The link between administration of antibiotics and detection of third-generation-cephalosporin-resistant (TGCR) enterobacteriaceae in faeces was studied in patients in a burns intensive care unit (ICU). The presence of extended-spectrum β-lactamase producers was also determined in these isolates.

At least two rectal swab samples were taken from 43 of 72 patients admitted to the ICU from January 1998 to June 1999. Antibiotic resistance tests were performed for all isolated enterobacteriaceae using the methods of the National Committee for Clinical Laboratory Standards. Only 10 out of 30 antibiotic-treated patients showed TGCR enterobacteriaceae in faeces. Fisher's exact test showed a relationship between the administration of oxyiminocephalosporins (third-generation cephalosporins) (P=0.002) or carbapenems (P=0.003) and the isolation of TGCR enterobacteriaceae from faeces. The administration of oxyiminocephalosporins led to the selection of resistant strains in the faecal flora.