Case 1 Troy, a high school wrestler, cut himself on a piece of broken fence whil

Question

Case 1 Troy, a high school wrestler, cut himself on a piece of broken fence while playing basketball with some friends at the park. While at wrestling practice the next day, his wound opened up and he lost the bandage covering it. He replaced the bandage with one from the coach and continued practicing. The next day Troy woke with a swollen, reddened leg. The wound had pimples around it and oozed pus and fluid. The wound was painful and it was hard for him to walk. He felt nauseous and vomited. Troy went to school, but had to leave early because his leg hurt and kept oozing fluids. The bandage became soaked. The nausea also would not let up. He was running a fever of 103°F. He was transported to the emergency room for treatment of his wound and other symptoms. He was diagnosed with an MRSA infection and treated with vancomycin. He stayed in the hospital for 2 days before returning home. 1. What are some possible ways Troy could have been infected with the bacterium? (sources) 2. What might have been done differently to prevent the infection? 3. Was the nausea and vomiting related to the MRSA infection? Why/why not? 4. Describe how vancomycin works? 5. Describe how Staphylococcus aureus invades tissue and might lead to sepsis. Case 2

Explanation / Answer

1. The bacterium infections could be through direct contact with wounds, discharge and soiled areas. Other possibility of infection due to the breaks in the skin due to wounds, poor personal hygiene or living in crowded conditions.

2. He should not have practiced the day after the infection, due to which he has exposed the wound. This led to the aggravation of infection with MRSA.

3. Nausea and vomiting was not caused due to MRSA, but it is a side effect for the usage of Vancomycin antibiotic.

4. Vancomycin is a glycopeptide antibiotic produced by Streptomyces bacteria. It prevents the NAM and NAG from being incorporated into the peptidoglycan matrix.

5. Staphylococcus aureus adheres to cells and extracellular matrix components by the joint action of MSCRAMM (microbial surface component recognizing adhesive matrix molecules) and secreted expanded repertoire adhesive molecules. MSCRAMMs bind molecules such as collagen, fibronectin and fibrinogen, and different MSCRAMMs may adhere to the same host-tissue component. Thus, these molecules act in the initiation of endovascular infections, endocarditis and bone and joint infections. By the heterogeneity of MSCRAMMs types, different S. aureus strains may be predisposed to causing certain kinds of infections (78a). Coagulase is an extracellular protein, belonging to the secreted expanded repertoire adhesive molecules class, which binds to prothrombin to form a complex called staphylothrombin. The protease activity of the thrombin complex is activated, resulting in the conversion of fibrinogen to fibrin.

The -toxin is expressed as a monomer that binds to the eukaryotic cell membranes, the subunits oligomerize to form heptameric rings with a central pore through which cellular contents leak. This toxin also induces the death of innate and acquired immunity cells, interferes with the metabolism of arachidonic acid, exocytosis and induces dysfunctions in contractility, leading to bacterial spread and alterations of the hemostasis

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