Increase of antimicrobial resistance of faecal aerobic Gram-negative bacteria in a geriatric hospital

Antimicrobial resistance of faecal aerobic Gram-negative bacteria to eight different antimicrobials was determined by a velvet replica-plating method in 1988 and 1993. Faecal samples were taken from 131 geriatric inpatients in the Turku City Hospital with a hospitalization of more than 7 days. From 1987 to 1992 the use of first and second generation cephalosporins and ciprofloxacin increased from 3.32 defined daily doses (DDD) per bed to 24.25 DDD/bed and from 0.63 DDD/bed to 28.11 DDD/bed, respectively. A statistically significant increase was observed in the frequency of samples resistant (with greater than or equal to 1% of resistant colonies) to cefuroxime (p = 0.0004) and ceftazidime (p = 0.037) in patients who received antimicrobial therapy and to ampicillin (p = 0.046) in patients who had not received antimicrobial therapy. In addition, despite the decreased use of sulphonamides and trimethoprim (from 17.11 DDD/bed to 5.54 DDD/bed) no significant changes in the frequency of resistant faecal samples were observed. Use of ciprofloxacin has been found to eliminate resistance plasmids from bacteria in vitro. However, despite the increased use of ciprofloxacin, no decrease in faecal bacteria resistant to any of the other antimicrobials (i.e. trimethoprim) studied was observed.