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 antibiotics with minimal antianaerobic activity do not. 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 antianaerobic agents and agents with minimal antianaerobic activity. In a subgroup of 10 patients, cultures of environmental specimens (e.g., from bedding and clothing) were obtained. 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 of stool). 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 minimal antianaerobic 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 of less than 4 log per gram (P=0.002). 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.

Research from JAMA Internal Medicine — Unnecessary Use of Antimicrobials in Hospitalized Patients — Current Patterns of Misuse With an Emphasis on the Antianaerobic Spectrum of Activity

The intestinal tract provides an important reservoir for many nosocomial pathogens, including Enterococcus species, Enterobacteriaciae, Clostridium

Personal protective equipment (PPE) reduces, but does not eliminate, the risk of skin and clothing contamination with pathogens among health care personnel.^1-3 Even when gloves and gowns are worn, 2% to 5% of personnel caring for patients colonized with multidrug-resistant bacteria acquire the pathogens on their hands after glove removal.^4-6 In addition, 24% of personnel caring for patients with Clostridium difficile infection (CDI) had spore contamination on their hands after glove removal.⁷ High-risk exposures, such as handling contaminated body fluids, prolonged exposure, and failure to correctly use PPE, increased the risk of contamination.^4-7 Contamination of the skin and clothing of health care personnel contributes to transmission of pathogens and places personnel at risk for infection with potentially fatal pathogens, such as Ebola virus, severe acute respiratory syndrome, and Middle East respiratory syndrome coronaviruses.^1,8-11 Moreover, personnel frequently acquire norovirus infections during health care facility outbreaks and are at risk of acquiring CDI if they receive antibiotics.^12-14

For treatment of mild to moderate Clostridium difficile -associated disease (CDAD), oral metronidazole has been recommended as the preferred agent, in part due to concern that vancomycin may be more likely to promote colonization by vancomycin-resistant enterococci (VRE). We performed a prospective observational study to examine the effects of oral metronidazole or vancomycin treatment of CDAD on acquisition and concentration of VRE stool colonization. Before, during, and after 90 courses of CDAD therapy, stool samples were cultured for VRE, and the concentrations were quantified. Eighty-seven subjects (97%) had received antibiotics within the past month. For 56 treatment courses in which preexisting VRE colonization was present, metronidazole ( n = 37 courses) and vancomycin ( n = 19 courses), each promoted persistent VRE overgrowth during therapy, and the concentration decreased significantly in both groups by ∼2 weeks after completion of treatment ( P <0.049). For 34 treatment courses in which baseline cultures were negative for VRE, new detection of VRE stool colonization occurred during 3 (14%) of the 22 courses of metronidazole and 1 (8%) of the 12 courses of vancomycin ( P = 1.0). These results demonstrate that both oral metronidazole and oral vancomycin promote the overgrowth of VRE during treatment of CDAD. New CDAD treatments are needed that are less likely to disrupt the intestinal microflora and promote overgrowth of healthcare-associated pathogens.