Vancomycin MICs and risk of complicated bacteremia by glycopeptide-susceptible Staphylococcus aureus

AbstractVancomycin (VAN) minimum inhibitory concentrations (MICs) at the upper end of the susceptible range forStaphylococcus aureus (S. aureus), as measured by the Etest method, have been associated with poor clinical outcomes ofS. aureus bloodstream infections, as has the isolate ’s genetic background. Here, we assessed the impact of VAN MICs, as determined by a broth microdilution method (BMD) that incorporates incremental VAN concentrations between the conventional log2 dilutions, isolate susceptibility to killing by human phagocytes, acting as a surrogate marker for bacterial cell wall thickness, andS. aureus genetic composition, on the development of complicatedS. aureus bacteremia (SAB). We carried out a retrospective, observational single-center cohort study of 148 consecutive patients with SAB caused by methicillin-susceptible (MSSA) isolates (n = 113) or methicillin-resistant (MRSA) isolates (n = 35).S. aureus isolates were genotyped using a commercially available DNA microarray. Overall, VAN MICs ofS. aureus isolates taken from complicated and uncomplicated SAB were comparable, irrespective of the testing method (P = 0.19 with BMD, andP = 0.94 with Etest). Likewise,S. aureus isolates in both comparison groups had the same susceptibility to killing by human phagocytes (P  = 0.5). Among the genes screened by theS. aureus DNA array, onlySec andSel were differentially present amongS. aureus isolates in both groups (overrepresented in those causing ...
Source: European Journal of Clinical Microbiology and Infectious Diseases - Category: Microbiology Source Type: research