Impact of broad-spectrum antimicrobial treatment on the ecology of intestinal flora.

Suppression of intestinal flora by broad-spectrum antimicrobial agents facilitated risk of colonization or infection with resistant pathogen. We aimed to investigate the changes in bowel carriage of target resistant microorganisms (TRO) among patients treated with three different classes of Pseudomonas-sparing broad-spectrum antimicrobial agents (ertapenem, moxifloxacin and flomoxef) with anaerobic coverage. Risk factors for developing colonization of TRO were also analyzed. We prospectively enrolled the adult hospitalized patients (>20 years old) who were indicated for at least 7-day course with either of ertapenem, moxifloxacin or flomoxef. Rectal swabs were performed for the patients who received at least 1-day course of study antibiotics during the treatment duration. The TROs included Pseudomonas aeruginosa, Enterobacteriaceae, and Acinetobacter baumannii. MacConkey agars with study antibiotics were used to isolate the TROs and evaluate the antimicrobial resistance. The mean age of our study population was 61.6 years, and 58.8% were males. The rates of rectal colonization for Pseudomonas aeruginosa was similar among the study medications (ertapenem 13.2%, flomoxef 20%, moxifloxacin 14.3%, p = 0.809). Compared with ertapenem, flomoxef (odds ratio [OR], 4.30; 95% confidence interval [95% CI], 1.28-14.48, p = 0.019) and moxifloxacin (OR, 6.95; 95% CI, 1.36-35.52, p = 0.019) had higher risk for colonization of ertapenem-resistant Escherichia coli colonization. The patients who received treatment of ertapenem may have a lower risk of rectal colonization for ertapenem resistant Escherichia coli than those who received flomoxef or moxifloxacin. The rate of Pseudomonas colonization did not differ between the three study Pseudomonas-sparing agents.