Background: With the emergence and prevalence of new resistant bacteria, it is crucial to investigate the nationwide resistance rates. This study analyzed the antimicrobial resistance rates of major bacteria isolated from patients visiting 12 university and general hospitals nationwide during the first half of 2004.

Methods: The antimicrobial resistance rates of major bacteria isolated from 12 leading university and general hospitals nationwide were investigated. The antimicrobial susceptibility patterns of major bacteria isolated from clinical specimens between April and November 2004 were summarized for each institution and analyzed according to the patient’s hospitalization status.

Results: Methicillin-resistant Staphylococcus aureus (MRSA), a major nosocomial pathogen, was isolated at a rate of 67% overall and 86% in ICU patients. Vancomycin-resistant Enterococci (VRE) were found in 1% of Enterococcus faecalis and 20% of Enterococcus faecium. The proportion of penicillin-resistant Streptococcus pneumoniae was high at 70%. The ampicillin resistance rate of Haemophilus influenzae ranged from 40% to 63%, with an average of 54%, and the β-lactamase production rate was similar to the resistance rate. The resistance rates to third-generation cephalosporins were 7-10% in Escherichia coli and 26-31% in Klebsiella pneumoniae. The resistance rates for major nosocomial pathogens such as Citrobacter freundii, Enterobacter cloacae, and Serratia marcescens were 22-30%, 35-44%, and 15-22%, respectively. The resistance rates of Pseudomonas aeruginosa to imipenem and meropenem were 26% and 21%, respectively. The resistance rates of Acinetobacter baumannii to imipenem and meropenem were 17% and 32%, respectively, which were higher than those for other gram-negative bacilli. The resistance rates of Stenotrophomonas maltophilia to cotrimoxazole and levofloxacin were 46% and 44%, respectively.

Conclusion: In conclusion, the antimicrobial resistance rates of major pathogens isolated from clinical specimens of domestic patients remained high, with more resistant strains isolated from wards and ICU patients where there was a higher antimicrobial selection pressure than from outpatients. Regular nationwide surveys of antimicrobial resistance rates, along with the establishment of infection control measures to prevent the spread of resistant bacteria, are deemed necessary.

 (Korean J Clin Microbiol 2005;8(1):66-73)