Examples of various antimicrobial resistance patterns in Escherichia coli.

E. coli and UTIs

The most common cause of urinary tract infections (UTIs) is bacterial infection, specifically from Escherichia coli (E. coli), which is responsible for about 80-90% of all UTIs.

When E. coli bacteria enter the urinary tract, they can cause infections, particularly in the bladder (cystitis) and urethra (urethritis), and sometimes, they can spread to the kidneys (pyelonephritis), causing more severe infections.

What is Empiric Therapy?

Empiric therapy refers to the use of medications—most commonly antibiotics—based on a healthcare provider's clinical judgment to treat a suspected infection before the causative organism is identified through laboratory tests.

It is guided by:

• The patient’s symptoms and medical history.
• Knowledge of common pathogens likely causing the infection.
• Local patterns of antibiotic resistance.

For example, in a urinary tract infection (UTI), a provider may prescribe an antibiotic known to work against E. coli, the most common bacteria causing UTIs, without waiting for lab results.
Common first-line antibiotics: nitrofurantoin, trimethoprim-sulfamethoxazole, or fosfomycin.

Urine Testing

A urine sample may be sent for testing under the following circumstances:

• Severe symptoms or when symptoms don’t improve after starting treatment.
• Concern about antibiotic resistance.
• Recurrent UTIs or frequent infections.
• Complicated UTIs, such as those in men, pregnant individuals, or people with other risk factors.

Tailoring the Treatment

If a urine culture is performed, the results usually take 24–48 hours.
The initial antibiotic may be adjusted if the bacteria are resistant to it or if the culture identifies a different causative organism (e.g., UTI caused by Proteus spp. treated with nitrofurantoin).