Antibioticos

A N T IBIOT IC T HE RAP Y AND T HE DE NSIT Y OF VA NCOMYC IN-RES ISTA NT ENTER OCOCC I IN STOOL

EFFECT OF ANTIBIOTIC THERAPY ON THE DENSITY OF VANCOMYCINRESISTANT ENTEROCOCCI IN THE STOOL OF COLONIZED PATIENTS
CURTIS J. DONSKEY, M.D., TANVIR K. CHOWDHRY, M.D., MICHELLE T. HECKER, M.D., CLAUDIA K. HOYEN, M.D., JENNIFER A. HANRAHAN, D.O., ANDREA M. HUJER, B.S., REBECCA A. HUTTON-THOMAS, B.S.,CHRISTOPHER C. WHALEN, M.D., ROBERT A. BONOMO, M.D., AND LOUIS B. RICE, M.D.

ABSTRACT
Background Colonization and infection with vancomycin-resistant enterococci have been associated with exposure to antibiotics that are active against anaerobes. In mice that have intestinal colonization with vancomycin-resistant enterococci, these agents promote high-density colonization, whereas antibioticswith minimal antianaerobic activity do not. Methods We conducted a seven-month prospective study of 51 patients who were colonized with vancomycin-resistant enterococci, as evidenced by the presence of the bacteria in stool. We examined the density of vancomycin-resistant enterococci in stool during and after therapy with antibiotic regimens and compared the effect on this density of antianaerobicagents and agents with minimal antianaerobic activity. In a subgroup of 10 patients, cultures of environmental specimens (e.g., from bedding and clothing) were obtained. Results During treatment with 40 of 42 antianaerobic-antibiotic regimens (95 percent), high-density colonization with vancomycin-resistant enterococci was maintained (mean [±SD] number of organisms, 7.8± 1.5 log per gram ofstool). The density of colonization decreased after these regimens were discontinued. Among patients who had not received antianaerobic antibiotics for at least one week, 10 of 13 patients who began such regimens had an increase in the number of organisms of more than 1.0 log per gram (mean increase, 2.2 log per gram), whereas among 10 patients who began regimens of antibiotics with minimalantianaerobic activity, there was a mean decrease in the number of enterococci of 0.6 log per gram (P= 0.006 for the difference between groups). When the density of vancomycin-resistant enterococci in stool was at least 4 log per gram, 10 of 12 sets of cultures of environmental specimens had at least one positive sample, as compared with 1 of 9 sets from patients with a mean number of organisms in stool ofless than 4 log per gram (P=0.002). Conclusions For patients with vancomycin-resistant enterococci in stool, treatment with antianaerobic antibiotics promotes high-density colonization. Limiting the use of such agents in these patients may help decrease the spread of vancomycin-resistant enterococci. (N Engl J Med 2000;343:1925-32.)
©2000, Massachusetts Medical Society.

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N case–controlstudies, colonization and infection with vancomycin-resistant enterococci have been associated with exposure to vancomycin,1-6 third-generation cephalosporins,3-6 antibiotics that are active against anaerobes,3,6-8 ciprofloxacin,1 and aminoglycosides.4 The microbiologic basis for these associations is not well defined. If some antibiotics promote colonization and infection more than others that areequally effective, limiting the use of these agents may limit the spread of vancomycin-resistant enterococci. We previously examined the effect of various antibiotics on intestinal colonization with vancomycinresistant enterococci in mice.9 In mice with established colonization, as evidenced by the high density of vancomycin-resistant enterococci in stool, the administration of antibiotics withpotent activity against anaerobes maintained this level of colonization, whereas the administration of antibiotics with less potent antianaerobic activity did not.9 We prospectively tested the hypothesis that antianaerobic antibiotics promote high-density colonization with vancomycin-resistant enterococci, whereas antibiotics with minimal antianaerobic activity do not. In a subgroup of patients, we...