The burden of nosocomial staphylococcus aureus bloodstream infection in South Korea: a prospective hospital-based nationwide study.

BACKGROUND: We estimated the nationwide burden of nosocomial S. aureus bloodstream infection (SA-BSI), a major cause of nosocomial infection, in South Korea. METHODS: To evaluate the nationwide incidence of nosocomial SA-BSI, cases of SA-BSI were prospectively collected from 22 hospitals with over 500 beds over 4?months. Data on patient-days were obtained from a national health insurance database containing the claims data for all healthcare facilities in South Korea. The additional cost of SA-BSI was estimated through a matched case?control study. The economic burden was calculated from the sum of the medical costs, the costs of caregiving and loss of productivity. RESULTS: Three hundred and thirty nine cases of nosocomial SA-BSI were included in the study: 254 cases of methicillin-resistant SA-BSI (MRSA-BSI) and 85 cases of methicillin-susceptible SA-BSI (MSSA-BSI). Death related to BSI occurred in 81 cases (31.9%) of MRSA-BSI and 12 cases (14.1%) of MSSA-BSI. The estimated incidence of nosocomial MRSA-BSI was 0.12/1,000 patient-days and that of nosocomial MSSA-BSI, 0.04/1,000 patient-days. The estimated annual cases of nosocomial BSI were 2,946 for MRSA and 986 for MSSA in South Korea. The additional economic burden per case of nosocomial SA-BSI was US $20,494 for MRSA-BSI and $6,914 for MSSA-BSI. Total additional annual cost of nosocomial SA-BSI was $67,192,559. CONCLUSION: In view of the burden of nosocomial SA-BSI, a national strategy for reducing nosocomial SA-BSI is urgently needed in South Korea.

The microbiological characteristics of Staphylococcus aureus isolated from patients with native valve infective endocarditis.

The microbiological characteristics of Staphylococcus aureus causing infective endocarditis (IE) have not been investigated thoroughly. We compared the characteristics of S. aureus isolates from patients with and without IE. Cases of S. aureus bacteremia (SAB) were collected from 10 hospitals over 7 years. Cases of native valve IE were matched with non-IE controls according to the following criteria: central-line-associated infection, community-acquired infection, methicillin susceptibility, and if possible, the primary site of infection. Genes coding virulence factors were analyzed using multiplex polymerase chain reactions. Fibrinogen and fibronectin-binding properties were assessed using in vitro binding assays. The fibronectin-binding protein A gene (fnbpA) was sequenced. Of 2,365 cases of SAB, 92 had IE. After matching, 37 pairs of S. aureus isolates from the IE cases and non-IE controls were compared; fnbpA was detected in 91.9% of the IE isolates and 100% of the non-IE isolates (p = 0.24). While the fibrinogen binding ratio was similar (1.07 ± 0.33 vs. 1.08 ± 0.26, p = 0.89), the fibronectin-binding ratio was significantly higher in the IE-group (1.31 ± 0.42 vs. 1.06 ± 0.31, p = 0.01). The proportions of major single-nucleotide polymorphisms in fnbpA were as follows: E652D (2.9% vs. 2.7%), H782Q (65.6% vs. 60.6%), and K786N (65.6% vs. 72.7%). The fibronectin-binding ratio was positively correlated with the number of SNPs present in IE cases (p < 0.001) but not in the non-IE controls (p = 0.124). Fibronectin-binding might play a key role in SAB IE. However, the degree of binding may be mediated by genetic variability between isolates.