Microorganisms isolated from blood cultures and their antimicrobial susceptibility patterns at a university hospital during 1994-2003

BACKGROUND: Blood culture is important for the determination of the etiologic agent of bacteremia. Analysis of blood culture results and antimicrobial susceptibility trend can provide clinicians with relevant information for the empirical treatment of patients. METHODS: The species and antimicrobial susceptibility of the isolates from blood cultures at the Severance Hospital during 1994-2003 were analysed. Blood specimens were cultured for 7 days using tryptic soy broth and thioglycollate medium. Identification of organism was based on conventional methods or commercial kit systems. Antimicrobial susceptibility was tested by a disk diffusion method. RESULTS: Of 536,916 blood specimens cultured, 24,877 (4.6%) from 13,102 patients were positive. Among the isolates, 93.1% were aerobic or facultative anaerobic bacteria, 3.3% anaerobes, and 3.6% fungi. Escherichia coli was isolated most frequently, followed by Staphylococcus aureus, alpha-hemolytic Streptococcus, Enterococcus spp., and Klebsiella pneumoniae. The proportion of patients with Enterococcus faecium and K. pneumoniae gradually increased during this study. Enterococcus, S. aureus and alpha-hemolytic Streptococcus were frequently isolated from the age group of less than 2 yr. E. coli, Enterococcus spp., K. pneumoniae and S. aureus from the age group of over 50 yr. Oxacillin-resistant S. aureus decreased, whereas vancomycin-resistant E. faecium and imipenemresistant Pseudomonas aeruginosa and Acinetobacter baumannii increased. CONCLUSIONS: E. coli was the most common cause of bacteremia and S. aureus, alpha-hemolytic Streptococcus, and K. pneumoniae were frequently isolated pathogens. The bacteremia due to Enterococcus, K. pneumoniae, fungi, vancomycin-resistant E. faecium, and imipenem-resistant P. aeruginosa and A. baumannii gradually increased during this period.