Background : A rapid increase in antimicrobial-resistant bacteria has become a serious problem in Korea. Moreover, the antibiotic resistance problem has worsened noticeably during the past several years. The aim of this study was to determine the prevalence of resistance among frequently isolated gram-positive and -negative bacteria in Korea.

Methods : Routine susceptibility data for medically important bacteria isolated during 6 months of 2003 were collected from 12 university and general hospital laboratories in Korea. 

Results : The proportion of methicillin-resistant Staphylococcus aureus (MRSA) was 66%; however, vancomycin-resistant strains were not detected. The rates of vancomycin-resistant Enterococcus faecium and penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) were 22% and 73%, respectively. The resistance rates to 3rd generation cephalosporins and monobactam were: Escherichia coli 8-12%, Klebsiella pneumoniae 18-22%, Citrobacter freundii 22-32%, Enterobacter cloacae 34-37%, and Serratia marcescens 12-21%, respectively. Imipenem resistance rates of Acinetobacter baumannii and Pseudomonas aeruginosa were 23% and 25%, respectively.

Conclusions : Antimicrobial resistant strains were already prevalent among the clinically important isolates, especially, MRSA, PNSP, and extended-spectrum cephalosporin resistant gram-negative bacilli in Korea. The imipenem-resistant rates of A. baumannii and P. aeruginosa increased, respectively, from 13% and 20% in 2002 to 23% and 25% in 2003. The results of this study will provide a basis for proper treatment of bacterial infections and prevention of spread of resistant bacteria. A continuous nationwide surveillance of antimicrobial resistance is very important and should be performed. (Korean J Clin Microbiol 2004;7(2):171-177)