Abstract
BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) is an increasingly prevalent pathogen capable of causing severe vascular infections. The goal of this work was to investigate the role of shear stress in early adhesion events.MethodsHuman umbilical vein endothelial cells (HUVEC) were exposed to MRSA for 15-60 minutes and shear stresses of 0-1.2 Pa in a parallel plate flow chamber system. Confocal microscopy stacks were captured and analyzed to assess the number of MRSA. Flow chamber parameters were validated using micro-particle image velocimetry (PIV) and computational fluid dynamics modelling (CFD).ResultsUnder static conditions, MRSA adhered to, and were internalized by, more than 80% of HUVEC at 15 minutes, and almost 100% of the cells at 1 hour. At 30 minutes, there was no change in the percent HUVEC infected between static and low flow (0.24 Pa), but a 15% decrease was seen at 1.2 Pa. The average number of MRSA per HUVEC decreased 22% between static and 0.24 Pa, and 37% between 0.24 Pa and 1.2 Pa. However, when corrected for changes in bacterial concentration near the surface due to flow, bacteria per area was shown to increase at 0.24 Pa compared to static, with a subsequent decline at 1.2 Pa.ConclusionsThis study demonstrates that MRSA adhesion to endothelial cells is strongly influenced by flow conditions and time, and that MSRA adhere in greater numbers to regions of low shear stress. These areas are common in arterial bifurcations, locations also susceptible to generation of atherosclerosis.
Highlights
Methicillin-resistant Staphylococcus aureus (MRSA) is an increasingly prevalent pathogen capable of causing severe vascular infections
MRSA adhered to Human umbilical vein endothelial cells (HUVEC) and was internalized In order to assess binding of MRSA to endothelium, experiments were first performed under static conditions to develop a method to quantify infection and to determine time dependence
This study demonstrated that MRSA adheres to endothelium in a shear dependent manner which may be affected by the non-uniform shear stress distribution over an undulating endothelial monolayer
Summary
Methicillin-resistant Staphylococcus aureus (MRSA) is an increasingly prevalent pathogen capable of causing severe vascular infections. Infections of the cardiovascular system, including those involving prostheses and devices, are a globally recurring problem. Infection is a common problem affecting the success of biomedical implants, such as vascular stents [1]. Cardiovascular disease has been linked to microbial infection [2,3], with attachment of bacterial pathogens to endothelium or extracellular matrix being an initial step in the process [4]. Staphylococcus aureus is a highly adaptable microbial pathogen that is considered to be a leading cause of various community- and hospital-acquired infections [5]. S. aureus is the primary cause of endovascular and endocardial infections that are extremely difficult to treat, with mortality rates between 40 and 50% at one year [7]. Of particular concern is the ability of S. aureus to become tolerant to antibiotic therapies, and to generate antibiotic resistant strains
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