Prevalence and Clinical Implications ofStaphylococcus aureuswith a Vancomycin MIC of 4µg/ml in Korea

Abstract

In addition to vancomycin-intermediate Staphylococcus aureus (VISA), S. aureus with a vancomycin MIC of 4 microg/ml has been reported to be the cause of therapeutic failure. This study was designed to determine the prevalence of methicillin-resistant S. aureus (MRSA) with a vancomycin MIC of 4 microg/ml and to clarify the clinical characteristics of infections caused by these isolates. During the 8-week period from April to May, 2001, 27 hospitals participated in a nationwide surveillance program for VISA and vancomycin-resistant S. aureus (VRSA) in Korea. After screening on brain-heart infusion agar containing 4 microg/ml of vancomycin as previously described, 100 isolates with confluent growth were tested. The medical records of the patients involved were reviewed. Even though VISA or VRSA was not detected among 3,756 MRSA isolates, 18 (0.5%) had a vancomycin MIC of 4 microg/ml. The infections in 12 of these patients, excluding 5 that were colonized, were 8 chronic osteomyelitis, 1 surgical site infection, 1 pneumonia, 1 intra-abdominal infection, and 1 catheter-related infection. Although 11 cases were exposed to glycopeptides for a long time (median 56 days), the site of infection became culture-negative in only 1 case. Two patients died of their S. aureus infections. MRSA with a vancomycin MIC of 4 microg/ml was rare. Chronic osteomyelitis was the most common type of infection, and prolonged exposure to glycopeptides was associated with reduced susceptibility to vancomycin.

Clinical and Molecular Characterization of Invasive Heteroresistant Vancomycin-Intermediate Staphylococcus aureus Infections in Korean Hospitals

“…However, the multicenter design and the enrollment of a relatively large number of ISA cases in a prospective manner are important factors when considering differences between our results and those of studies performed at the level of individual centers. The prevalence of h-VISA among ISA infections was low in our study, which is in agreement with previous nationwide surveillance studies of clinical isolates (2,3). However, the prevalence of h-VISA in a recent study by Park el al.…”

“…showed that h-VISA was very rare in Korea (2,3). However, the prevalence of h-VISA among cases of methicillin-resistant S. aureus (MRSA) bacteremia reached 37.7% in a recent study performed in a Korean hospital (4).…”

Surveillance of Antibacterial Resistance in <i>Staphylococcus aureus </i>Isolated in Kuwaiti Hospitals

“…This is significant because to date only MRSA isolates have been reported with reduced susceptibility to vancomycin [24][25][26][27] . S. aureus isolates with reduced vancomycin susceptibility is clinically significant because these isolates have been shown to express heterogeneous resistance to vancomycin that resulted in treatment failure [26,27] . In heterogeneous resistance, a subpopulation of cells expresses resistance, whereas the majority of the cells appear susceptible.…”

In vitro ability of Staphylococcus aureus isolates from bacteraemic patients with and without metastatic complications to invade vascular endothelial cells

“…Antibiotic susceptibility was determined by the disc diffusion method, as recommended by the CLSI (2005). PFGE was performed as described previously (Kim et al, 2006).…”

“…Antibiotic susceptibility was determined by the disc diffusion method, as recommended by the CLSI (2005). PFGE was performed as described previously (Kim et al, 2006).Preparation of endothelial cells. Human umbilical vein endothelial cells (HUVECs) were used in these experiments.…”