The evaluation of vancomycin microspheres in sepsis induced by Staphylococcus aureus

Bacterial pathogenesis is highly dependent on the ability of organisms to colonize host tissues. Staphylococcus aureus ( S. aureus) is generally considered an extracellular pathogen compared to other facultative intracellular organisms such as Listeria, Salmonella, and Mycobacteria. However, adherence to endothelial cells (EC) by S. aureus can lead to internalization of the bacteria by the EC. The consequence of bacterial internalization is not exactly known. The survival and replication of S. aureus within endothelial cells (where they are protected from host defenses and antibiotics) plays an important role in the frequency and persistence of invasive staphylococcal infections. Bovine serum albumin microspheres of vancomycin were prepared by the spray drying method, using glutaraldehyde as the crosslinking agent. Endothelial cells were exposed to both S. aureus and drug-loaded microspheres. Three treatment groups were studied: Prophylactic, simultaneous, and delayed treatment.; In the prophylactic treatment, encapsulated vancomycin decreased the intracellular bacterial load by 73%, while the solution form decreased the bacterial load by 32% after 5 hours of incubation. In vitro treatment of HMEC's immediately after S. aureus internalization resulted in a 57% decrease in bacterial load by vancomycin microspheres as compared to a 37% decrease by vancomycin solution, after 24 hours of incubation. In vivo experiments showed a similar trend of results.; The general hypothesis is that, in bacterial induced sepsis, both internalized and circulating bacteria compromise the integrity of the vasculature. Experiments were performed to prove this assumption. Bacteria which were internalized were later exocytosed. The number of exocytosed bacteria increased with time. The effect of bacteria and their cell wall products on vascular permeability was also evaluated using a fluorescent marker. The effect of Lipoteichoic acid (LTA), peptidoglycan (Pep G), Lipopolysaccharide (LPS), and S. aureus on the permeability of various molecular weight compounds through an endothelial cell monolayer was evaluated. All the compounds used were more effective than the control (1% HBSS) in increasing the permeation of FITC.; These results indicate that the drug-loaded albumin microspheres can be used to target all intracellular pathogens. This can result in lower dosage requirements, decreased toxicity, and more effective killing of pathogenic organisms.