2, 3.
Efficacy Against E. coli
- E. coli is a common cause of urinary tract infections, and cephalexin has been shown to be effective in treating these infections 2, 3.
- Studies have demonstrated that cephalexin can achieve high concentrations in urine, making it effective against E. coli and other urinary tract pathogens 2.
- However, the effectiveness of cephalexin against E. coli can depend on various factors, such as the severity of the infection and the presence of any underlying medical conditions 2, 3.
Important Considerations
- Cephalexin is not effective against all types of bacteria, and its use should be guided by culture and sensitivity testing to ensure that the causative organism is susceptible to the antibiotic 2, 3.
- Patients with creatinine clearances less than 30 ml/min may require a reduction in cephalexin dosage, which should be proportional to the reduced function 2.
- Cephalexin can cause adverse effects, such as gastrointestinal upset, rash, and urticaria, although these are relatively infrequent and usually do not require discontinuance of the drug 4, 5.