UCLA Study Finds Unprecedented Bacterial Resistance To Standard Antibiotic In Treating Kidney Infections

A UCLA study published in this week's Journal of the American Medical Association showed that the bacteria causing kidney infections, one of the most common serious infections affecting adult women, has become resistant to a standard antibiotic, leading to treatment failure and increased health care costs. The highest bacterial resistance was found on the West Coast.

The study found that trimethoprim/sulfamethoxazole or TMP/SMX (also known as Bactrim® and Septra®), a standard antibiotic for kidney infections, led to more treatment failures and increased costs than ciprofloxacin (Cipro®), a common fluoroquinolone antibiotic. Ciprofloxacin demonstrated greater efficacy, with high cure rates when given for only seven days, one-half the usual treatment duration for kidney infection.

"Most treatment failures in the study were directly related to bacterial resistance, most often to E. coli," said Dr. David Talan, principal investigator, UCLA professor of medicine, and department chairman, emergency medicine, Olive-View UCLA Medical Center. "The study highlights the growing impact of bacterial resistance and the need to reevaluate antibiotics and treatment."

The multi-site national study involved 255 women, average age 25, with acute uncomplicated pyelonephritis, a serious type of kidney infection. Patients joined one of two study groups by random selection. One group received ciprofloxacin (500 mg) twice a day for seven days, followed by a placebo for seven days. Patients in the second group received TMP/SMX (160/800 mg) twice a day for 14 days.

At four to 11 days following treatment, the number of patients cured -- or having symptoms of illness disappear -- reached 96 percent for patients who took ciprofloxacin compared with 83 percent of the women who received TMP/SMX. The bacterial eradication rates for the ciprofloxacin group was 99 percent, compared with 89 percent for TMP/SMX group. "Physicians may wish to re-evaluate their choice of antibiotic for patients with kidney infections," said Talan, who is also an infectious disease expert. "We may have identified a better way to treat these kidney infections using ciprofloxacin. The shorter treatment time means patients may comply better, and are more successfully cured with lower costs."

The study also found that nearly 18 percent of isolated strains of E. coli, the bacteria responsible for approximately 90 percent of all cases of pyelonephritis, were resistant to TMP/SMX. None were found to be resistant to ciprofloxacin.

"Bacterial resistance directly related to lower cure rates," said Talan. "This is an important example of how laboratory-detected antibiotic resistance can predict the likelihood that a patient will recover from a serious infection." In addition, the E. coli bacterial resistance to the standard antibiotic was most prevalent on the West Coast -- 32 percent of the strains were resistant, compared to the Midwest at 14 percent and East Coast at 7 percent.

"If physicians find a 10 percent to 15 percent resistance rate in their patient population to TMP/SMX, they may want to reassess the antibiotic they are using," said Talan. "The next step is to explore why the bacterial resistance is so high in certain locations." Talan is presently working with the Centers for Disease Control and Prevention to further study this problem.

Treatment costs were 30 percent higher for patients receiving TMP/SMX, averaging $687 per patient compared to $531 per patient for those receiving ciprofloxacin. Total treatment costs included drugs, hospitalizations, office visits, laboratory and other tests.

"The higher clinical failure rate with the standard antibiotic led to additional courses of antibiotics, and increased days of subsequent hospitalization, office visits, and laboratory tests, resulting in higher overall costs," said Talan.

Drug-related side effects were reported at 24 percent for patients using ciprofloxacin and 33 percent for patients on TMP/SMX. Adverse effects mostly included gastrointestinal complaints, headache, dizziness and rash in both groups.

At the discretion of their treating physician, about one-third of ciprofloxacin study patients and one-third of the TMP/SMX patients also received an initial intravenous dose of either 400 mg of ciprofloxacin or 1000 mg of ceftriaxone respectively. These patients were not chosen at random, so no conclusions could be drawn about the effects of this type of antibiotic therapy in the context of the study.

Kidney infections, or pyelonephritis, affect 250,000 women each year and lead to 100,000 hospitalizations annually. Symptoms include high fever, chills, severe back pain, nausea, vomiting, and painful, frequent urination. Left untreated, these infections can lead to life-threatening complications.

The study was funded by Bayer, a research-based pharmaceutical company with major businesses in health care and life sciences. Bayer manufactures ciprofloxacin (Cipro®). The safety and effectiveness of ciprofloxacin in children, adolescents less than 18 years of age, pregnant women and lactating women have not been established.