UTI antibiotic of choice appears to have a high resistance rate

July 1, 2010

The antibiotic of choice for simple urinary tract infections, trimethoprim-sulfamethoxazole, has a resistance rate of 23% to the bacteria commonly associated with UTIs.

San Francisco-The antibiotic of choice for simple urinary tract infections, trimethoprim-sulfamethoxazole (TMP-SMX [Bactrim, Septra], has a resistance rate of 23% to the bacteria commonly associated with UTIs, researchers at the Vattikuti Urology Institute at the Henry Ford Health Care System, Detroit, have found.

Two other antibiotics-ciprofloxacin (Cipro, Proquin XR) and nitrofurantoin (Furadantin, Macrobid, Macrodantin)-have much lower rates of resistance to the bacteria (8% and 2%, respectively). Ampicillin (Prinicpen) is typically not recommended any more because of the high resistance rate (44%).

For the study, which was presented at the AUA annual meeting, the researchers looked at the resistance rates for four drugs (ampicillin, ciprofloxacin, TMP-SMX, and nitrofurantoin). Using a Medline search, they reviewed articles published from 1999 to 2009 that reported resistance patterns from Escherichia coli-related community-acquired UTIs. During this period, the rate of resistance to one drug-TMP-SMX, the recommended empiric treatment for simple UTIs-increased to about 30%, said first author Frank J. Penna, MD, a urology resident at the Vattikuti Urology Institute. Most of the patients were symptomatic, and all had diagnoses that were confirmed with a culture.

"It is likely that the bacteria are evolving a lot quicker than we are," Dr. Penna told Urology Times. "Several decades ago, UTIs were easy to treat, and usually there was no need to worry about what antibiotic to use."

However, within the past few decades, bacteria have become more resistant to antibiotics, adding to the expense of treatment.

In addition, under-treatment can lead to complications such as recurrence, and undertreated infections can lead to more serious problems, such as kidney infections and sepsis, that require hospital admission, said Dr. Penna, who worked on the study with Mireya Diaz, PhD, and Jack S. Elder, MD.

Careful antibiotic selection needed

The study has implications for clinical practice-in particular, that of primary care providers, who usually treat uncomplicated UTIs.

"The intention is to increase the awareness of the resistance rates," Dr. Penna said. "By doing that, two changes might take place: prescribing a different antibiotic, preferably nitrofurantoin. Also, physicians may need to vary the antibiotic that they use."

Overuse is the most likely culprit for the resistance, he said, adding that primary care doctors need to be more cautious when choosing the antibiotic they prescribe.

"It seems like a simple problem-the patient comes into the office with symptoms of a UTI, and you prescribe them an antibiotic," Dr. Penna said. "But now it's become a possibly expensive endeavor."

A urine culture should be taken to identify the type of bacteria, and determine whether the bacterium is resistant to certain antibiotics.

"The culture can take up to 3 days," Dr. Penna said, "and most physicians would like to send the patient home with an antibiotic that is likely to treat the symptoms and eradicate the infection."