title: Evaluation of in vitro susceptibility trends to vancomycin and daptomycin by strain type of Staphylococcus aureus causing bloodstream infections.
abstract: In total, 718 consecutive clinical meticillin-resistant Staphylococcus aureus (MRSA) isolates from 2006 to 2010 and 417 clinical meticillin-susceptible S. aureus (MSSA) isolates from mid-2007 to 2010 were evaluated. Isolates were from blood cultures obtained from separate patients in Detroit, MI, and were tested for in vitro susceptibility trends to vancomycin and daptomycin by molecular strain type. The MRSA pulsed-field gel electrophoresis (PFGE) results showed that 290 (40.4%) were USA100, 296 (41.2%) were USA300 and the remaining isolates were non-USA100/300. Vancomycin minimum inhibitory concentrations (MICs) by Etest [mean±standard deviation (S.D.) 1.55±0.26mg/L] in MRSA isolates showed no significant change over the 5-year period within all strain types, whilst daptomycin MICs by Etest (mean±S.D. 0.51±0.25mg/L) showed a significant downward trend across time (r=-0.243; P<0.001), with this trend occurring among all PFGE groups. For MSSA, a significant decrease in MICs to vancomycin was found by Etest (r=-0.160; P=0.001) and conversely a significant increase in daptomycin MICs by Etest was found (r=0.146; P=0.028). The results of this study showed that changes in MIC were not specific to strain molecular type. For vancomycin, there was no change in MRSA MICs and a decrease in MSSA MICs for blood isolates. For daptomycin, MICs decreased in MRSA and increased in MSSA blood isolates over the study period.
authors.affiliation: Division of Infectious Diseases, Henry Ford Health System, Detroit, MI, USA. Electronic address: nadeyinka@yahoo.com.
authors.forename: Adenike
authors.initials: A
authors.lastname: Shoyinka
authors.affiliation: Division of Infectious Diseases, Henry Ford Health System, Detroit, MI, USA.
authors.forename: Daniela
authors.initials: D
authors.lastname: Moreno
authors.affiliation: Division of Infectious Diseases, Henry Ford Health System, Detroit, MI, USA.
authors.forename: Samia
authors.initials: S
authors.lastname: Arshad
authors.affiliation: Division of Infectious Diseases, Henry Ford Health System, Detroit, MI, USA.
authors.forename: Mary B
authors.initials: MB
authors.lastname: Perri
authors.affiliation: Division of Infectious Diseases, Henry Ford Health System, Detroit, MI, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Donabedian
authors.affiliation: Division of Infectious Diseases, Henry Ford Health System, Detroit, MI, USA.
authors.forename: Gordon
authors.initials: G
authors.lastname: Jacobsen
authors.affiliation: Division of Infectious Diseases, Henry Ford Health System, Detroit, MI, USA.
authors.forename: Pamela
authors.initials: P
authors.lastname: Hartman
authors.affiliation: Division of Infectious Diseases, Henry Ford Health System, Detroit, MI, USA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Ziegler
authors.affiliation: Midwestern University College of Pharmacy-Glendale, Glendale, AZ, USA.
authors.forename: Vanthida
authors.initials: V
authors.lastname: Huang
authors.affiliation: Division of Infectious Diseases, Henry Ford Health System, Detroit, MI, USA; Wayne State University School of Medicine, Detroit, MI, USA.
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Zervos
keywords: Bacteraemia; Daptomycin; MIC; Staphylococcus aureus; Vancomycin