RESEARCH Methicillin-resistant Staphylococcus aureus Methicillin-resistant CoNSa Penicillin-resistant enterococci Gentamicin-resistant enterococci Cefotaxime-resistant Escherichia coli Cefotaxime-resistant Klebsiella pneumoniae Cefotaxime-resistant Enterobacter spp. Cefotaxime-resistant Pseudomonas aeruginosa Imipenem-resistant P. aeruginosa Ciprofloxacin-resistant P. aeruginosa Imipenem-resistant Acinetobacter baumannii aCoNS = coagulase-negative staphylococci; = not available. Discussion Hospitals worldwide are continuing to face the crisis of the upsurge and dissemination of antimicrobial-resistant bacteria, particularly those causing nosocomial infections in ICU patients (1,27-29). Among resistant bacteria, MRSA, MRCoNS, VRE, third-generation cephalosporin-resistant Enterobacteriaceae, and imipenem- or ciprofloxacin-resistant P. aeruginosa and A. baumannii are of great concern because these bacteria have spread worldwide and ultimately will com- promise the antimicrobial therapy of infections caused by these organisms (2,25-28,30). This report describes trends in major nosocomial pathogens and shifts in antimicrobial resistance during a 19-year period in a large teaching hospital in Taiwan. In a comparison of data from a recent NNIS study and other surveillance systems 1981-1986 20.2/27.8/19.5 72.2/88.2/70.8 5.9/6.8/5.8 0.0/0.0/0.0 1.6/0.0/1.7 4.9/8.8/3.9 35.8/52.4/32.4 24.2/20.0/25.0 1987-1992 31.4/58.5/26.6 74.0/83.9/71.5 20.7/30/19.6 71.0/71.4/70.9 2.8/8.6/2.5 7.4/16.9/5.6 49.7/55.7/47.7 16.1/24.3/12.1 1993-1998 64.8/86.9/56.7 79.0/88.7/75.1 19.5/22.6/18.7 61.5/67.2/60.0 6.8/13.1/6.2 22.8/50.5/15.6 57.6/67.0/53.6 10.2/16.9/7.8 8.5/18.2/4.9 8.7/11.6/5.8 6.7/9.1/4.4 1999 69.3/87.4/60.2 90.6/90.9/90.5 35.9/40.9/27.8 50.0/39.3/55.2 12.3/10.3/12.7 16.5/40.0/9.3 50.9/61.8/46.2 11.2/17.6/8.1 6.7/4.5/7.7 14.0/18.2/2.9 12.5/23.3/7.6 (2,4,9,31), our results suggest four conclusions. First, Candida species, rather than P. aeruginosa, E. coli, or staphylococci, now are the most frequent pathogens causing overall nosoco- mial infections and BSIs in this hospital. The upward trend in coagulase-negative staphylococci, which was the leading cause of BSI in the recent NNIS study, was not confirmed in our study. Second, we observed a remarkably high incidence of MRSA, especially in ICUs, contrasted with a relatively low incidence of VRE. Third, we report an increase in incidence of cefotaxime-resistant Enterobacteriaceae, especially in the inci- dence of cefotaxime-resistant K. pneumoniae in ICUs. Fourth, although the overall incidence of imipenem resistance among P. aeruginosa and A. baumannii in recent years has remained Table 2. Selected antimicrobial resistant pathogens associated with nosocomial infection at National Taiwan University Hospital from 1981 to 1999 Resistant pathogen % resistance (all patients/in intensive care unit patients/in patients in general wards) Figure 2. Changes in major antimicrobial-resistant nosocomial patho- gens in relation to ceftazidime use at National Taiwan University Hospi- tal from 1991 to 1999. Figure 3. Incidences of vancomycin-resistant enterococci (VRE) among all enterococcal isolates causing nosocomial infections in relation to vancomycin use at National Taiwan University Hospital, 1995-1999. Numbers above the bars denote the number of enterococcal isolates causing nosocomial infections. Numbers within the bars denote the numbers of VRE. 66 Emerging Infectious Diseases • Vol. 8, No. 1, January 2002