BOSTON—Clinicians may want to rethink the antibiotics they prescribe for vancomycin-resistant Enterococcus (VRE) urinary tract infections (UTIs).

A new retrospective study presented at the 50th Interscience Conference on Antimicrobial Agents and Chemotherapy found that newer broad-spectrum antibiotics and older narrow-spectrum antibiotics achieved similar clinical outcomes in patients with VRE UTI.

“If we have the opportunity to use a narrow-spectrum agent, why use a broad-spectrum agent that could potentially harm our patients?” asked lead investigator Hannah Palmer, PharmD, a clinical coordinator of infectious diseases in the department of pharmacy at St. Luke’s Episcopal Hospital in Houston. “A potential concern is that a future infection could be resistant to that broad-spectrum agent.”

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She also pointed out that newer agents may have drawbacks. For example, linezolid’s penetration into the urine is low and daptomycin is administered intravenously, she noted.

Even though VRE is a common pathogen in patients with nosocomial UTIs, the most appropriate antibiotic treatment has been unclear. Dr. Palmer and her colleagues investigated treatment patterns and outcomes of hospitalized patients with UTIs due to VRE. They classified patients according to infection severity (mild or moderate) and whether they received newer agents (linezolid or daptomycin) or older agents (ampicillin/amoxicillin, tetracyclines, or nitrofurantoin). All patients acquired their VRE UTI in the hospital.

The researchers identified 100 patients with VRE urine cultures. All had been admitted and treated at St. Luke’s between January 2009 and July 2009. VRE susceptibility was 100% for linezolid, 99% for daptomycin, 53% for tetracycline, 32% for nitrofurantoin, and 19% for ampicillin. VRE UTI severity was classified as moderate in 68 patients and mild in 32.

Mild disease was defined as asymptomatic bacteriuria while moderate disease included patients with any symptom of a true UTI. Antibiotics were given to 44% of patients with mild infection and 69% of patients with moderate infection. The newer antibiotics were more commonly given to patients with mild VRE UTI (100%) versus moderate (62%). Among the patients who received antibiotics for asymptomatic bacteriuria, 100% received a newer agent.

Dr. Palmer’s group found no significant differences in baseline characteristics among patients who received older versus newer agents. 

The investigators found that the average time to symptom resolution (5 days) was similar in patients receiving newer versus older antibiotics. The time spent in the hospital also was similar (30 days), regardless of the prescribed antibiotic. No patients had their antibiotics changed during the treatment course.  The investigators also found that 82% of the patients receiving newer antibiotics had isolates that were susceptible to at least one older agent.

“Currently, no studies have specifically evaluated the use of older, narrow spectrum agents for VRE UTIs,” Dr. Palmer said. “The increasing prevalence of VRE as a cause of UTIs is concerning to clinicians; however, the optimal treatment of choice remains unknown.”