Clinical

IV vancomycin linked to rectal colonization with vancomycin-resistant enterococci

Last Updated: 2004-12-02 16:25:49 -0400 (Reuters Health)

NEW YORK (Reuters Health) - New evidence suggests that intravenously administered vancomycin is excreted by way of the biliary tract into stool. According to investigators at Albert Einstein College of Medicine in Bronx, New York, this may represent the means by which vancomycin-resistant enterococci (VRE) attain their status as one of the most common etiologies of hospital-acquired infection in the US.

A major reservoir of the pathogen consists of patients with VRE rectal colonization, Drs. Brian P. Currie and Luciano Lemos-Filho explain in their paper, published in the November issue of Antimicrobial Agents and Chemotherapy. But up until now, the presence of vancomycin in stool was believed to be uncommon and not clinically significant, with the antibiotic excreted almost exclusively in urine.

However, the authors had previously shown an increased prevalence of VRE rectal colonization in patients receiving IV vancomycin for 5 days or longer.

For their current study, stool samples were prospectively collected from 31 patients undergoing IV vancomycin therapy, and bile samples from 2 who had also undergone external biliary stenting. Samples were assayed for vancomycin concentrations.

Forty-six stool samples were obtained from 23 patients who were treated with 1 g vancomycin b.i.d. Vancomycin was present in 5 of 26 samples (19.2%) collected < 5 days into therapy (up to 3.9 microgram/mL of stool supernatant). Among those receiving 5 days or more therapy, 26 of 28 (92.9%) had detectable levels (3.3 to 94.8 micrograms/mL).

The authors also assayed samples from nine patients treated with IV vancomycin 1 g q.d. Only one sample, collected on day 7 of therapy, was positive for detectable vancomycin (8.8 microgram/mL).

All five bile samples, collected on days 7 to 23 of treatment, were positive for vancomycin, at levels of 8.2 to 12.5 microgram/mL.

The authors suggest that the observed levels of vancomycin in stool could disrupt the natural bowel anaerobic flora, a process associated with VRE colonization.

"There has been a lot controversy over what role vancomycin plays in human VRE rectal colonization," Dr. Currie told Reuters Health. "The one thing that did not make sense to many people was, for a drug that does not penetrate the bowel, how could it be exerting a selective pressure?"

"The answer is it does enter the bowel in almost everybody through biliary excretion, certainly at concentrations that could select or enrich for VRE."

Dr. Currie noted that vancomycin is frequently used as empiric therapy. He recommends that once culture and sensitivity results are in, vancomycin should be discontinued if there are other treatment alternatives.

Antimicrob Agents Chemother 2004;48:4427-4429.