Answer Happy

Case Study #7: Beauty and the (Bacterial) Beast After an intense mountain bike crash that left his nose disfigured, Josh decided to have reconstructive surgery. A few days after surgery Josh was changing the dressings of gauze on his nose when he noticed increased swelling and pain at the incision site. By the next day he had a fever above 100°F. Josh went back to the surgery clinic, where they took a swab of pus from the infected area for culture and prescribed an antibiotic. The next day the lab called to report that Josh had a Staphylococcus aureus infection. The surgery and the nasal packing with gauze provided both an area for bacterial proliferation and an environment that contained air pockets giving the bacteria necessary amounts of oxygen for growth. S. aureus is a gram positive, nonmotile, catalase positive, coccus found on the outside of the body, especially around the nose. About 30% of the population carries S. aureus at any particular time, and about 2/3 of people are at least occasional carriers. The bacteria can induce localized inflammation that causes capillary endothelial cell damage and gives the bacteria access to the circulation. S. aureus produces an antiphagocytic capsule and surface adhesins. In addition to catalase, it also secretes protease, lipase, and hyaluronidase that destroy tissue, and coagulase that converts fibrinogen to a fibrin clot inside which the bacteria can grow. Many strains of S. aureus produce exotoxins and some strains are antibiotic resistant. Fortunately for Josh, the S. aureus infecting his nose did not produce toxic shock syndrome toxin or exfoliative toxin, and together with the antibiotics his body was able to clear the infection. Case Questions: 1. How did Josh's immune system first respond to the bacteria? Briefly summarize, in approximate chronological order, the steps in the innate response to a bacterial infection. Include both the cells and the molecules that are involved in the response to the bacteria and what each does. 2. How do phagocytes eliminate pathogens? What group of pathogens are most easily phagocytosed and why? 3. What is inflammation, and what is its purpose? What are the four signs/symptoms and what causes them? 4. What is complement? In what ways is complement activation initiated and what are the functions of complement? 5. What are acute phase proteins and how do they enhance innate immunity?