Problem of antimicrobial resistance of fecal aerobic gram-negative bacilli in the elderly

In this study, we assessed the magnitude of risk (odds ratio [OR]) of patients being colonized with fecal aerobic gram-negative bacilli in two geriatric hospitals compared with the community, and we associated the use of antimicrobial agents with bacterial resistance. One fecal sample was collected from each of 341 patients, aged 60 years or older, during the hospital stay or when visiting the outpatient service. Samples were collected in 1988 and 1993 to 1994. The aerobic gram-negative bacilli from all samples were examined for resistance to seven antimicrobials by a replica plating method. The long-term-hospitalized patients had a significantly higher risk of being colonized with bacilli resistant to ampicillin (OR, 14.3; 95% confidence interval [95% CI], 6.0 to 34.1), cefuroxime (OR, 7.5; 95% CI, 2.7 to 20.8), trimethoprim (ORs, 22.3; 95% CI, 8.6 to 57.8), and tetracycline (OR, 5.2; 95% CI, 2.4 to 10.9) than the outpatients. The respective ORs among the short-term-hospitalized patients compared with the outpatients were 4.0 (95% CI, 1.9 to 8.4), 7.5 (95% CI, 2.7 to 20.8), 5.5 (95% CI, 2 to 14), and 2.0 (95% CI, 1 to 4). In 1993 to 1994 compared with 1988, in both hospitals there was a significantly increased risk of colonization by bacilli resistant to ampicillin (OR, 3.1; 95% CI, 1.9 to 5.1), cefuroxime (OR, 3.8; 95% CI, 2.1 to 6.7), and tetracycline (OR, 1.6; 95% CI, 1.0 to 2.5). However, the total use of antimicrobial agents increased only among the patients of the short-term-care hospital.