For Empirical UTI Treatment, Know Your Pathogen Population

Kate Johnson

April 17, 2014

STOCKHOLM — Resistance rates to the 3 antibiotics most commonly used to treat urinary tract infections (UTIs) are higher than the cut off level suggested by guidelines, but penicillin remains largely effective, according to a new study.

Although the distribution of causative pathogens and their antibiotic resistance rates tend to differ significantly from region to region and country to country, the lessons learned from this study are of universal value, said Morkos Iskander, MD, from St Helens and Knowsley Teaching Hospitals in Prescot, United Kingdom. Prescribers might be wise to rethink their treatment choices.

"Different areas have different resistance profiles, so this probably needs to be run on a local basis, but most of these infections are in primary care. Everybody thinks we need brand new agents, but you can treat patients for less than a dollar with penicillin, an antibiotic that is 60 years old," Dr. Iskander told Medscape Medical News.

"We've changed prescribing practice in our largest district hospital and largest teaching hospital, and about 8 other hospitals are reviewing their data," he said.

Dr. Iskander presented the findings here at the European Association of Urology (EAU) 29th Annual Congress.

The researchers retrospectively analyzed all positive urine microbiology specimens from 11,094 patients (2237 male and 8857 female) over a 3-month period at a district general hospital.

The prevalence of causative bacteria and their resistance to common antibiotics were assessed, and patterns in the referring specialties of primary care, internal medicine, surgery, obstetrics and gynecology, pediatrics, and urology were compared.

Despite significant differences in referring specialties, Escherichia coli was by far the most common causative pathogen, occurring in 50% to 65% of all samples. Enterococcus was the next most common pathogen, in 9% to 20% of samples, and coliform bacteria were next, in 8% to 15%.

Although E coli was more prevalent in female than male patients (approximately 67% vs 45%), coliform was more common in men (17% vs 10%), as was Enterococcus (16% vs 9%).

Overall resistance rates were higher in pathogens from urology patients than from other patients (< .0004).

Table. Resistance Rates

Antibiotic Urology Patients, % Entire Cohort, %
Amoxicillin >55.0 49.0
Trimethoprim 40.3 31.3
Ciprofloxacin 30.0 22.7
Cephalexin 23.9 18.9
Amoxicillin/clavulanic acid 7.4 3.4
Gentamicin 8.5 5.5

 

It is possible that urology accrues patients "with resistant infection through active selection, as well as those who may have had exposure to multiple courses of antibiotics previously," explained Dr. Iskander.

EAU guidelines recommend culturing urinary samples from UTI patients to identify the causative pathogen and select appropriate treatment that has lower than 20% resistance, but clinical reality does not usually allow for this, he said.

"The problem is we want everyone to be treated rapidly, effectively, and quickly in the community, so treatment has to be empirical," said Dr. Iskander. "It takes 3 days to get a culture result and, for most women, I only need 3 days of amoxicillin/clavulanic to treat them."

This study shows that local populations of pathogens must be routinely checked for resistance, said session chair Robert Pickard, MD, professor of urology at Newcastle University in Newcastle upon Tyne, United Kingdom.

It seems that practitioners in the United Kingdom "are doing what they've been told in their guidance. They've been told that for a simple UTI, they should use short courses — 3 days — of trimethoprim, nitrofurantoin, or cephalexin," he told Medscape Medical News.

"Inevitably, that gives some degree of pressure to the bacteria to develop resistance to those antibiotics, particularly trimethoprim and cephalexin. I think this illustrates that it's a fluid system; you have to keep checking and alter your guidance accordingly," Dr. Pickard explained.

Dr. Iskander and Dr. Pickard have disclosed no relevant financial relationships.

European Association of Urology (EAU) 29th Annual Congress: Abstract 674. Presented April 13, 2014.

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