Three-month-old, male, Crl:CD1 (ICR) BR mice were fed chow containing Candida albicans or regular chow. Subsequently, both groups were given either antibiotics or normal saline for 10 days. Stool cultures were performed immediately before administration, at the end of antibiotic administration, and 1 week after the discontinuation of antibiotics, to determine the effect on the concentration of C. albicans in the stools. The stools of mice fed C. albicans and given antibiotics had substantially higher Candida counts than those of control mice fed C. albicans and given saline. Significantly higher candidal concentrations were observed in the stools of mice given chloramphenicol compared with those of mice given ciprofloxacin, sulfamethoxazoletrimethoprim, and ampicillin. No mice developed histopathological evidence of local gastrointestinal invasion or disseminated candidiasis. In this mouse model, Candida colonization increases substantially after the administration of antimicrobial agents with broad spectra and anaerobic activities.Patients with cancer are at risk of developing disseminated candidiasis (3, 11). The gastrointestinal (GI) tract is the source of dissemination in many cases (3, 10). The administration of broad-spectrum antibiotics is associated with an increase in the concentration of Candida organisms in the GI lumen and hence may increase the risk of disseminated candidiasis (3, 14). We have previously described a mouse model of sustained GI colonization by Candida albicans (15). In the present study, we report on the effects of five antimicrobial agents on the level of GI colonization by C. albicans in the this mouse model. These agents were selected because of their frequent use in outpatient therapy, an approach that has gained increased interest recently.Groups of 50 Crl:CD1 (ICR) BR mice, 3 months old and weighing approximately 25 g each (Charles River Laboratories, Wilmington, Mass.), were used with each antibiotic. Thirty of the mice were fed chow containing C. albicans for 2 weeks. Details of the preparation of this chow have been reported previously (15). The remaining 20 were fed regular chow which did not contain C. albicans. GI colonization by C. albicans was verified 1 week after the end of the special diet period by stool cultures, as described previously (14,15). Subsequently, 20 mice of each group colonized with C. albicans received subcutaneous injections of the study antibiotics for 10 days. The antimicrobial agents used in this study were amoxicillinclavulanate, chloramphenicol, ciprofloxacin, sulfamethoxazoletrimethoprim, and ampicillin and were supplied by their commercial manufacturers. The dosage schedules were equivalent to those for humans and were calculated by the method of * Corresponding author. Mailing address:

A group of three-month old, male Crl:CD1(ICR) BR mice, was fed chow containing Candida albicans, while another group of the same type of mice was fed regular chow. Both groups were treated subsequently with either antibiotics or normal saline for 10 days. Stool cultures were performed before treatment, at the end of treatment, and one week after the end of treatment, to determine the level of colonization of the gastrointestinal tract by the yeast. The stools of mice fed Candida and treated with antibiotics had substantially higher Candida counts than control mice fed C. albicans and treated with saline. The highest concentrations of the yeast were observed in the stools of mice treated with cefotaxime as compared to those of mice treated with pefloxacin, amikacin and amoxicillin. No Candida was found in the stools of mice fed regular chow and treated with antibiotics or saline. Dissemination of Candida was not observed in the visceral organs of any mouse.