Comparison of antimicrobial susceptibility of Citrobacter freundii isolates in two different time periods.

Citrobacter freundii was first identified in 1932, since then it has been reported to cause a variety of infections in aged, immunocompromised, and debilitated patients. With the use of broad-spectrum antibiotics, C. freundii has become increasingly resistant to antimicrobial agents. In order to determine the chronological changes in susceptibility and current susceptibility status of C. freundii, we compared the antimicrobial susceptibility of C. freundii in two different time periods, from 1987 to 1988 and from 1997 to 1998. In both time periods, 61 isolates of C. freundii were randomly selected for study from all clinical isolates at National Taiwan University Hospital. The minimum inhibitory concentrations and susceptible rates of 15 antimicrobial agents were compared, and it was found that most C. freundii isolates were resistant to anti-pseudomonal penicillins, first, second, and third generation cephalosporins, gentamicin, tobramycin, and aztreonam. The results indicate that the susceptible rates of C. freundii to aminoglycosides and ciprofloxacin decreased markedly during the period from 1987 to 1998. Cefepime, cefpirome, imipenem, and meropenem remained the most active agents against C. freundii.