Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Drug-Resistant UTIs Are Harder to Treat

Dear Doctor: I had a urinary tract infection that improved on the antibiotic Keflex, but lab tests showed the bacteria was actually resistant to the Keflex, so I had to switch to a different antibiotic. I don’t understand -- if the infection was resistant, why did the symptoms go away?

Dear Reader: Urinary tract infections, or UTIs, are one of the most common bacterial infections in the U.S. They occur when bacteria -- in the majority of cases it’s E. coli -- colonize any of the tissues or structures of the urinary system. This includes the kidneys, which filter waste and excess water from the blood to make urine; the ureters, which are the tubes through which urine leaves the kidneys; the bladder, where urine is stored; and the urethra, through which urine leaves the body.

Although both men and women can get a UTI, the condition is more common in women. According to some estimates, anywhere from 40% to 60% of women will have at least one UTI in their lifetime. Symptoms can include urine that is dark, cloudy, bloody or pungent, an urgent need to urinate that yields very little urine, pain or burning during urination, and abdominal pain. In the elderly, a UTI can present without any physical symptoms, but result in confusion or temporary cognitive impairment.

Unfortunately, as you have experienced firsthand, urinary tract infections are becoming increasingly challenging to treat. This is due to the growing problem of drug-resistant pathogens, which affect an estimated 2 million people in the United States every year. Antibiotic resistance happens when drugs are no longer effective at completely eradicating the bacteria and fungi that cause infection and disease. That means that although some of the bacteria or fungi may be killed by the drug, others aren’t. Those that are resistant to the drug will continue to grow and reproduce, causing the disease or condition to persist.

We suspect that in your case, the initial antibiotic killed enough of the bacteria that were causing your UTI for the symptoms to abate and afford you physical relief. However, because the infection included bacteria that were resistant to Keflex, the UTI was not being cured. Those bacteria that were resistant to Keflex were continuing to grow. Fortunately, your health care provider followed the current guidelines to send a urine sample out to test for antibiotic resistance. Using the results of those lab tests, you were prescribed a different and ideally more effective antibiotic. In some cases, it can take multiple attempts with different antibiotics to successfully vanquish a UTI. Whichever drug is prescribed, be sure to ask about potential interactions with food or other drugs, and to complete the regimen, even after symptoms go away.

Because of the risk of the infection moving to the kidneys, it’s important to make sure that a UTI is completely cleared up. Patients whose urinary tract infection is caused by a drug-resistant strain of bacteria should continue to be followed after antibiotic therapy is complete. We recommend at least one repeat urine test to “test for cure” and make sure that the UTI has been completely eradicated.

(Send your questions to, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)