Figure 4. Proportions of Pseudomonas aeruginosa (A) and Acineto- bacter baumannii (B) isolates causing nosocomial infections resistant to imipenem in National Taiwan University Hospital, 1993-1999. ICU = intensive care unit. stable (4% to 11%), higher incidences of imipenem-resistant P. aeruginosa or A. baumannii were found in ICUs than in gen- eral wards in most time periods. Since 1990, Candida species have continued to be an important cause of nosocomial BSI in the United States, and the proportion (40%-50%) of these infections due to species of Candida other than C. albicans may be increasing (12,19,20,31,32). Among the species of Candida other than C. albicans, C. glabrata (prone to be resistant to fluconazole) and C. krusei (intrinsically resistant to fluconazole) are of clinical importance (31,33). Although the proportion (40%) of candi- demia due to non-albicans Candida species in 1999 in our hos- pital was similar to that (48%) reported in the United States from April 1995 to June 1996, the incidences of C. glabrata (8.8%) and C. krusei (0%) in our hospital were lower than those (20% and 5%, respectively) in the United States (31). Although an upsurge in the incidences of K. pneumoniae and E. coli isolates resistant to cefotaxime was noted in our ICUs, an investigation is under way into the mechanisms of resistance and potential outbreaks (clonal dissemination or gene transfer) (34). The abrupt increase in the proportion of A. baumannii isolates resistant to imipenem in 1999 resulted from RESEARCH wide dissemination of several multidrug-resistant clones in ICUs and many general wards in the hospital (data not shown). In summary, surveillance of the microbial etiology of nososcomial infections over prolonged time periods not only can provide important information for day-to-day decision making in antimicrobial therapy in individual hospitals but also can reflect local trends and shifts in etiology and antimi- crobial drug resistance. Nosocomial pathogens have shifted away from easily treated bacteria toward more resistant bacte- ria and even to Candida species with fewer options for therapy. These shifts continue to present challenges for nosocomial infection control and prevention. Dr. Hsueh is an assistant professor in the departments of Labora- tory Medicine and Internal Medicine, National Taiwan University College of Medicine. His research interests include epidemiology of emerging and nosocomial infections and mechanisms of antimicrobial drug resistance. 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